Prevalence, determinants, intervention strategies and current gaps in addressing childhood malnutrition in Vietnam: a systematic review

doi:10.21203/rs.3.rs-3227610/v1

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Prevalence, determinants, intervention strategies and current gaps in addressing childhood malnutrition in Vietnam: a systematic review

https://doi.org/10.21203/rs.3.rs-3227610/v1

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published 04 Apr, 2024

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Background

Childhood malnutrition in all forms is a major public health issue worldwide. This review aimed to systematically examine the prevalence and determinants, and identify the potential interventions and current gap in addressing malnutrition including undernutrition, overnutrition and micronutrient deficiencies (MNDs) in Vietnamese children aged 0–18 years old.

Methods

Embase, Scopus, PubMed, and Web of Science were systematically searched through June 2022 to identify relevant articles published within the past 25 years. Study selection and data extraction were performed by one reviewer and checked for accuracy by the other two reviewers in accordance with PRISMA guideline. Risk of publication bias was assessed using American Dietetic Association Quality Criteria Checklist.

Results

81 studies that met the inclusion criteria were included. Undernutrition have been decreased over time but still 22.4%, 5.2% and 12.2% of children under 5 were stunted, wasted and underweight, respectively. Prevalence of MNDs varied by age, regions or socio-economic groups, with 11.4–89.9%, 11–90%, 23–87%, 11–58% and 8–20% of Vietnamese children were anaemic and iron, zinc, vitamin D and retinol deficient, respectively. Overweight and obesity is now on the rise (7.4–22%). The key determinants of undernutrition/MNDs included living in rural areas, children with low birth weight, and poor socio-economic status, whereas living in urban and affluent areas, having an inactive lifestyle and being a boy were associated with increased risk of overweight or obesity. Nutrition specific intervention studies including supplementation and food fortification consistently showed improvements in anthropometric indices and micronutrient biomarkers, and national nutrition sensitive programmes also provided nutritional benefits on child’s growth and eating behaviours, but lack of data on childhood overweight.

Conclusion

Stunting is still prevalent at 20% in Vietnamese children (< 5years) despite a significant reduction over the decade. MNDs remain to be a serious problem, whilst overweight and obesity are rapidly rising requiring attention and intervention. This finding highlights the needs for double duty actions to simultaneously and effectively address different forms of childhood malnutrition in Vietnam. However, evidence on the potential intervention strategies, especially on MNDs and overnutrition are still limited to inform policy decision, thus future researches are warranted.

undernutrition

overnutrition

micronutrient deficiencies

prevalence and determinants

interventions

children and adolescents

Vietnam

Vietnam is a country located in the Southeast Asia, with an estimated population of 96 million. Since 1986, the government has introduced an economic reform, aiming to boost the country’s economic development (1). Vietnam is now one of the countries with fastest growing gross domestic product worldwide (2), and this has resulted in substantial decrease in poverty and undernutrition in the population. However, inequalities have arisen in social, health, and wealth whilst overnutrition has become an increasing burden (3).

Malnutrition encompasses undernutrition including micronutrient deficiencies (MNDs), and overnutrition. Undernutrition generally results from an inadequate consumption of energy and nutrients, and it can be classified into three groups according to World Health Organisation (WHO) definition: stunting (height-for-age Z-score (HAZ) <-2 SD median), underweight (weight-for-age Z-score (WAZ) <-2 SD median), and/or wasting (weight-for-height Z-score (WHZ) <-2 SD median) (4, 5). MNDs were mostly assessed by the concentration of blood or urinary biomarkers. Overnutrition is defined as an excess accumulation of body fat, often due to the imbalance between energy intake and expenditure. According to WHO definition: WHZ ≥ + 2 SD to ≤ + 3 SD for overweight and ≥ 3 SD for obesity in children aged < 5 years old and overweight is defined as a body mass index (BMI)-for-age Z-score (BAZ) > + 1 SD and ≤ + 2 SD and obesity as > + 2 SD in children aged 5–19 years old (6).

Malnutrition can lead to serious health consequences and increases the risk of child’s mortality and morbidity. Undernutrition affects every system in body, results in altered immune function, increased susceptibility to illnesses and its complications include increased respiratory tract infections, impaired cardiac function, and long-term cognitive development (4). The health consequences that arise from MNDs vary widely depending on the types and magnitudes of deficiency of such micronutrients, but can include xerophthalmia (dry eyes, night blindness), anaemia (fatigue and heart palpitations), and goitre (swelling of the neck). Overnutrition is associated with increased risk of diet-related non-communicable diseases such as cardiovascular disease, cancers, strokes, type 2 diabetes, and polycystic ovarian syndrome (7).

Prevalence of malnutrition in children still remains a public health issue in Vietnam. The latest General Nutrition Survey in 2019 reported that 19.6% and 16.8% of children aged < 5 and 5–19 years old were stunted, respectively, whereas and 19% of children aged 5–19 years old were overweight (8). A shift has been observed within the burden of malnutrition, with overweight and obesity becoming more prevalent (9, 10). Determinants that found to be associated with child’s malnutrition could be classified as distal (socioeconomic), intermediate (environmental or maternal) or proximal factors (individual) (11). Distal factors include the region of living, ethnicity, mother’s education and occupation, and household income. Intermediate factors were split into two types: environment such as household size, structure of house, latrine type, and water source, and maternal variables such as mother’s age at birth, mother’s BMI, and number of children. Proximal factors include quality of breastfeeding (duration and initiation time), birth weight, and health status.

Tackling malnutrition is one of the United Nations Sustainable Development Goals (SDG’s), specifically ‘Goal 2 – Zero Hunger’, and it needs joint efforts from multiple sectors and disciplines. This requires achieving food security, improving diet and nutrition, and promoting sustainable agriculture and consumption. In general, there are two different types of nutrition interventions: nutrition specific and nutrition sensitive (12). Nutrition specific interventions aim to address any immediate determinants of malnutrition, and these include supplementation and food fortification which mostly focusing on iron, zinc, folic acid or multiple micronutrients, as well as supporting exclusive breastfeeding, and diet diversification (12). The common fortified foods included biscuits, milk, noodles, rice, and flour. Whereas nutrition sensitive interventions aim to address the underlying root-causes of malnutrition, such as improving food security through agriculture support, nutritional education, safe drinking-water, sanitation and hygiene and improving healthcare access (13).

Given to its severeness, however, the malnutrition situation and the key drivers in Vietnamese children have still rarely been extensively and systematically reviewed, leading to an evidence gap on the extent and burden of malnutrition and its potential strategies. Therefore, this study aimed to systematically review the current evidence on the prevalence, determinants and intervention strategies of malnutrition including under nutrition (stunting, wasting and underweight), over-nutrition (overweight and obesity) and micronutrient status, particularly that of anaemia, iron, zinc, vitamin A, D and folate, in the Vietnamese children aged 0–18 years old.

This systematic review was conducted by three independent reviewers in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.

Inclusion and exclusion criteria

PI(E)CO (Participant, Intervention/ Exposure, Comparison and Outcome) framework (14) was used to guide the development of the inclusion and exclusion criteria of this systematic review, and the details are shown in Table 1. All observational studies, intervention trials and reviews reporting within the past 25 years on the prevalence, determinants, and interventions (including both nutrition sensitive and specific programmes) of malnutrition including undernutrition (e.g., stunting, wasting, underweight, thinness, height, weight, HAZ/length -for-age Z-score (LAZ), WAZ, WHZ/weight-for-length Z-score (WLZ) and mid upper arm circumference (MUAC)), overnutrition (e.g., overweight, obesity, body mass index (BMI), and waist and hip circumferences), and micronutrient deficiencies particularly focusing on anaemia, iron, zinc, and vitamins A, D and B9 (folate or folic acid), in Vietnamese infants, young children and adolescents aged 0–18 years old were searched.

Table 1

PI(E)CO criteria for inclusion and exclusion of studies
Criteria	Inclusion	Exclusion
Population (P)	Vietnamese infants, young children and adolescents aged 0–18 years old	Those who have been diagnosed with any chronic or congenital diseases that potentially affect the child’s nutritional status
Exposure (E) and intervention (I)	Any studies that reported the prevalence, determinants of childhood malnutrition, and interventions (including both nutrition specific and sensitive programmes) aiming to address childhood malnutrition	Studies assessing the genetic effects on malnutrition indicators; interventions targeted at mothers or pregnant women with no child outcomes; interventions that only reported the protocol with no outcomes
Comparison (C)	Those who do not exposed to the risk factors or interventions related to malnutrition	Not applicable
Outcome (O)	Malnutrition indicators including undernutrition (stunting, wasting, underweight and thinness), overnutrition (overweight and obesity) and micronutrient deficiencies which assessed by blood biomarkers such as iron (or ferritin, transferrin), vitamin A (or retinol), vitamin B9 (or folate/folic acid), anaemia (haemoglobin (Hb)), zinc, and iodine	Studies that do not assess malnutrition indicators as the primary outcomes or focused on the consequences of malnutrition

Search strategy

The literature search was performed through 29th June 2022 in four different databases including Embase, Scopus, PubMed, and Web of Science. Details of the search strategies for each database are reported in Table S1.

Study selection

Studies were exported from each database into EndNote (Endnote X7.7.1, Thomson Reuters 2016) and were screened by the three independent reviewers using the inclusion and exclusion criteria. When records were identified from all the four databases, the duplicates were removed. During the first stage of screening, all studies were filtered by title and abstract, and those which did not meet the inclusion and exclusion criteria were excluded. The full texts of the remaining records were accessed and screened using the same eligibility criteria. The final decision regarding the eligibility of articles was made by agreement between all reviewers. Disagreement between reviewers were resolved by discussion and by other reviewers when necessary.

Data extraction

Where available, the following information was extracted: the author and year of publication, study design and duration, participants’ characteristics including inclusion criteria, age and sample size, outcome measures (anthropometric parameters and micronutrient related blood biomarkers), intervention approaches (where appropriate), and key findings. In the case of missing data or unclear pieces of information, it was considered that the authors did not report such variables.

Data synthesis

The quantitative data from the studies included in this review was analysed. Data was extracted and tabulated based on three different topics of interests: the prevalence, determinants and the interventions that primarily aimed to address childhood malnutrition in Vietnam. Meta-analysis was not possible to be conducted due to the relatively smaller number of studies/sample size for each of these specific topics and the high heterogeneities across the studies in terms of the child’s age group, outcomes reported and intervention approaches (15).

The changes in the prevalence of malnutrition across the years were assessed, using larger-scale longitudinal cohort studies or repeated case control studies as these provide good representative information on the trend of the prevalence of malnutrition in specific age groups and locations. Determinants included those factors that found to be negatively or positively associated with different forms of malnutrition, the effect size of such associations (e.g., odd’s ratios (OR) or β-coefficient) were extracted and reported in the tables, and if it was not shown, the p-value was reported. With respect to interventions, the studies were further stratified into nutrition sensitive or nutrition specific interventions. The details of the interventions including the duration, sample’s characteristics, intervention approaches, control group (where applicable), and the key findings which assessed by the post-intervention changes in child’s anthropometric indices, or micronutrients biomarkers were reported.

Quality criteria checklist for risk of bias

The risk of bias was assessed for each study using a Quality Criteria Checklist from the Academy of Nutrition and Dietetics (16). This includes questions on (1) the research question clarity, (2) selection bias, (3) study group comparability, (4) withdrawal description, (5) blinding, (6) interventions, (7) study procedure description, (8) appropriate statistical analysis, (9) supported conclusions and limitations, and (10) sponsorship or funding bias. Depending on the answers to these questions, each study was assigned a negative, neutral, or positive rating. To be rated positive, five of the questions must be answered yes, including questions 2, 3, 6 and 7, and one other yes. The results of this were summarised in a horizontal stacked bar graph, showing the percentage of studies showing a low, medium, or high risk of bias for each question.

As shown in Fig. 1, the initial database search strategy identified a total of 2,326 records. This included 722 from Embase, 620 from PubMed, 571 from Scopus and 413 from Web of Science. Two additional records were identified from the reference list of records from the original search. After removing the duplicates, 411 records were screened by title and abstract to check for eligibility based on the inclusion and exclusion criteria. Of those, 242 articles were removed, and 169 full-text articles were assessed for eligibility. A final total of 81 articles which met the inclusion criteria were then included in this review.

Risk of bias assessment

The results for the risk of bias assessment are reported in Fig. 2. 80% of the records were classified as low risk of bias and 20% as unclear risk of bias. The common reasons for lower quality rating were typically the lack of blinding (69% of the records), lack of a withdrawal description (49%) and lack of randomisation or group comparability (17%). All studies stated that the research question, procedure, and the outcome measures have been sufficiently described.

Prevalence of different forms of malnutrition

Study’s characteristics

34 studies were identified reporting the prevalence of different forms of malnutrition (Table 2). These studies included cross-sectional (66%), longitudinal (31%), or review articles (3%). Studies reported the following data: undernutrition (11%, n = 4) (17–20), overnutrition (15%, n = 5) (21–25), MNDs (38%, n = 13) (26–37), undernutrition and overnutrition (24%, n = 8) (2, 38–44), and finally all three malnutrition types (3%, n = 1) (9).

The age groups varied across the studies and included children aged 0–18 years old. The average age range of participants was 5.3 years, and the majority of participants were preschool or primary school-aged children (80%). These studies collected anthropometric measurements including weight and height which were then used to calculate indices like HAZ, WHZ, WAZ, BAZ and/or BMI. These indices were used to classify individuals’ malnutrition status (overweight, obese, underweight, stunted or wasted). Micronutrients level were assessed by the blood biomarkers concentrations, and the deficiency status was mainly defined using WHO guidelines. 467,215 children were assessed over a period of 25 years, from 1988 to 2022.

Summary of the results

Table 2 shows the findings on the prevalence of malnutrition in Vietnamese children aged 2 months to 18 years old. Overall, the prevalence of overweight and obese children showed an increasing trend, especially in recent years. Prevalence of overweight and obesity in children aged 4–5 years old was almost doubled from 21.4% in 2002 to 36.8% in 2005 in the Ho Chi Minh City (41). A large cross-sectional study in Ho Chi Minh City of 10,949 children aged 6–18 years old reported that the prevalence of overweight and obesity in the urban region were 22%, and 19%, respectively in 2020 (44). Similar findings were reported in recent, smaller scale studies (~ 22%) among the preschool and primary school aged children (24, 25). Whereas in Hanoi, the prevalence of overweight increased from 9.1% in 2013 to 16.7% in 2016, although obesity was slightly reduced (-2%) (22).

The prevalence of undernutrition has generally decreased over the past 20 years. The largest longitudinal study reported a decrease in the prevalence of underweight by 18%, stunting by 25%, and wasting by 1.7% between 1990 and 2005 (18). Cross-sectional studies reported that in 2014–2015, 2.4%, 3.8% and 7.9% of the primary, secondary and high school aged children, respectively were stunted, and 2.2%, 4.6% and 6.0% were wasted (43, 44). The most commonly reported MNDs were iron, zinc, and vitamin A and D. The prevalence of each MND differed between studies, depending on the micronutrient investigated, age and locations. Anaemia was more prevalent in younger infants aged 6–11 months (38.6–89.9%) (45) and 0–6 years old (28.4–55.6%) (46), compared to older children aged 6–11 years old (11.4–18.2%) (47). Prevalence of iron deficiency varied greatly from 11% in the nationally representative South East Asia Nutrition Survey study (SEANUTs) to 90% in certain rural districts (33). Retinol deficiency was of less concern compared to other MNDs, ranged from 8–20% (2, 9). Zinc deficiency varied largely from 23–87% (2, 30), and vitamin D deficiency ranged from 11–58% (34, 35).

Determinant of different forms of malnutrition

Study’s characteristics

Out of a total of 35 records, 36% were nationally representative, 36% were in urban areas, 12% were in rural areas, 9% were in urban and rural areas (but not nationally representative), and 6% were in mountainous areas (Table 3). These include 575,193 children, with age ranged from 0–18 years old. Similarly, to the studies reporting the prevalence of malnutrition, the majority of the studied population were preschool and primary school-aged children (51%), followed by middle and high school-aged children (24%). This includes longitudinal (n = 15) and cross-sectional design (n = 19). Most studies collected anthropometric measurements (weight, height, and BMI) and questionnaires asking about lifestyle factors such as physical activity status or screen time. Demographic information was also collected in most questionnaires, including economic status, parents’ education level, occupation, or family size.

The studies examined the determinants of undernutrition (41%, n = 14) (11, 18, 20, 45–55), overnutrition (24%, n = 10) (24, 25, 39, 56–62), undernutrition and overnutrition (18%, n = 6) (44, 63–67), MNDs (9%, n = 3) (26, 68, 69), all three types of malnutrition (6%, n = 2) (9, 70), and undernutrition and MNDs (3%, n = 1) (71).

Summary of the results

The most commonly reported determinants for being underweight, stunted, or wasted in Vietnamese children were living in a rural area (OR = 2.22–4.50) (11, 63), having a low birth weight (LBW) (OR = 3.71–7.99) (11); low household wealth (20, 51), being a minority ethnic group (11), living in a mountainous area (18) and large household size (18). The risk of being overweight or obese is significantly higher in boys by 2.48 times (25), 1.39 times in physically inactive children (67), and 2.5 times in those living in urban areas (p < 0.05) (9). Other determinants of being overweight include living in a wealthy household (39), inactive mode of transport to school (25, 57), having overweight parents (66), and low food availability at home in girls only (66).

Few studies reported the determinants of MNDs, nonetheless iron deficiency was found to be associated with selenium deficiency (71), being underweight (70, 71), having malaria (68), and being a male (26).

Interventions and its impacts on addressing different forms of malnutrition

Study’s characteristics

21 articles reported intervention studies addressing different forms of malnutrition, mainly focusing on undernutrition and MNDs (Table 4), no intervention study was found addressing overnutrition. These include 4 nutrition sensitive and 17 nutrition specific programmes. Approximately 8,087 children participated in the intervention studies from 1996 to 2015, in addition to few large-scale studies evaluating the impacts of national government programme on child’s nutritional status. The duration of these studies ranged from 30 days to 2 years, and all of the studies were randomised control trials (RCT) except from one non-random pragmatic trial. A pragmatic trial is the one that carried out without a control/ placebo treatment (72). The interventions mainly targeted at younger aged children ranged from 0–8 years old.

Summary of the results

Most of the intervention studies demonstrated its effectiveness in improving child’s nutritional status, either through improved behaviours in the nutrition sensitive interventions, or improved anthropometric indices and micronutrients biomarkers in the nutrition specific interventions. Improved behaviours included increased breastfeeding, exclusive breastfeeding for longer duration, better weaning practices, children consuming more food and more hygienic practices (73, 74). Three nutrition sensitive studies showed significant reduction in the prevalence of severely malnourished (73), undernourished (74) and stunted children (75).

A follow-up study visited families with an older child who previously participated in an intervention study and received growth monitoring and positive deviance inquiry (73). Positive deviance involves identifying the children who, despite their poor socioeconomic status, but still enable to grow healthily. The behaviours, eating habits and lifestyles of these children are identified and shared with malnourished children, aiming to improve their nutritional status. In comparison to the control group, results showed that this intervention reduced severe malnutrition by 17%, and feeding habits improved significantly through more frequent feeding and better weaning practices. Another study used of positive deviant child practices alongside the promotion of breastfeeding, in malnourished children for two years (74). This resulted in children consuming more foods and being fed more frequently than the control group (p < 0.01), and children over 15 months old were more well-nourished (45.2%) than in the control group (29.6%, p < 0.01).

In a study of 368 infants aged 18–36 months, after consuming fortified milk containing vitamins and minerals for five months, the infant’s height was increased by 1 cm (p < 0.01), weight by 0.43 kg (p < 0.01) and BMI-Z score by 0.015 (p < 0.05) (76). Similarly, children (n = 1,080) gained significantly more weight (p < 0.001) and height (p = 0.008) compared to the control group, after receiving fortified biscuits and milk which provided an extra 300 kcal/day (77). Mixed results were seen in one study that provided participants with daily or weekly micronutrients, iron supplements or a placebo (78). LAZ and WAZ were worsened significantly in all groups, the LAZ in the daily multiple micronutrient group which was significantly less than in the placebo and weekly multiple micronutrient groups (p = 0.001), suggesting that children were not growing or putting on weight in line with their age group healthy counterparts.

Three studies investigated the impacts of providing supplementations to pregnant women e.g., iron, folic acid and multi-micronutrients on child’s nutritional status. Children of mothers who received multiple micronutrients supplementation were significantly taller than those receiving just iron and folic acid (p < 0.05), and the prevalence of stunting was significantly reduced (10%, p < 0.05) (79). Another study in 2015 also reported that infants were at a lower risk of anaemia if their mothers had taken the iron and folic acid supplement daily (OR = 0.31; 95% CI = 0.22–0.43), twice weekly (0.38; 95% CI = 0.26–0.54) or the multiple micronutrient (0.33; 95% CI = 0.23–0.48) during pregnancy compared to the placebo group (80). However, a different study reported no significant differences in birth weight or infant’s LAZ in pregnant women receiving supplementation of iron and folic acid daily or twice weekly, or a multiple micronutrient twice weekly (81).

One study investigated the impacts of iron, zinc, iron and zinc supplement or a placebo in 784 children aged 4–7 months old for six months (82). The combined iron and zinc supplementations significantly improved the levels of haemoglobin (Hb), ferritin, and zinc (p < 0.0001). Similarly, Hb concentrations improved, and the prevalence of anaemia was reduced in rural children aged 6–8 years receiving iron fortified noodles (p < 0.001) compared to the placebo group (83). Prevalence of iron deficiency and anaemia was significantly lower in infants with severe anaemia, after receiving fortified foods or complementary fortified foods for six months compared to the control group (p < 0.0001) (84, 85). Supplementing children with 10mg of zinc daily saw an increase in weight by 0.5 kg on average (+ 0.1 kg, p < 0.001) and height by 1.5cm on average (+ 0.2 cm, p < 0.001) (86)

Only one study investigated the effects of vitamin D and calcium supplementation using an uncontrolled trial (87), and the authors reported improved vitamin D concentrations (p < 0.001) and significant reduction in the prevalence of low bone mineral density (BMD) by 56.3% (p < 0.05). Another study investigated the effects of synthetic β-carotene supplementation (a precursor to vitamin A) or Momordica coincidences (gac) fruit which is locally available (88). After one month of intervention, both the interventions groups had significantly higher levels of β-carotene than the control group (p < 0.0001) and plasma retinol concentrations were significantly higher in the group receiving the fruit than the synthetic β-carotene (p < 0.01).

An evaluation study reported the success of the Government’s National Plan of Action for Nutrition (NPAN) and the National Targeted Programme on Hunger Eradication and Poverty Reduction (3) on improving child’s nutritional status. The NPAN involved a variety of poverty reduction initiatives, resulting in the nutritional status of the Vietnamese population improving considerably through reduction in the prevalence of underweight children and poor households, and increase in the income and food production.

Table 2

Findings on the prevalence of malnutrition (undernutrition, overnutrition and micronutrient deficiencies) in Vietnamese children aged 0–18 years old
Authors and year	Study design & duration	Sample age	Sample size	Measurements	Key findings - prevalence	Risk of bias
Dieu et al. 2009 (41)	Repeated cross sectional study 2002–2005 (3 years)	4–5 years	1,162 2002 = 492 2005 = 670	Weight, height, BMI Underweight = WAZ < 5th percentile Overweight/ obesity BMI > 23 kg/m²	36.8% obese (2005) 21.4% overweight 7.5% underweight Overweight/ obesity increased by 52.9% (p < 0.001)	Low
Do et al. 2017 (22)	Longitudinal 2013–2016 (3 years)	3–9 years	2,602	Weight and height	Overweight increased from 9.1–16.7% Obesity decreased from 6.4–4.5%	Low
Giao et al. 2019 (43)	Prospective cross-sectional	12–24 months	768 (receiving vaccinations)	Weight, height, HAZ and BMI-Z	8.2% stunted 10.7% overweight/ obese	Medium
Smuts et al. 2005 (2)	Cross-sectional	6–11 months	257	Weight, height, WAZ, HAZ, and WHZ Blood: serum levels of Hb, ferritin, retinol and zinc	12.7% low WAZ 8.0% low HAZ 3.0% low WHZ 89.9% anaemic 20.2% retinol deficient 22.5% zinc deficient	Low
Hall et al. 2001 (26)	Cross-sectional 1998	7–11 years	588	Blood: Hb levels	13% anaemic	Medium
Hong et al. 2007 (39)	Repeat cross- sectional study 2002 & 2004	11–16 years	3,687 2002 = 1,003 2004 = 2,684	Height, weight, and BMI-Z	Overweight significantly increased, 6.7% (p < 0.001) Obesity significantly increased, 1.4% (p < 0.001) Underweight decreased, 6.4% (insignificant) BMI significantly greater in 2004 than 2002 (p < 0.001)	Low
Hop et al. 1997 (17)	Longitudinal 1981–1994 (14 years)	0–10 years	212	Weight, height and feeding practices	Stunting at 21 months: 59.4% (male) & 58.3% (female)	Low
Huong et al. 2014 (42)	Cross-sectional	6 months-18 years	108	Weight, height and MUAC	19% wasted 13.9% stunted 0% obese 7% severe wasting at 6–59 months	Low
Khan et al. 2002 (27)	Review article	0–5 years	ND	Retinol deficiency = serum retinol < 0.70 µmol/L	10.8% retinol deficient	Low
Kim et al. 2022 (24)	Cross-sectional	3–4 years	103	Weight, height and BMI	22.3% overweight/ obese	Low
Le and Dinh 2022 (25)	Cross-sectional 2021	6–11 years	782	Height, weight and BMI-Z	14.32% obese 21.61% overweight	Low
Le Nguyen et al. 2016 (33)	Cross-sectional 2011 SEANUTS	6–11 years	385	Blood: Hb, ferritin and red blood cell count	11.4% anaemic 5.6% iron deficient 0.4% ID anaemia	Low
Le Nguyen et al. 2013 (9)	Cross-sectional SEANUTS	0.2–11.9 years	2,872	Weight, height, MUAC, waist and hip circumferences Blood: Hb, ferritin, vitamin A and D	14% stunted (< 5 years) 8.6% underweight (< 5 years) 4.4% thin (< 5 years) 15.6% stunted (5-11.9 years) 22.2% underweight (5-11.9 years) ~ 5% of overweight/obese children also stunted 38.65% anaemic (0.5-1.0 years) 18.25% anaemic (2-4.9 years) 12.47% anaemic (5–11 years) 7.75% retinol deficient (6-11.9 years)	Low
Lundeen et al. 2014 (19)	Longitudinal 8 years	1–8 years	1,830	Weight, height and HAZ	1 year: 21% stunted 5 years: 24% stunted 8 years: 19.2% stunted	Low
Tuyet Mai et al. 2003 (38)	Cross-sectional 1999	7–9 years	348 Girls	Weight, height, LMAC, body fat and blood pressure.	27.6% underweight 15.4% stunted 16.6% wasted 5.2% obese	Low
Mai et al. 2020 (44)	Cross-sectional	6–18 years	10,949	Weight, height, BMI-Z and HAZ	19% obese 22% overweight 4% stunted 4% thin	Low
Nguyen et al. 2007a (18)	Repeat cross-sectional 1990–2005 (14 years)	0–5 years	357,396 1990 = 37,972 1994 = 37,654 2000 = 94,469 2002 = 91,921 2004 = 95,380	Weight, height and BMI	Underweight decreased by 18.4% (from 45–26.6%) Stunting decreased by 25.8% (from 56.5–30.7%) Wasting decreased by 1.7% (from 9.4–7.7%)	Low
Nguyen et al. 2007b (28)	Cross-sectional	0–5 years	1,657	Blood: serum retinol and Hb Retinol deficiency = retinol < 0.70 µmol/L Anaemia: Hb < 110 g/L	12.0% retinol deficient 28.4% anaemic < 6 months old: 35.1% retinol deficient 61.7% anaemic	Low
Nguyen et al. 2014	Cross-sectional	0–5 years	4,029	Weight and height	16.8% stunted 13.2% underweight 4.8% wasting	Medium
Phan et al. 2020 (23)	Cross-sectional 2018	11–14 years	2,788	Weight and height using WHO and IOTF classification	17.4% overweight (WHO) 8.6% obese (WHO) 17.1% overweight (IOTF) 5.4% obese (IOTF)	Medium
Roos et al. 2019 (36)	Review article 2009	ND	ND	WHO classifications for anaemia, retinol and zinc deficiency	15% retinol deficient 29% anaemic 81% zinc deficient	Low
Trang et al. 2012 (21)	Prospective cohort study 2004–2009 (5 years)	11–14 years	585	Weight and height	Overweight/ obesity increased by 7.6% (from 14.2–21.8%)	Low
Tuan et al. 2008 (40)	Repeated cross sectional study 1992–2002 (10 years)	2–17 years	70,331	Weight, height and BMI	Overweight/ obesity increased from 1.4–1.8% (p = 0.07) Underweight increased from 32.1–33.5% (p = 0.11).	Low
Tuyet Mai et al. 2003 (38)	Cross-sectional	7–9 years	348	Weight, height, WAZ, HAZ, WHZ, LMAC and body fat	14.65% underweight 8.33% stunted 8.62% wasted 2.32% obese	Low
Vaktskjold et al. 2010 (89)	Prospective cohort study 2005–2006 (1 year)	0–1 year	237	Weight, HAZ, WLZ, and BMI-Z compared to WHO standards Blood: Hb (n = 189)	79% below median for weight-for-length 18.0% in 5th percentile for length-for-age 9.6% in 5th percentile for weight-for age 9.6% in 5th percentile for weight-for-length 20.3% in 5th percentile for BMI-for age 11.1% anaemic	Low
Van Nhien et al. 2008 (30)	Cross sectional	12–72 months	243	Serum blood: copper, zinc, selenium, magnesium, retinol and Hb	86.9% zinc deficient 55.6% anaemic 11.3% retinol deficient	Low
Van Nhien et al. 2009b (31)	Cross-sectional	11–17 years	245 girls	Weight, height and BMI Blood: Hb and trace element levels	20.7% undernourished 20.4% anaemic 26.5% zinc deficient	Low
Thuc et al. 2019 (37)	Cross-sectional	6–11 years	155	Vitamin D deficiency: 25(OH)D < 50 nmol/L	23.9% vitamin D deficient	Medium
Laillou et al. 2013 (32)	Cross-sectional	0–5 years	532	Weight, height Blood: plasma calcium and vitamin D	21% vitamin D deficient 37% vitamin D insufficient 97% mild calcium deficient	Low
Tuyen et al. 2016 (35)	Review article	0–11 years	ND	Vitamin D deficiency: 25(OH)D < 20 ng/mL Insufficient: 25(OH)D < 30 ng/mL	22.8–58% vitamin D deficient 37.5–86.6% vitamin D insufficient	Medium
Poh et al. 2016 (34)	Randomised, cross-sectional survey SEANUTS	2–15 years	2,016	Blood: serum vitamin D	11.1% vitamin D deficient 37.1% vitamin D insufficient 29.4% inadequate vitamin D	Low

BMI; body mass index, BMI-Z; body mass index for-age-Z score, HAZ; height-for-age-Z score, Hb; haemoglobin, IOTF; international obesity task force, LAZ; length-for-age-Z score, LMAC; left mid arm circumference, MUAC; mid upper arm circumference, ND; no data, WAZ; Weight-for-age-Z score, WHO; world health organization, WHZ; weight-for-height-Z score, WLZ; weight-for-length-Z score, 25(OH)D; 25-hydroxy vitamin D.

Table 3

Findings on the determinants associated with different forms of malnutrition in Vietnamese children aged 0–18 years old
Authors and year	Study duration & design	Sample age	Sample size	Measurements	Key findings – risk factors / determinants	Risk of bias
Le and Dinh 2022 (25)	Cross-sectional, two-stage cluster random sampling	6–11 years	782	Questionnaire, weight, height, and BMI-Z	Significant positive association between male and childhood obesity (OR = 2.48, p < 0.0001). Positive association between overweight/ obesity and children who live with only their father (OR = 11.96, p = 0.0219), transport to school being inactive (motorbike/car/bus) (OR = 1.58, p = 0.0096) and mother’s occupation being white collar (OR = 1.56, p = 0.004).	Low
Hong et al. 2007 (39)	Repeated cross-sectional 2002-2004	11–16 years	3,687	Weight, height and BMI	Positive association between increase in overweight/ obesity and male: 113% increase (p < 0.001) Significant difference in the increase in prevalence by gender: obesity and overweight in males increased by 113%, with only a 39% increase in girls. Poorer households showed smaller increase in obesity/overweight at 33%, compared to wealthier households at 77–124%.	Low
Nguyen et al. 2012 (58)	Longitudinal study 2004-2009 (5 years)	11–14 years	759	Weight, height, BMI, questionnaire: level of physical activity and socio-economic status	Levels of ‘moderate-to-vigorous physical activity’ are negatively associated with overweight/ obesity (RR = 0.60, CI = 0.53–0.67).	Low
Trang et al. 2009 (57)	Cross-sectional	11–16 years	2,684	Weight, height, questionnaire: physical activity levels, and family characteristics	Being overweight is positively associated with physical inactivity (OR = 2.5, CI = 1.9–3.2), passive transport to school (OR = 4.2, CI = 3.3–5.2), no recess exercise (OR = 1.3, CI = 1.1–5.6), time spent playing video games (OR = 2.3, CI = 1.7–3.1), or watching television (OR = 1.5, CI = 1.2–1.9).	Low
Huynh et al. 2011 (66)	Cohort study 2005-2006	4–5 years	526	Weight, height, SSF: SSFT, TSFT and suprailia. Questionnaire: physical activity level.	BMI and SSF were negatively associated with neighbourhood safety for boys (β= -0.80, CI= − 1.53 to − 0.08) and girls (β= -0.59, CI= -1.16 to -0.01). Boys increasing BMI was positively associated with both parents being overweight (β = 1.18, CI = 0.21–2.16). Availability of food at home was associated with increased BMI in girls (β = 1.23, CI = 1.91 − 0.55) but not boys.	Medium
Tang et al. 2020 (59)	Cross-sectional	10–15 years	2,660	Weight, height and BMI. SSF: SSFT and TSFT	Overweight status was positively associated with boys (p < 0.0001) TSFT & SSSF significantly higher in girls than boys (p < 0.0001).	Low
Nguyen et al. 2021 (60)	Cross-sectional	11–15 years	2,660	Weight, height and consumption of sugar-sweetened beverages (SSBs)	Negative association between overweight/ obese status and consumption of milk based SSBs. Every kcal more of fresh milk with sugar & condensed milk, can reduce the obesity odds of 0.005 (CI = 0.002–0.008).	Low
Tang and Dibley 2021 (61)	Longitudinal	10–15 years	482	Weight, height and BMI SSF: SSFT and TSFT	Male at higher risk for higher BMI than girls (p = 0.006). Inactive adolescents at higher risk of gaining weight than active adolescents; TSFT (RR = 1.43, CI = 1.22–1.67), SSFT (1.09, CI = 1.00-1.18) and BMI (1.06, CI = 1.02–1.10).	Low
Kim et al. 2022 (24)	Cross-sectional	3–4 years	103	Weight, height, physical activity and sedentary behaviour	Children not meeting screen time guidelines were at a higher risk of being overweight/ obese but was not significant (OR = 0.94, p = 0.904).	Low
Le Nguyen et al. 2013 (9)	SEANUTS multi-stage cluster-randomised sampling	0.2–11.9 years	2,872	Weight, height, mid-upper arm circumference, waist and hip circumferences Blood: Hb, serum ferritin, vitamin A and D	Positive association between undernutrition and rural habitation (p < 0.05). Positive association between overnutrition and urban habitation (p < 0.05). Ferritin: significantly higher levels in urban girls than urban boys (p < 0.05) and significantly higher levels in urban children than rural children (p < 0.05) aged 6-11.9 years.	Low
Tang et al. 2007 (64)	Cross-sectional	11–16 years	1,504	Weight, height and BMI-Z	Being male is positively associated with being underweight (p = 0.001). Non-significant association between being male and being overweight or obese (p = 0.074). Positive association between living in wealthy urban districts and being overweight/ obese (p < 0.001).	Low
Van Lierop et al. 2008 (65)	Cross-sectional	6–10 years	2,631	Weight, height and waist circumference	21.4% were stunted, and higher prevalence was found in rural regions (23.8% vs 17.3%, p < 0.001) Living in urban areas is positively associated with being overweight (4.6% vs 1.6%, p < 0.001).	Low
Tran et al. 2017 (67)	Cross-sectional	12–17 years	1,851	Weight, height and memory tests	No significant association between child maltreatment and overweight or underweight status. Underweight status is negatively correlated with working memory (r= -0.07, p < 0.01) and academic performance (r= -0.08, p < 0.01). Overweight status is positively associated with male (OR = 1.39, p = 0.00) and negatively associated with rurality OR = 0.66, p = 0.04).	Low
Mai et al. 2020 (44)	Cross-sectional	6–18 years	10,949	Weight and height	Positive association between overweight status, urban living (p < 0.001), and male (p < 0.001). Positive association between underweight status and rural living (p < 0.001).	Low
Lavin et al. 2017 (51)	Longitudinal cohort study 8 years	0-8.5 years	1,812	Weight, height and HAZ	Positive associations with moderate/severe stunting were found in low birth weight (OR = 0.114, p = 0.001), food shortages (OR = 0.048, p < 0.001), rural location (OR = 0.068, p < 0.001), decreasing wealth (OR = 0.080, p = 0.008) and ethnic minority (OR = 0.077, p < 0.001).	Low
Mai et al. 2003 (63)	Cross-sectional 1999	7–9 years	348 girls	Weight, height, WAZ, HAZ, WHZ and LMAC	Positive association between rural living and being underweight (OR = 4.5, p < 0.001), stunted (OR = 7.9, P < 0.001), wasted (OR = 2.4, p = 0.039) or undernourished (OR = 3.0, p = 0.045).	Low
Dearden et al. 2017 (50)	Longitudinal	1–8 years	1,905	Height, weight and BMI-Z	Improved access to water at 1 year old was negatively associated with stunting at 1 (RR = 0.27–1.20), 5 (RR = 0.25–1.17) and 8 (RR = 0.25–1.42) years old.	Low
Nguyen 2020 (52)	Cross-sectional	0–15 years	158,019	Height, weight, HAZ and WAZ	Preschool attendance is negatively associated with prevalence of underweight (p = 0.079) and stunting (p = 0.079) at 2–15 years.	Medium
Nguyen et al. 2007a (18)	Repeat cross-sectional 1990-2005 (14 years)	0–5 years	357,396	Weight, height and BMI	Higher prevalence of underweight, stunting and wasting in rural and mountainous areas than urban areas. Larger rates of reduction of underweight, stunting and wasting in urban areas, than rural and mountainous areas. Household size and being a male are all positively associated with being stunted (β= -0.1543, p = 0.0001).	Low
Tran 2008 (45)	Cross-sectional	0–3 years	547	Height, weight and questionnaire	Positive association between fathers not taking children to a medical facility for immunisation and being underweight or stunted (OR = 1.75, CI = 1.07–2.87).	Low
Hien and Hoa 2009 (11)	Cross-sectional	0–3 years	383	Weight and height	Positive association between being underweight and rural living region (OR = 2.22), minority ethnicity (OR = 1.74), mother’s occupation-housewife (OR = 7.91), household size ≤ 4 (OR = 3.07), underweight mother (OR = 1.95), number of children in the family ≥ 3 (OR = 3.35), low birth weight < 2500 g (OR = 7.99), exclusive breastfeeding duration < 6 months (OR = 4.41) and initiation of breastfeeding after 1 hour (OR = 2.54).	Medium
Huong et al. 2014 (46)	Repeat cross-sectional - seasons	24–59 months	853	Weight, height and BMI	Summertime is positively associated with being underweight (p < 0.05) and stunted (p < 0.05).	Low
Nguyen et al. 2014 (20)	Cross-sectional	0–5 years	4,029	Weight and height Maternal CMD	Maternal CMD was positively associated with underweight children (OR = 1.27, CI = 1.01–1.61). Low birth weight was positively associated with stunting (OR = 3.71, p < 0.001), underweight (OR = 3.96, p < 0.001), and wasting (OR = 3.61, p < 0.001). Poor household wealth was positively associated with underweight (OR = 1.99, p < 0.01).	Low
Bennett et al. 2015 (47)	Young Lives Longitudinal Cohort study 2001-06	1–8 years	1,961	Weight, height, questionnaire and risk of maternal CMD	Maternal CMD is positively associated with stunting at age 1 (ARR = 1.24, CI = 1.03–1.62), age 8 (1.22, CI = 1.03–1.45)	Low
Hanieh et al. 2015 (48)	Prospective longitudinal	6 months	1,046	Length, weight and LAZ	Positive association between infant LAZ scores at 6 months and maternal BMI (coefficient 0.04 kg/m², CI = 0.01–0.07), weight gain during pregnancy (0.04/kg, CI = 0.01–0.06) and maternal ferritin concentration (− 41.5 g/twofold increase in ferritin, CI = − 78 to − 5.0). Inverse association between maternal 25-(OH)D concentration and infant LAZ scores (coefficient − 0.06 per 20 nmol/L, CI= -0.11 to -0.01). No association between maternal iodine status & infant LAZ.	Low
Krishna et al. 2015 (49)	Longitudinal	6 months − 15 years	2,489	Weight, height and HAZ	Wealth index is positively associated with growth in children.	Low
Chen 2021 (53)	Young Lives Study Longitudinal 2002–2006 (4 years)	1–6 years	2,000	Weight, height, WAZ, HAZ and WHZ	Negative association between malnutrition and family size; having one additional child is associated with declines of the first child’s HAZ (0.49 SD) and WAZ (0.57 SD).	Medium
Nguyen et al. 2021b (54)	Cross-sectional, follow up	6–7 years	1,579	Weight, height and BMI Maternal weight, height and BMI	Preconception maternal nutritional status is positively associated with child attained size at age 6–7. Child HAZ was positively associated with maternal height (+ 0.28 SD) and BMI (+ 0.13 SD), and faster linear growth at age 6–25 months (β = 0.39–0.42).	Low
Trinh et al. 2021 (55)	Longitudinal	5 months – 13 years	2,000	Rainfall data (flooding, drought), weight, height, BMI, HAZ and WAZ	Positive association between flooding and being stunted (RR = 0.122, p < 0.01) and underweight (RR = 0.067 p < 0.01). Positive association between droughts and stunting (RR = 0.127, p < 0.01). Rainfall shocks can impact parental mental health, increasing the probability of child being underweight by 0.976 (p < 0.001).	Medium
Le Hung et al. 2005 (68)	Longitudinal 1997–2000 (3 years)	0–17 years	2,767	Blood: Hb and ferritin Malaria and intestinal helminth infection (worms)	Malaria is significantly positively associated with anaemia (OR = 2.408, p = 0.0006). No significant association between intestinal helminth & anaemia.	Medium
Van Nhien et al. 2009a (71)	Cross-sectional	11–17 years	245 girls	Weight and height Blood: serum Hb and selenium	Anaemia is positively associated with selenium deficiency (OR = 5.36, CI = 2.57–11.18), being underweight (2.72, CI = 1.37–5.37) and years of age (1.35, CI = 1.14–1.59) in girls.	Low
Hoang et al. 2019 (70)	Cross-sectional	6–9 years	839	Weight and height Blood: Hb and mean corpuscular volume	Underweight, stunting and wasting were all positively associated with anaemia (p < 0.004), specifically normocytic anaemia (p < 0.006). No significant association between anaemia and demographic indicators or socio-economic indicators.	Low
Hall et al. 2001 (26)	Cross-sectional	7–11 years	588	Blood: Hb levels	Anaemia is positively associated with boys: Aged 7–11 years (RR = 1:07, CI = 1.10–1.13) Aged 12–14 years (1.18, CI = 1.12–1.24) Aged ≥ 15 years (1.30, CI = 1.16–1.46).	Medium
Vaktskjold et al. 2010 (89)	Prospective cohort 2005-2006 (1 year)	0–1 year	237	Weight, height, LAZ, WHZ, and BMI-Z	Lower LAZ (β= -2.2, CI= -4.0 to -0.5) and WAZ (-0.5, CI= -1.0 to -0.1) were statistically associated with living rurally.	Low

BMI; body mass index, BMI-Z; body mass index for-age-Z score, CI; confidence interval, CMD; common mental disorder, HAZ; height-for-age-Z score, Hb; haemoglobin, MUAC; mid upper arm circumference, LAZ; length-for-age-Z score, LMAC; left mid arm circumference, OR; odds ratio, RR; relative risk, SSF; skinfold thickness, SSSF; subscapular skinfold thickness, TSFT; tricep skinfold thickness, WAZ; weight-for-age-Z score, WHZ; weight-for-height-Z score.

Table 4

Findings on the interventions and its impacts on addressing different forms of malnutrition in Vietnamese children aged 0–18 years old
Authors and year	Study design & duration	Sample age	Sample size	Inclusion criteria	Intervention group Control group	Measurements	Key findings – results and effectiveness	Risk of bias
Nutrition Sensitive Interventions
Hop and Khan 2002 (3)	Follow-up of national nutrition strategy 1995–2000	0–5 years	National	Child living in included area	National Plan of Action for Nutrition (NPAN), poverty reduction, infrastructure improvement, financial support, agriculture and aquaculture extension, health care, credit & education.	Weight and height	Stunting decreased from 58–37.3%. Underweight decreased from 51.5–25%.	Medium
Mackintosh et al. 2002 (73)	Follow-up study to assess effectiveness of PANP (1993–1995) after 3 & 4 years (1998–1999)	4–6 years (older) 1–3 years (younger group)	55	Families who previously participated in the PANP study and 1 younger child who had not received any PANP exposure Control group: no previous exposure to PANP	Poverty alleviation and nutrition program (PANP): growth monitoring and promotion, positive deviance inquiry, nutrition education and rehabilitation programme, and revolving loan program. (n = 46 household, 142 children) Control group: no intervention (n = 25 household)	Weight, height and WAZ	After 24 months: severe malnutrition (using WAZ) had reduced from 23–6%. No significant difference in the WAZ between the groups. Intervention group were ‘nutritionally better off’, had better feeding habits and weaning practices.	Medium
Watanabe et al. 2005 (75)	Uncontrolled trial and follow up (2004) 5 years total	Intervention: 4–5 years Follow up: 6.5–8.5 years	313	Living in a commune with a high prevalence of malnutrition, poor socioeconomic conditions, no prior intervention programme, and leaders being interested in the project	Nutrition intervention group: including growth monitoring, nutrition education rehabilitation programme, nutrition-seeking and health-seeking behaviours, feeding children locally available nutritious foods, antenatal care, home gardening, savings & credit programme (n = 172). Nutrition programme (as above) & early childhood development (ECD) group: follow up to the prior intervention. Parental training: care and development. (n = 141)	Height, weight, HAZ, WAZ, WHZ, maternal and household characteristics	No statistically significant differences between intervention groups for anthropometric measures, or levels of stunting, wasting or underweight status. Longitudinal results: significant decrease in stunting prevalence in both the nutrition intervention group (13.4%, p < 0.01) and ECD & nutrition group (16.3%, p < 0.01). Severe stunting was only reduced in the ECD & nutrition group by 7.8% (p < 0.01).	Medium
Pachon et al. 2002 (74)	Longitudinal, RCT 2 years	5–25 months	239	Malnourished children matched with healthy children	Save the Children: positive deviance children interviewed to find key ‘good foods’ & behaviours. This included bimonthly nutrition rehabilitation for 9 months to identify ‘good foods,’ increase food quantity, and promote breastfeeding; and monthly growth monitoring and promotion sessions for 2 years (n = 119). Control group: no intervention (n = 119)	Weight, height, BMI, WAZ, HAZ, WHZ and breastfeeding status	At 12 months, intervention children consumed 20% more food than control group (p < 0.01), and were fed more times a day than the control group (p < 0.01) No statistically significant results for WAZ at 12 months. At months 2–6, for children < 15 months, 44.6% control group were undernourished compared to 68.8% (p < 0.05). However, children > 15 months, the intervention group (45.2%) had more well-nourished children than the control group (29.6%, p < 0.01).	Low
Nutrition specific intervention studies
Wieringa et al. 2007 (82)	Double blinded, RCT 6 months	4–6 months	784	No chronic or severe illness, severe clinical malnutrition, anaemia, congenital anomalies	Supplementations for 7 days/week: Zinc (Zn): 10 mg/day (n = 196) Iron (Fe): 10 mg/day (n = 196) Iron + zinc: 10 mg each/day (n = 196) Control group: unfortified syrup (n = 196)	Weight, height, BMI, WAZ, HAZ, WHZ Hb, SF and serum zinc	The Fe and Fe + Zn groups had significantly higher levels of Hb and SF, and lower prevalence of anaemia, than the Zn and placebo groups (p < 0.0001). Iron supplementation significantly increases Hb levels (p < 0.0001). The Zn and Fe + Zn groups had significantly higher levels of zinc than the placebo and Fe groups (p < 0.0001). After baseline value adjustment, Zn levels were significantly higher in the Zn group compared to the Fe + Zn group (p = 0.02). Zinc supplementation had a negative effect on Hb concentrations, independent of iron supplementation (-2.5 g/L, p < 0.001, p-interaction = 0.25).	Low
Hall et al. 2007 (77)	Cluster randomised trial (CRT), 17 months	6 years	1,080	Children in primary schools who had taken part in a school feeding programme (fortified biscuits & milk)	Intervention group: fortified biscuits and milk, total 300kcal. Once a day, 5 times a week. Deworming. Nutrition and hygiene information (n = 360) Control group: no intervention (n = 720)	Weight, height, BMI, WHZ, WAZ and HAZ	The intervention group gained significantly more weight (3.19 kg vs 2.95 kg, p < 0.001) and height (8.15 cm vs 7.88 cm, p = 0.008) than the control group. After controlling for other limiting factors, the intervention programme was statistically significant for weight gain (p = 0.024), and the most undernourished children at baseline gained the least weight.	Low
Hanieh et al. 2014 (81)	Cluster randomised trial (CRT) & follow up, 1 year	6 months	1,175	Pregnant women	IFA: Iron + folic acid supplement daily (60 mg iron + 0.4 mg folic acid) (n = 395) IFA: Iron + folic acid supplement twice weekly (60 mg iron + 1.5 mg folic acid) (n = 399) MMN: Multiple micronutrient supplement + Iron and folic acid, twice weekly (60 mg iron + 1.5 mg folic acid + 13 other micronutrients) (n = 381)	Birthweight, length, and weight	No difference in birth weight as well as infant LAZ at 6 months of age in the twice weekly IFA group compared to the daily IFA group (MD 20.14, CI = 20.29 − 0.02), nor in the twice weekly MMN group compared to the daily IFA group (MD 20.04, CI = 20.20 − 0.11).	Low
Hanieh et al. 2013 (90)	CRT and follow up 1 year	6 months	Follow up: 891	Pregnant women	IFA: Iron + folic acid supplement daily (n = 395) (60 mg iron + 0.4 mg folic acid) (n = 395) IFA: Iron + folic acid supplement twice weekly (n = 399) (60 mg iron + 1.5 mg folic acid) (n = 399) MMN: Multiple micronutrient supplement + Iron and folic acid, twice weekly (n = 381) (60 mg iron + 1.5 mg folic acid + 13 other micronutrients) (n = 381)	LAZ, head circumference, and HAZ	Follow up: Inverse association between maternal 25-OHD status and infant HAZ at 6 months (OR= -0.09, CI= -0.12 to -0.02)	Low
Hop and Berger 2005 (78)	Double blinded, RCT 6 months	6–12 months	306	Not severely wasted, not born prematurely	DDM: daily multiple micronutrient supplement (15 micronutrients including iron) (n = 76) WMM: weekly multiple micronutrient supplement (15 micronutrients including iron) (n = 77) DI: daily iron supplement (Daily adequate intake) (n = 75) Control group (P): daily placebo (n = 73)	Weight, length, LAZ, WAZ, plasma Hb, ferritin, zinc, riboflavin, retinol, tocopherol, and homocysteine	LAZ and WAZ worsened significantly in all groups, apart from LAZ in the DDM group which was significantly less than in the P and WMM groups (p = 0.001). Hb levels increased significantly more in the DMM group (mean = 16.4 g/L, CI = 12.4–20.4) than the P group (mean = 8.6 g/L, CI = 5.0-12.2). PF levels increased significantly more in the DMM and DI groups than the P and WMM groups.	Low
Huy et al. 2009 (79)	Non-random, non-controlled pragmatic trial 2 years	0–2 years	586	Pregnant women	1: Iron (60 mg) + folic acid supplement (400 µg) (n = 211) 2: Multiple-micronutrient supplement (n = 203) 3: Gender training – maternal care from the family and community during pregnancy, and multiple-micronutrient supplement (n = 172) All: nutrition education- encouraging more frequent eating during pregnancy	Baby birth weight (LBW < 2500 g) At 2 years: weight and height	Average birth weight was higher in the two groups receiving multiple-micronutrient supplements than the group receiving iron = folic acid (2: +166 g 3: +105 g) than those receiving iron + folic acid (p < 0.05). LBW prevalence was lower in groups 2 & 3 than in group 1 (4.0%, 5.8% and 10.6% respectively, p < 0.05). At 2 years: children were taller in groups 2 & 3 than group 1 (p < 0.05) and stunting rates were ~ 10% lower (p < 0.05). No statistical significance for weight indicators.	Medium
Le Huong et al. 2007 (83)	RCT 6 months	6–8 years	425	Anaemic children	Iron fortified noodles, 10.7 mg/day (n = 86) Iron fortified noodles (10.7 mg/day) + mebendazole (n = 79) Mebendazole (deworming drug) (n = 79) Iron tablet (dose not reported) + mebendazole (n = 83) Control group: Placebo (n = 82)	Iron status: Hb, SF, sTfR, and haemoglobinopathies analysis. Inflammation: C-reactive protein. Parasite infection status and immunoglobulin E (IgE).	Hb concentration improved, and anaemia prevalence reduced in all groups (p < 0.001). Iron fortification significantly increased levels of Hb, SF and body iron (p = 0.037, p < 0.001 and p < 0.01, respectively), compared to just deworming and the placebo. Deworming showed no increased effect on Hb, iron status or IgE level compared to iron fortification	Low
Thi Le et al. 2006 (91)	RCT 6 months	6–8 years	425	Anaemic children	Iron fortified noodles, 10.7 mg/day (n = 86) Iron fortified noodles (10.7 mg/day) + mebendazole (n = 79) Mebendazole (deworming drug) (n = 79) Iron tablet (dose not reported) + mebendazole (n = 83) Control group: Placebo (n = 82)	Hb, SF, sTfR, and haemoglobinopathies analysis, CRP, parasite infection status, and immunoglobulin E (IgE).	Iron supplementation was more efficient than fortification to treat anaemia for all iron markers: Supplementation (Hb 6.19 g/L, p = 0.001; SF 117.3 µg/L, p = 0.001; and body iron 4.37 mg/kg, p = 0.001) compared to fortification (Hb 2.59 g/L, p = 0.07; SF 23.5 µg/L, p = 0.006; and body iron 1.37 mg/kg, p = 0.001)	Low
Ninh et al. 1996 (86)	Double blinded, RCT 5 months	4–36 months	146	Growth-retarded children, paired to healthy children	Zinc supplementation (10 mg) daily (n = 73) Control group: Placebo (n = 73)	Weight, height, WAZ, HAZ plasma circulating insulin-like growth factor (IGF-I)	Zinc supplementation increased weight by 0.5 kg (± 0.1 kg, p < 0.001) and height by 1.5cm (± 0.2 cm, p < 0.001).	Low
Pham et al. 2010 (92)	RCT 6-month intervention 18-month follow-up	5 months	426	Singleton, breastfed infants Severe anaemia (Hb < 70 g/L).	FF: instant fortified flour, daily for 6 months containing 11 vitamins & 12 minerals (n = 157) FC: complementary fortified food, daily for 6 months containing 11 vitamins & 12 minerals (n = 135) Control group (C group): no intervention (n = 134)	Micronutrient status: Hb, PF sTfR, zinc, and retinol.	Iron deficiency and iron deficiency anaemia were lower in the FF (13.4% and 6.7%) and FC (15.2% and 3.8%) groups compared to the C group (57.5 and 37.5%, p < 0.0001)	Low
Phu et al. 2012 (93)	RCT 6-month intervention 18-month follow-up	5 months	377	Severe anaemia (Hb < 70 g/L).	FF: instant fortified flour, daily for 6 months containing 11 vitamins & 12 minerals (n = 135) FC: complementary fortified food, daily for 6 months containing 11 vitamins & 12 minerals (n = 114) Control group: no intervention (n = 128)	Micronutrient status: Hb, PF, sTfR, zinc, and retinol	Retinol & zinc concentrations didn’t differ significantly among groups. Zinc deficiency was significantly lower in the FF group (36.1%) than C group (52.9%, p = 0.04).	Low
Thach et al. 2015 (80)	Cluster randomised trial (CRT) 9-month intervention 25-month follow-up	6 months	426	Pregnant women	Daily iron-folic acid (IFA) (60 mg elemental iron and 0.4 mg folic acid) (n = 34 communes) Twice weekly IFA (60 mg elemental iron and 1.5 mg folic acid) (n = 35 communes) Twice weekly multiple-micronutrient, iron and folic acid (60 mg elemental iron, 1.5 mg folic acid and MMN) (n = 35 communes)	Weight, length, LAZ and WAZ	The OR of anaemia was significantly lower among infants in the daily IFA (OR = 0.31, CI = 0.22–0.43), weekly IFA (0.38, CI = 0.26–0.54) and MMN (0.33, CI = 0.23–0.48) compared to groups in the observational study.	Low
Berger et al. 2006 (94)	Double blinded, RCT 6 months	4–7 months	915	Breastfed infants aged 4–7 months who free from chronic/ acute illness, severe malnutrition, or congenital abnormalities.	Fe-group: daily dose of 10 mg of iron as ferrous sulfate (n = 201) Zn-group: daily dose of 10 mg zinc as zinc sulfate (n = 195) Fe–Zn group: a daily dose of 10 mg iron þ 10 mg zinc (n = 190) Control group: Placebo: a dose of 100 000 IU of vitamin A was given to all infants to avoid VAD. (n = 198)	Stunting HAZ< -2 z-scores; wasting WHZ< -2 z-scores; underweight HAZ <-2 z-scores; anaemia = Hb < 110 g/l; low Fe stores = SF < 12 mg/l; low Zinc = Zinc < 9.9 mmol/l; IDA = simultaneous low SF and anaemia	Hb and SF levels significantly increased in both Fe and Fe + Zn groups (22.6 and 20.6 g/l for Hb; 36.0 and 24.8 mg/l for SF, respectively) compared to Zn and placebo groups (Hb: 6.4 and 9.8 g/l; SF: 18.2 and 16.9 mg/l, p < 0.0001). Zn increased more in Zn group (10.3 mmol/l) than in Fe + Zn group (8.0 mmol/l, p < 0.03), and Fe and placebo groups (1.6 and 1.2 mmol/l, p < 0.0001). Adding iron to zinc supplements negates the positive effect that sole zinc supplementation had on weight gain (WAZ) (p = 0.0004) and serum zinc (p = 0.02) showing a significant interaction between zinc and iron co-supplementation	Low
Vuong et al. 2002 (88)	Controlled trial 30 days	31–70 months	185	Children with low Hb concentration (100–120 g/L)	Vitamin A supplementation: using Momordica coincidences (gac) fruit (locally available) 1: fruit & rice = 3.5 mg β-carotene (n = 62) 2: powder & rice = 5.0 mg synthetic β-carotene (n = 60) 3: Plain rice, no fortification (n = 63)	Weight, height, HAZ, WAZ and plasma β-carotene and Hb concentration	β-carotene concentrations significantly higher in groups 1 & 2 than group 3 (p < 0.0001). Plasma retinol concentration significantly higher in group 1 (p = 0.0053) than group 2 and (p = 0.0053) group 3. Plasma retinol concentrations were significantly higher in group 1 than group 2 (p = 0.0053) and group 3 (p = 0.006) Hb concentrations increased in all 3 groups. In anaemic children, Hb levels were significantly lower in group 3 than group 1 (p = 0.017), but not than group 2.	Medium
Xuan et al. 2013 (76)	RCT 5 months	18–36 months	334	Not breastfed, no congenital or chronic diseases, and not consuming prebiotics or probiotics.	Intervention group: GAU 1 + milk-isocaloric and isoprotic gum, containing synbiotics, and fortified with vitamins A, C and E, and minerals zinc and selenium, and docosahexaenoic acid (n = 150) Control group: Fortified gum of sufficient protein, carbohydrates, fats, vitamins, and minerals (n = 184)	Height and weight gain, anaemia, zinc, and vitamin A deficiencies	The growth parameters of the intervention group increased significantly more than the control group: Weight (+ 0.43, p < 0.01) Height (+ 1 cm, p < 0.01) and BMI Z-score (+ 0.015, p < 0.05). MNDs were reduced in both the intervention and control groups, more in the intervention groups, but non-statistically significant, anaemia by 14.9% (p = 0.63), vitamin A by 9.5% (p = 0.05) and zinc by 13.6% (p = 0.44)	Low
Nguyen et al. 2021 (87)	Uncontrolled trial, 6 months	6–14 years	151	Children from 5 schools in Can Tho with Vitamin D deficiency/ insufficiency/ low BMD	6–9 years: daily 600 mg elemental calcium & 400 IU vitamin D3 10–14 years: daily 1350 mg elemental calcium & 460 IU vitamin D3	BMD, bone turnover markers, vitamin D level, and PTH	Vitamin D concentration significantly improved (p < 0.001). Prevalence of low BMD significantly reduced by 56.29% (p < 0.05)	Low
Smuts et al. 2005 (2)	Double blinded, RCT 6 months	6–11 months	1,134	Residents in study location, not born prematurely or low birth weight, not severely wasted nor severely anaemic, no fever	WMM: weekly multiple micronutrient supplements (n = 283) DMM: daily multiple micronutrient supplement (n = 280) DI: daily iron supplement (n = 288) Control group (P): placebo (n = 283)	CRP, Pb, retinol, Hb, and riboflavin level	The DMM group had a significantly greater weight gain, growing at an average rate of 207 g/mo compared with 192 g/mo for the WMM group, and 186 g/mo for the DI and P groups. DMM had significantly greater reduction in anaemia (-44% vs -35.1% and − 29.9%), ID (-17.6% vs -13.7% and 9.3%) and VAD (-10.7% vs -4.3% and − 11.4%) compared to DI and P groups (p < 0.05).

BMD; bone mineral density, BMI; body mass index, BMI-Z; body mass index for-age-Z score, CRP; C-reactive protein, HAZ; height-for-age-Z score, Hb; haemoglobin, IDA; iron deficiency anaemia, LAZ; length-for-age-Z score, LBW; low birth weight, MMN; multi-micronutrient, WAZ; weight-for-age-Z score, WHZ; weight-for-height-Z score, PF; plasma ferritin, PTH; parathyroid hormone, RCT; randomised controlled trial, SF; serum ferritin, sTfR; serum transferrin receptors.

Prevalence of different forms of malnutrition in Vietnamese children

The prevalence of malnutrition has changed over time in Vietnamese children, with the prevalence of underweight in children aged < 5 years old decreased by 18%, stunting by 25% ,and wasting by 1.7% from 1990 to 2005 (18). The decreasing trend in undernutrition shown over time aligns with the country’s poverty alleviation plan. The Vietnamese government has launched the Hunger Eradication and Poverty Reduction programme (HEPR) in 1992, which resulted in improved infrastructure in poor communities, greater financial support for ethnic poor families, and employed people to grow the agriculture and aquaculture industries. Later on, in 1995 the National Plan of Action for Nutrition (NPAN) indicated the government’s serious commitment to reducing malnutrition in the country (3). These national programmes have shown positive outcomes on poverty reduction, which were demonstrated by different development indices such as the percentage of poor households decreasing from 41% to just 5% from 1985 to 2005 (3). Since 2005, poverty has continued to reduce. A report highlighted further reductions in poverty, to 9.8% in 2016, with an even larger decline for ethnic minorities (13%) (95).

Although Vietnam has managed to significantly reduce MNDs and undernutrition during the past decades, this decline is now slowing down and there is a rise in overweight and obese children. The slowing decline potentially stems from the initial decline of malnutrition being simpler cases to treat through the national nutrition programme, and more complex cases can be difficult to treat due to multifactorial causes. This finding was in line with the findings generated from the data obtained from UNICEF/WHO/World Bank Group (96) illustrated in Fig. 3, where a steady decline in wasting (11.9–5.2%), stunting (41.2–22.4%) and underweight (35.8–12.2%) from 1998 to 2019, and a slow increase in overweight (1.4–7.4%) have been observed in children aged < 5 years old. It is important to note that, for the first time in 2017, the percentage of overweight children aged < 5 years old overtook the percentage of wasted children in Vietnam.

However, the prevalence of overweight varied across different studies, this may depends on the age of participants, location and the year in which the studies were taken place, measurements taken, and definitions of under and overnutrition. Overall, the prevalence of overweight and obesity increased as age increased. A large cross-sectional study reported that 22% and 19% of the Vietnamese children aged 6–18 years old in the urban regions of Ho Chi Minh City, were found to be overweight and obese, respectively in 2020 (44). Whereas in Hanoi, obesity was slightly reduced (-2%) although the prevalence of overweight increased from 9.1% in 2013 to 16.7% in 2016 (22). The estimate of the prevalence of overweight and obesity differed when different definitions were applied e.g. WHO vs IOTF. A study reported that the prevalence of obesity was higher when the IOTF definition (Asian population) was applied, with 31.0%, 16.0% and 10.1% of the primary, secondary and high school children were obese, compared to WHO definition (26.9%, 16.1% and 5.2%), respectively (44).

Prevalence of micronutrient deficiencies

Khan et al. 2008 reported a higher prevalence of anaemia in children (56%) (30) compared to Nguyen et al. 2007 (28%) (28). Both studies applied the same cut-off for Hb to define anaemia (Hb: <110 g/L). The variation could be due to the regional difference as the children in Khan et al. 2008 (30) were recruited from rural areas, whereas Nguyen et al. 2007 (28) were conducted in both rural and urban areas. A higher prevalence of anaemia occurring in rural areas may be due to the high incidence of intestinal parasitic infections, which are very common in Northern, rural Vietnam (97), alongside poorer quality health care and poorer economic status compared to the urban areas. Whereas a lower prevalence of anaemia was observed in older aged children (13%) (26), and this may be due to greater impacts of maternal iron status on child’s iron status after birth, but less so as the child ages (98).

Vitamin D deficiency varied across studies, from 11.1% in 2–15 year olds (34) to 23.9% in 6–11 years old (37). Another review article found a larger range, from 23–58% (35). These results indicate that the prevalence of vitamin D deficiency might be higher in older children. Limited data on the prevalence of zinc deficiency does not allow for much detailed discussion. Nonetheless, a review article reported that the prevalence of zinc deficiency varied from 22.5% in infants aged 6–11 months (2) to 91% in older aged children (36).

Determinants

As reported in Table 3, the most common determinants for undernutrition were living in rural areas, having LBW, and having parental CMD. For overnutrition, an increased risk was found in children living in urban areas, being a boy, and having an inactive lifestyle. The determinants of MNDs were understudied, and based on the limited data, the risk of anaemia was greater in individuals with malaria, selenium deficiency, being underweight, and increasing age.

Determinants of childhood overweight and obesity

Children living in urban areas spent significantly more time indoors compared to children living rurally, and were more likely to be overweight and obese (9). Besides, in urban regions, there are fewer open spaces, playgrounds, and neighbourhoods that are safe for walking and outdoor activities, alone (7). Huynh and Dibley reported that as neighbourhood safety increased, BMI and the sum of skinfold thickness (SSF) decreased (66), this may be due to the parents’ perception of neighbourhood safety for physical activity, meaning they are more likely to let their children spend time on outdoor activities. One of the possible explanations for boys being at a higher risk of obesity than girls (25), especially in urban areas, is that boys spent more time doing sedentary activities, including increased screen time such as watching TV or electronic devices.

Other reasons could be due to male chauvinism, where parents regard boys as more valuable than girls (99), resulting in parents overindulging their sons more than their daughters through gifts or food. Inactivity was linked to an increased risk of being overweight or obese in multiple ways, through low physical activity levels, inactive transport methods to school (bus, car, motorbike), or no recess activity (25, 57, 58). This association is well established, as doing exercise, and living a more active lifestyle plays an important role in controlling excess body weight (100). Previous study demonstrated an association between loneliness, sedentary behaviour, and being overweight or obese. It is believed that prolonged sedentary behaviour may contribute to loneliness due to the time spent alone, compared to peer involvement in physical activity, especially at school and sports clubs (62).

Le and Dinh 2022 reported that children living with their father only, compared to those with both their mother and father, had an 11.96 times higher risk of being obese or overweight (25). A possible explanation for this increased risk could be due to fathers being less likely to limit food access and monitor children’s food intake (101). However, due to the low divorce rate in Vietnam, this only represents 1.15% of the population and hence, to properly establish an association between these two variables, a larger sample size of this population would be required. Huynh et al. 2011 reported that increasing BMI was found in children with overweight parents, however, such association was only significant in boys and not in girls (66). This is a complex mechanism, it is thought to be due to children picking up their parents’ unhealthy eating habits and dietary patterns (102).

According to the ‘nutrition transition theory’ proposed by Popkin 1994 (103), rapid urbanisation and economic development, have contributed to the nutrition transition in Vietnam, from traditional Vietnamese diets, which are rich in fresh fruits and vegetables and rice, to diets that are high in processed foods, refined grains, meat, dairy products, saturated fats, sugars and low in fibre (104, 105), which resulted in an increased risk of overweight and obesity. Overweight and obesity were shown to be more prevalent in wealthy areas, especially wealthier urban areas (64). One plausible reason for this is that children are more likely to expose to aggressive advertisements from international fast-food companies, which encourages higher consumption of unhealthier or energy-dense foods in children (7). Moreover, urban food environments generally have more small food stores, convenience stores, and fast-food outlets than large supermarkets (106). The presence of supermarkets is significantly associated with lower rate of obesity in America. Multiple studies have found that the presence of convenience stores was associated with unhealthy eating behaviours in children (107) and higher body weight in other populations, such as American adults (108) and adolescents (109). The association between convenience stores and the eating behaviour of children was insignificant in South Asia, however, no data has been reported in Vietnam.

In terms of wealth, overnutrition is likely due to a larger budget being available for food shopping and more foods being available in wealthier household. This is in contrary to the case in western countries, where lower SES status are more likely to link with overweight and obesity. In addition, wealthier families tend to be busier due to having white-collar jobs, a previous study reported an increased risk of overweight and obesity by 1.56 times in children with white collar mothers (25), and being busier may link to higher consumption of convenience foods. An alternative perspective is that growing up in a wealthier household isn’t solely a predictor of being overweight or obese. Other factors such as lack of physical activities and more available of computers resulting longer screen time may co-exist alongside the improvement of household income. Indeed, another study reported that household wealth could promote healthier physical growth through higher HAZ and lower risk of stunting (49). Healthier growth could be due to socioeconomic reasons, for example, increase in food availability, improved access to health services and hygienic water. Access to health services and safe water reduces the risk of health problems and infections that can consequently cause malnutrition alongside with poor diet and nutrition.

Determinants of childhood underweight, stunting and wasting

The most reported determinants for childhood undernutrition in Vietnam include living in rural areas. Families living in rural areas generally have lower economic status than those in urban areas, and many rural inhabitants’ livelihoods depend on the agricultural industry. The income generated from agricultural activities varies widely due to the price fluctuation of produces and climate change (110). Other contributing factors include poor diet quality and higher levels of physical activity (44). Moreover, undernutrition was more prevalent in ethnic groups, and this is potentially due to the ethnic minorities were more likely to be associated with poorer economic status, living in rural/mountainous areas, and less likely to be benefitted from the economic growth in the 1990s (111). Individuals with a poorer economic status mean that they are more likely to live in a poor quality of housing, with limited sanitation and water access, food access, employment support and health care. The associations between food shortages and undernutrition are self-explanatory as reduced food availability means inadequate energy and nutrient intake in individuals, resulting in an increased risk of childhood undernutrition (51).

Previous study showed that improved sanitation can reduce exposure to diarrhoeal diseases (50), which can, in turn, reduce the risk of undernutrition (112). Household size was found to be positively associated with undernutrition in three studies (11, 18, 53). Larger household sizes mean there are more mouths to feed and so children may receive lower quantities of food, resulting in inadequate energy and nutrient consumption. This was supported by the findings from Young Lives (53), as the authors reported that having one additional child was associated with a significant decline in the first child’s HAZ and WAZ by 0.57 SD and 0.49 SD, respectively. In addition, preschool attendance was found to be negatively associated with underweight and stunted children aged 2–15 years (52), which is likely due to the high-quality diets (three meals a day) provided in the preschools, which accounted for about 60–70% of the calorie requirement needed for children per day (52).

Children who were born with LBW were associated with a higher risk of being stunted, wasted, and underweight (11, 20). LBW arises from poor maternal nutritional health status during pregnancy, mother’s health during adolescence, and possible premature birth (113). LBW is commonly associated reduced immune system and increased vulnerability to illness. It is no surprise that LBW is associated with under-nutrition. The risk of being underweight was increased by 4.41 times and 2.54 times in children with exclusive breastfeeding duration less than 6 months, and initiation of breastfeeding being longer than 1 hour after birth. Thus, optimal breastfeeding and complementary feeding practices are essential to ensure the children receive an adequate amount of nutrients for optimal growth, to protect against malnutrition, infections, and diseases (114).

Maternal factors such as the mother’s height, BMI, and nutritional status were positively associated with child growth indicators (115, 116). This finding emphasizes the need for pregnant women as well as women of reproductive age to have a healthy weight, or BMI to increase the likelihood of producing healthy children. Parental mental disorders were also positively associated with children being underweight and stunted (20, 47) which can be explained by the parent’s hindered ability to take care of their children, either through illnesses, not seeking health care, or poor hygiene practices, poor prenatal care, and/or poor feeding practices. The feeding practices included poor quality breastfeeding, lacking diet diversity, low meal frequency, and low consumption of iron-rich or iron-fortified foods (20).

Determinants of childhood micronutrient deficiencies

Determinants of MNDs were the least investigated types of malnutrition in Vietnam, with only three studies reporting the determinants of anaemia and vitamin A deficiency being identified. Anaemia was found to be positively associated with malaria, deficiencies in iron, selenium, and retinol, being underweight, and age (68, 71). One of the studies was conducted on an ethnic minority population living in a mountainous area (68), whereas another study was conducted in girls from a rural and poor area, suggesting that the determinants found were not generalizable to the whole Vietnamese child population. Girls, after the start of menstruation, and/or having prolonger menstrual cycles (> 7 days), are more likely to have anaemia (117).

Although iron deficiency is one of the main causes of anaemia but not all anaemia cases can be prevented by iron supplementation. There are other causes for anaemia such as the presence of other nutritional deficiencies, specifically selenium and/or vitamin A (71) may also increase the risk of anaemia. The mechanisms behind this association may be related to inflammation that occurs in selenium-deficient individuals that resulted in the upregulation of an interleukin, which plays a role in iron metabolism through the iron-regulatory hormone hepcidin (71). Vitamin A deficiency also hypothetically triggers anaemia due to the impaired synthesis of Hb (118). Being underweight was also found to be associated with anaemia and iron deficiency, as individuals who are not consuming sufficient energy or diverse diet are likely to also not consume an adequate amount of dietary micronutrients. More research should be completed examining the link between overweight and other MNDs.

Although much effort has been made to control MNDs in Vietnam, prevalence still remains high, especially in mountainous areas (119). However, future investigations are needed to explore the effects of malaria and other non-nutritional factors on anaemia. Overall, the interpretation of the key determinants of MNDs is limited by the scarcity of MNDs data primarily due to the limited laboratory facility and testing capacity.

Intervention and its effectiveness in addressing different forms of malnutrition

The intervention studies included in this review were intervened on different scales in both rural and urban areas, mainly focusing on undernutrition and MNDs.

Nutrition-specific interventions

Of the 14 studies investigating the impacts of nutrition-specific interventions, 50% measured micronutrient biomarkers, 36% measured anthropometric indices, and 14% measured both micronutrient biomarkers and anthropometric indices. 93% of studies demonstrated improvement in at least one outcome measure, either biomarkers or anthropometric indices, and 7% showed no improvement in anthropometric indices but did show improvement in certain biomarkers. The average duration of the interventions was 11.5 months, ranging from 1 month to 25 months.

Most studies investigated the impacts of daily multi-micronutrient supplementation (e.g., 13–15 micronutrients) or fortification foods on children’s nutritional status. The dosage effects of supplements were investigated across different intervention studies, specifically in iron (10–60 mg), and folic acid (0.4–1.5 mg), whereas the dosage of zinc supplements given in the interventions were fairly consistent (10 mg). All supplementation interventions reported improvement in the child’s nutritional status in at least one of the outcomes. Only one study reported a decrease in WAZ and HAZ/LAZ in infants aged 6–12 months of all intervention groups (intervention: daily multiple micronutrients, weekly multiple micronutrients, or daily iron supplements) and placebo groups (78) suggesting malnutrition was not fully reversed. However, the increase in the prevalence of stunting was much smaller in the daily multi-micronutrient supplementation group (74%; from 11–19%) compared to the placebo group (327%; from 5.5–23.3%), with the other treatment groups showing intermediate increases. The authors concluded that even though these differences were not significantly different across the groups, but if the period of supplementation had been continued beyond the first year of age, the impact of the daily multiple micronutrient supplementation on the prevalence of stunting at two years of age, when length–growth faltering ceases, would likely to be significant (78).

Given that MNDs are still prevalent among Vietnamese children, and food fortification is an effective method of treating MNDs, the urge to promote national fortification programmes is therefore essential. Fortification of micronutrients in foods is an important content specified in the Government Decree 09/2006/ND-CP dated 28th January 2016 (Decree 09). The Government Decree 09/2016/ND-CP has mandated the fortification of salt with iodine, wheat flour with iron and zinc, and vegetable oil with vitamin A. Decree 09 is considered one of the effective strategies by the government to promptly overcome shortcomings in the macro policy on food fortification with micronutrients. This is indeed a promising solution with many advantages, applied by many countries, including developed countries. However, the implementation of Decree 09 still faces many difficulties.

It is worth noting that two studies consistently reported negative interaction between zinc and iron co-supplementation on serum zinc levels, WAZ, or anaemia (82, 94). Zinc supplementation alone was more effective at improving zinc deficiency and WAZ, and whereas iron supplementation alone was more effective at reducing anaemia, compared to combined zinc and iron supplementation. The mechanism for this interaction between zinc and iron is likely due to the competitive absorption through a shared, non-specific pathway (120). Taking each supplement 30 minutes apart would be enough to limit their interactions and allow sufficient absorption of each micronutrient.

Nutrition-sensitive interventions

The nutrition sensitive intervention programmes included growth monitoring, nutritional rehabilitation, loan programmes, improved health care and positive deviance inquiry. For the nutrition-sensitive intervention studies, the PANP, which is considered one of the largest scaled national programmes, was found to be the most effective intervention in reducing child malnutrition (3). However, the study did not compare the intervention group to a control group as the intervention was a national scale study, and it would be difficult to find children who were not exposed nor affected by the policy changes of the PANP. Nonetheless, as a national-scale programme, there were significantly more resources compared to the smaller-scale intervention programmes.

The other three nutrition-sensitive programmes are largely similar to each other and the PANP strategy. Positive deviant childcare practices resulted in improvement in anthropometric indices and eating/feeding behaviours when applied to children as well as their younger siblings (73). Similar findings were observed in another study which reported improved feeding practices and an increased in the proportion of well-nourished children when using a similar method as positive deviance (74). Furthermore, Watanabe et al. 2005 reported a decrease in the prevalence of stunting following a nutrition intervention of growth monitoring and nutrition education (75). The education involved educating children and parents about locally available nutritious foods. Each study reported slightly different outcomes and populations so it is difficult to assess the most effective nutrition-sensitive intervention.

Deworming has shown no impact on any biomarker outcomes, whereas iron fortification has shown positive effect on iron levels after 6 months intervention (83). The percentage of students with intestinal worms (Ascaris, Trichuris, or hookworms) at baseline was relatively high, and deworming significantly reduced the levels of intestinal worms in most treatment groups. This finding suggests that intestinal parasitic infections play a significant role in anaemia, thus future supplementation or fortification programmes could be supplemented with deworming to enhance the effectiveness of such programmes in alleviating anaemia, especially in areas where a high rate of infection/inflammation was observed.

National nutrition policy in Vietnam

The National Nutrition Strategy (NNS) 2021–2030, towards 2045 was ratified by the Vietnamese Prime Minister (NNS Decision No. 02/QD-TTg) to assure continued efforts and strong commitment of the government to improving the nutrition situation of the population (121). The NNS 2021–2030 is a key development in recognizing the role of nutrition for improved quality of life, sustainable human and social development. This NNS is a follow-up to the NNS 2011–2020, in which nutrition objectives have been incorporated into the Party’s documents, National Action Plan as well as action plans of related sectors in various levels.

Overall, Vietnam showed great success in reducing malnourished children to a level close to the Millennium Goals (122), but ethnic minority groups are still being left behind, and hence limited the progress on national reductions (123). Thus, this re-emphasises the policy’s needs to identify and focus on the most vulnerable population, especially the ethnic minority groups and address the identified determinants of malnutrition, to achieve a national reduction of malnutrition. Meanwhile, activities such as prevention of overweight, obesity, and diet-related non-communicable diseases, promotion of physical growth, food safety and quality, food security, and ending of poverty have been prioritised by the government and, in turn, being incorporated into the national targeted programmes. The inter-sectoral coordination and social mobilisation have brought about positive results, and many specific action plans for the implementation of the NNS have been formulated by different sectors.

Current evidence gaps and future recommendations

Despite the large amount of data that has been collected and analysed, a gap on this topic remains. There is limited understanding of the determinants of MNDs and identifying such determinants would the development of targeted interventions tailored to address the core contributors of such malnutrition problem to effectively improve children’s nutritional status. No study has been investigating the co-existence or association between MNDs and overweight/ obesity. Research into this issue provides insight on the scope of the problem. Most importantly, no intervention studies were found addressing the issues of overweight and obesity in children, which an obvious gap is given the rapid development in such malnutrition problem.

The provision of nutritional education and the creation a non-obesogenic environment is one of the very important aspects in preventing and tackling childhood overweight and obesity. Joint efforts from local government, schools, parents, and food industries will be required to ensure the availability and accessibility of more affordable and healthier options of commercial food products to make them more appealing to consumers. Moreover, parental feeding practices play an important role in shaping children’s eating habits and hence their growth and weight status. To promote an active lifestyle among the children, schools and teachers could promote and incorporate physical activity as part of the daily school schedule, as well as to encourage more active methods of transport to school such as walking or cycling instead of driving or getting the bus.

Strengths and limitations

The main strength of this review is that it has comprehensively and systematically assessed a large number of studies, effectively gathering information on three key areas of malnutrition research, including the prevalence, key determinants, and potential interventions or strategies to address different forms of malnutrition in Vietnamese children. In addition, the quality of the intervention studies was generally very high with a low risk of bias, with almost all papers being controlled with a placebo treatment and being blinded to at least the participants. High reproducibility is also a strength of this research. The use of the standard PRISMA method for a systematic review and a standardised search strategy means that this review can be reproduced and compared with other reviews following the same format and using the same search strategy.

One of the limitations of this review is the heterogeneous nature of the study outcomes, limiting the possibility to perform a meta-analysis on the extracted data. Another limitation is the use of BMI as a measure for overweight or obese status, as it cannot distinguish between lean mass and fat mass, potentially overestimating the prevalence of obesity (124). The cross-sectional nature of the risk factor studies means that it cannot be determined if the risk factor occurred before, during, or after the emergence of malnutrition. This means that the risk factors identified can only be referred to as associations and not a causal relationship (125). Cohort studies provide a stronger evidence base for causational relationships, but still cannot demonstrate that a risk factor is the single cause of malnutrition.

In conclusion, undernutrition is still affecting one quarter of Vietnamese children aged under 5 despite a significant reduction over the decade. MNDs remain to be a serious problem particularly on anaemia and deficiencies in iron, zinc and vitamin D, whilst overweight and obesity are rapidly rising requiring attention and intervention, indicating the existence of DBM in this region. This finding highlights the needs for double duty actions to simultaneously and effectively address different forms of childhood malnutrition in Vietnam. The most reported risk factors for children being underweight, stunted, or wasting were living in rural areas, being of an ethnic minority, LBW, and children with underweight mothers. Common risk factors for overweight and obesity were having a sedentary lifestyle, living in urban areas, being male, and living with father only.

Most of the nutrition-specific intervention strategies including supplementation and food fortification demonstrated positive outcomes; either through improvements in anthropometric indices, micronutrient biomarkers, or diet-related behaviours. Large-scale, nationwide nutrition-sensitive intervention programmes which collectively address different environmental aspects that affects child’s health and food choices such as food availability, education, health care, and access to water and sanitation are more likely to be effective in promoting optimal child growth in the long term. However, evidence on the potential intervention strategies, especially on MNDs and overnutrition are still limited to inform policy decision, thus future researches are warranted.

BMD; bone mineral density, BMI; body mass index, BMI-Z; body mass index for-age-Z score, CI; confidence interval, CRP; C-reactive protein, HAZ; height-for-age-Z score, Hb; haemoglobin, IDA; iron deficiency anaemia, IOTF; international obesity task force, LAZ; length-for-age-Z score, LBW; low birth weight, LMAC; left mid arm circumference, MMN; multi-micronutrient, MNDs; micronutrient deficiencies, MUAC; mid upper arm circumference, ND; no data, OR; odds ratio, PF; plasma ferritin, PTH; parathyroid hormone, SD; standard deviation, SDGs; sustainable development goals, SF; serum ferritin, SSF; skinfold thickness, SSSF; subscapular skinfold thickness, sTfR; serum transferrin receptors, TSFT; tricep skinfold thickness, WAZ; weight-for-age-Z score, WHO; world health organisation, WHZ; weight-for-height-Z score, WLZ; weight-for-length-Z score, 25(OH)D; 25-hydroxy vitamin D.

Acknowledgements

The authors would like to express their greatest appreciation to Jyotiringana Saha and Xiaojun Wang for their contributions on the development of search strategy and data analysis.

Author’s contribution

CM conducted searches, screening, quality assessment and data extraction, and checked and approved by PYT and CLC; CM, PYT and CLC analysed and interpreted the data; YYG designed and supervised the work; CM wrote the first draft of the manuscript; CM, PYT, CLC, TTN and YYG edited and revised the manuscript; all the authors read and approved the final manuscript.

Funding

This research was funded by UK Biotechnology and Biological Sciences Research Council (BBSRC) (Grant number: BB/T008989/1), with a project title of “Addressing micronutrient deficiencies associated with the double burden of childhood malnutrition in China, a combined food system framework”.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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Prevalence, determinants, intervention strategies and current gaps in addressing childhood malnutrition in Vietnam: a systematic review

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Abstract

Background

Methods

Results

Conclusion

Figures

Introduction

Methodology

Inclusion and exclusion criteria

Search strategy

Study selection

Data extraction

Data synthesis

Quality criteria checklist for risk of bias

Results

Risk of bias assessment

Prevalence of different forms of malnutrition

Study’s characteristics

Summary of the results

Determinant of different forms of malnutrition

Study’s characteristics

Summary of the results

Interventions and its impacts on addressing different forms of malnutrition

Study’s characteristics

Summary of the results

Discussion

Prevalence of different forms of malnutrition in Vietnamese children

Prevalence of micronutrient deficiencies

Determinants

Determinants of childhood overweight and obesity

Determinants of childhood underweight, stunting and wasting

Determinants of childhood micronutrient deficiencies

Intervention and its effectiveness in addressing different forms of malnutrition

Nutrition-specific interventions

Nutrition-sensitive interventions

National nutrition policy in Vietnam

Current evidence gaps and future recommendations

Strengths and limitations

Conclusion

Abbreviations

Declarations

References

Additional Declarations

Supplementary Files

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