Assessment of Diet Quality and Health-Related Quality of Life in Young Adults According to Household Food Security Status and Income Level


 Background

Food insecurity is still a concern not only in low- and middle-income countries but also in high-income countries and it is reported to have a relationship with health outcome such as chronic diseases. This study was conducted to compare diet quality and health-related quality of life in young adults according to their household income and food security.
Methods

Our population-based sample included 10,224 young adults aged 19–34 y participating in the Korea National Health and Nutrition Examination Survey (KNHANES) 2008–2018. The participants were classified into four groups according to household income and food security: food security & higher-income, food insecurity & higher-income, food security & low-income, and food insecurity & low-income. General characteristics, daily diet, and nutritional quality were compared among the four groups.
Results

The percentage of participants consuming daily diet with protein, vitamin A, B1, B2, niacin, vitamin C, calcium, phosphorus, and iron less than Estimated Average Requirement increased in the food insecurity & low-income group. In case of most commonly consumed food, ramen and sprite were highly placed in the food insecurity & low-income group while apple and beef ranked relatively high in the food security & higher-income group. Multiple logistic regression analysis showed that odds ratio (OR) (95% confidence interval, CI) of Euro Quality of Life five Dimensions (EQ5D) in the food insecurity & low-income group were 1.55 (1.05–2.29) and 1.33 (1.07–1.64) for mobility and anxiety/depression respectively, compared to the food security & higher-income group after adjusting confounding factors.
Conclusions

Household food insecurity and low-income had relationships with poor diet quality and poor health-related quality of life in young adults, in particular, mobility and anxiety/depression.

4C, 2013-12EXP-03-5C, 2018-01-03-P-A). KNHANES is a legal survey conducted based on the Koreans National Health Promotion Act and is designed to assess the health-related behaviors, chronic diseases prevalence status, and food nutritional state of Korean people. As KNHANES corresponds to research projects conducted by nation for public welfare according to Article 2-1 of the Bioethics and Safety Act and Article 2-2-1 of Enforcement Regulations of the same Act, it was conducted in 2015 -2017 with IRB review exemption. The survey target was 11,250 adults aged 19 -34 y who participated in the health survey and the dietary intake survey of KNHANES IV-2 to KNHANES VII-3. The exclusion criteria were as follows: persons who had no food security data (n=30), persons who had no health-related quality of life (EQ5D) data (n=359), pregnant women (n=337), persons with a history of cancer (n=43), persons who had no information on household income (n=76), and persons whose daily energy intake was less than 250 kcal or 5000 kcal or higher (n=181). As a result, a total of 10,224 people were included in the analysis.

General Characteristics
Age, sex, body mass index (BMI), marital status, women's birth experience, residential area, monthly household income, household composition type, occupation, education level, smoking status, alcohol consumption, and subjective health state of participants were analyzed. For monthly household income, monthly income was analyzed using gross household income variable of KNHANES and annual income was analyzed after converting it into monthly income by dividing by 12.

Household Food Security and Household Income
Household food security was investigated by a question on household dietary life status. The survey participants selected one from four response options to the question "Which of the following best describes your household dietary life status for the past one year? The participants who responded "Our family could have many different types of foods as much as we wanted" were classi ed as the food security group and the participants who responded "Our family could have su cient amount of food but could not eat various kinds" or "Our family went short of food from time to time due to nancial di culty" or "Our family often went short of food due to nancial di culty" were classi ed as the food insecurity group. As for household income, using household income quartiles, participants in low and low-middle categories were classi ed as the low income group and participants in middle-high and high categories were classi ed as the high income group. The sensitivity and speci city of a single food insu ciency questionnaire with the food security status by 18-item questionnaire were reported as 56.8% and 92.3%, respectively [34].
Euro Quality of Life ve Dimensions (EQ5D) EQ5D was developed by Euro Quality of Life Group and is an index to assess health-related quality of life with ve dimensions [35]. It consists of mobility, selfcare, usual activity, pain/discomfort, and anxiety/depression and three response options were used (not at all, some problems, many problems). EQ5D was investigated with the approval of EuroQol Group (www.euroqol.org), and validity and reliability were assessed in the Korean population-based survey [35]. In this study, the participants who responded their daily life was hindered or they felt uncomfortable with daily life in mobility, self-care, usual activity, and pain/discomfort areas or the participants who responded they had an anxiety or depression in anxiety/depression area were classi ed as the any problem group and the subjects who responded they had no discomfort at all in those areas as the no problem group.

Food intake assessment
The food intakes of the participants were estimated by the 24-h dietary recall method. In the study, the food items were categorized into 18 food groups including cereal and cereal products, potatoes and starch products, sugar and sugar products, beans and bean products, nuts and seeds products, vegetables, mushrooms, fruits, meat and meat products, eggs and egg products, sh and shell sh, seaweeds, milk and dairy products, oil and fat, beverages, seasoning, processed foods, others. Furthermore, we estimated most commonly consumed foods of participants. Among the foods taken by participants, in case the same food ingredients were used even though cooking and processing methods were different, the case was classi ed as one kind of food. Twenty major most commonly consumed foods were selected by food lists with high intake amount.

Nutrient intake assessment
Daily intake of carbohydrates, protein, and fat in participants and energy composition were calculated. Intake of vitamins and minerals (calcium, phosphorus, iron, sodium, potassium, thiamin, ribo avin, niacin, vitamin C, and vitamin A) was assessed. Calcium and vitamin A are especially nutrients that are prone to lack among Koreans [36,37]. Therefore, we evaluated nutrient intake status including these nutrients. In addition, to assess the quality of dietary intake, we investigated the intake status compared to 2020 Dietary Reference Intakes for Koreans [38]. The percentages of participants who took less than Estimated Average Requirement (EAR) by nutrients were calculated. Statistical Analysis SAS 9.4 software (SAS Institute, Cary, NC, USA) was used for statistical process of all data. As for KNHANES, SURVEY procedure was used with strati ed, multistage sampling design, and signi cance was set to α < 0.05 for the test. In this study, participants were classi ed into four study groups based on household food security and in-come: Food security & higher-income, food insecurity & higher-income, food security & low-income, and food insecurity & lowincome groups. And general characteristics, eating habits, food and nutrient intake, and most commonly consumed foods were compared between four groups and a relationship with health-related quality of life was analyzed. General characteristics and eating habit related matters of young adults according to the food security and household income groups were compared and intake of foods and nutrients was estimated.
For categorical variables, the ratio (weighted %) considering frequency and weight was calculated by conducting chi-square test through SURVEY FREQ procedure and for continuous variables, weighted mean and standard error were calculated using SURVEY MEANS procedure and signi cance by groups was tested by conducting analysis of co-variance (ANCOVA) using SURVEY REG procedure. Post hoc analysis was performed using Tukey's test and age and sex were adjusted. SURVEY LOGISTIC analysis was performed to calculate odds ratios (ORs) and 95% con dence intervals (CIs) for health-related quality of life in young adults according to food security and household income. We conducted analyses adjusted for age, sex, BMI, marital status, residential area, occupation, education level, smoking status, and alcohol consumption.

Results
General characteristics of young adults according to household income and food security In the result of comparing demographic characteristics according to household in-come and food security, all variables except for sex had signi cant difference (p < 0.05). In the food security & higher-income group, age, monthly household income, the percentage of married persons, university graduates or higher, and administrators/specialists were higher than other groups. On the contrary, the food insecurity & low-income group showed higher percentage of high school graduates and current smokers than other groups and the percentage of poor and that of very poor were high in case of subjective health state (Table 1). Eating habit of young adults according to household income and food security Eating habits of young adults according to household income and food security were presented in Table 2. Young adults of the food insecurity & low-income group showed higher percentage of skipping breakfast, lunch and dinner than other groups (p < 0.05). Young adults of the food security & higher-income group ate out more frequently than other groups and the percentage of dietary supplement user was signi cantly high (p < 0.05). Values are n (weighted %). 1 Signi cant difference among the study groups were analyzed by χ2 test. 2 Study subjects with dietary supplement used for longer than two weeks during the previous year.
Intake amount of foods and nutrients in young adults according to household income and food security Intake amount by food group in young adults according to household income and food security was presented in Table 3. Total food intake of the food security & high-er-income group was 1,646.8 g, which was higher than food security & low-income and food insecurity & low-income groups, but not food insecurity & higher-income (p < 0.05). In the food insecurity & low-income group, intakes of vegetables and beverages were higher than food security & higherincome group. For fruits, sh/shell sh, and seasoning, the intake of food security & higher-income group was higher compared to food security & low-income and food insecurity & low-income groups but not the food insecurity & higher-income group. Intake of cereal & cereal products and nuts & seeds products in the food insecurity & low-income group was 295.7 g and 5.3 g, respectively, which were signi cantly higher than those in the food security & low-income group. Intake of nuts & seeds in the food insecurity & low-income group was signi cantly higher than that in the food security & low-income group as the former group took in acorn jelly of 1.98 g and acorn powder of 0.01 g, respectively. However, intake of nuts & seeds including almond, macadamia and walnut showed no signi cant difference between groups. (data not shown). In the food security & higher-income group, intake of energy, fat, calcium, phos-phorus, iron, potassium, ribo avin, and vitamin C was higher compared to food insecu-rity & low-income group (Table 4). Also, Energy from carbohydrate was lower but energy from fat was higher in the food security & higher-income group than the food insecurity & low-income group. Percentage of participants who took less than Estimated Average Requirement (EAR) for young adults according to household income and food security Percentages of young adults who took less than daily estimated average requirement (EAR) by nutrients were compared and the results were presented in Table 5. Food insecurity & low-income group had higher percentage of young adults who took less than estimated average requirement (EAR) for protein, vitamin A, ribo avin, niacin, vitamin C, calcium, and iron than all other groups (p < 0.05). Food insecurity & low-income group had higher percentage of young adults who took less than EAR for vitamin A than other groups. For phosphorus, the percentage of subjects who took less than EAR in the low-income groups higher compared to those in the high-income groups. In case of vitamin A, vitamin C, and calcium, more than 50% of young adults in the food insecurity & lowincome group took the amount less than EAR a 53.6%, 65.9% and 74.4%, respectively. Most commonly consumed food of young adults according to household income and food security Table 6 shows the result of calculating commercial foods based on intake amount of foods. Food insecurity & low-income group took rice, milk, and beer in order of highest amount while the other groups took rice, beer, and milk in order of highest amount. In the food insecurity & low-income group, ramen took the 11th place, which was relatively higher rank than other groups, and beef and fruit were not included within the 15th place. On the contrary, in the food security & higher-income group and the food insecurity & higher-income group, apples took 11th place respectively and beef took 13th and 14th places, respectively. Another point of interest in that sprite was ranked 12th in the food insecurity & low-income group and 14th in the food security & low-income group, and 18th in the food insecurity & higher-income group but not even on the food security & higher-income group. Relationship between household income and food security and health-related quality of life  OR, Odds ratio; CI, con dence interval; EQ-5D, Euro Quality of Life ve Dimension. 1 Proportions are given as n (%) reporting any problems. 2 Signi cant differences among the study groups were analyzed by χ2 test. 3 The multiple models were adjusted for age, sex, BMI, marital status, residential area, occupation, education level, smoking status, and alcohol consumption.

Discussion
This study was a cross-sectional study conducted to assess the dietary quality of young adults aged 19-34 y in vulnerable group in food-related life and investigate the relationship with the decline of health-related quality of life using KNHANES data from 2008 to 2018. We con rmed that the food insecurity & low-income group had lower foods and nutrients such as fruits, vegetables, sh and shell sh, protein, some vitamins and minerals compared to the food security & higher-income group. In the commonly consumed food, ramen and sprite ranked relatively high in the food insecurity & low-income group while apple and beef ranked high in the food security & higher-income group. In addition, we found that subjects in the food security & low-income group had 55% and 33% higher risk of mobility problem and anxiety/depression respectively.
In this study, total food intake, energy intake, and diet quality were lower in the food insecurity & low-income group than in the food security & higher-income group. Intake of cereal and cereal products was high and intake of vegetables, fruits, sh and shell sh was signi cantly low in the food insecurity & lowincome group. Previous studies have also reported the relationship between food insecurity and intake of low fruit and vegetable [11,39]. In the Canadian dense foods, including fruits and vegetables, are often more expensive and less available in low-income group compared to processed foods. Processed foods are relatively inexpensive and accessible.
In this study, the percentage of participants who took less than estimated average requirement (EAR) of KDRI [38] was calculated to assess diet quality of the subjects. As a result, the food insecurity & low-income group has higher percentage of participants who took less than EAR than other groups in nutrients intake except for carbohydrate. In case of vitamin A, vitamin C, and calcium, the percentage of participants who took less than EAR was more than 50%. In particular, calcium was the micronutrient participants took the most insu ciently and 74.4% of young adults in the food insecurity & low-income group took less than EAR (p < 0.0172). Unlike this, US adults did not show signi cant difference in calcium intake according to food security status [50]. Calcium intake in our study was 471.5-406.7 mg while calcium intake in US women aged 20-70 y between 1999 and 2000 was 756 mg [51], showing that calcium intake of the participants of this study was overall lower than US women and particularly, the participants of the food insecurity & low-income group showed even lower calcium intake. In a systematic review study, most countries in Asia have daily dietary calcium intake less than 500 mg [52]. In addition, this study reported that the calcium intake among Korean adults differed according to income, but Brazil was similar. In our study, although milk ranked second and third in the most consumed foods, consumption of milk and dairy products, which are major sources of calcium, seems to be lower than that of Western countries.
As in previous studies [8,24], this study con rmed that there was a relationship between food insecurity and worse health-related quality of life. In particular, mobility problem and anxiety/depression prevalence of vulnerable group in dietary life, which was the food insecurity & low-income group, was signi cantly increased in this study. Many studies have reported the relationship between food insecurity and mental health [3,53,54]. Meta-analysis for food insecurity and mental health was performed using 19 studies from ten different countries and the results showed that food insecurity increased risk of depression This study has some limitations. As KNHANES is a cross-sectional study, we could not con rm the causal relationship between EQ-5Ds and income and foodsecurity. Furthermore, since we used a single 24-hour dietary recall data, which may not be su cient to estimate the usual dietary intake. Also, there is a limit to absolutely evaluate the lack of nutrients intake using EAR. Therefore, the results of this study had to be interpreted as a relative evaluation of groups classi ed by food security status and income level. Also, food security was determined using a single question asking household food insu ciency, which may not be su cient to measure the food security status. Using a single item for measuring food security status could underestimate the prevalence of food insecurity as its low sensitivity [55]. A validation study conducted in Korea assessed the sensitivity and speci city of KNHANES's a single item question with the developed food security measures based on the US household food security survey module [34]. The sensitivity and speci city of the food insu ciency question were 56.8% and 92.3%, respectively. This is consistent with the previous studies [55][56][57]. On the other hand, Urke et al. [58] reported that a single question for measuring food security could be a useful tool in a large-scale investigation in terms of rapid assessment. Nevertheless, This study has an advantage in that it was a large population-based study and the rst study that analyzed the relationship between household income and food security and health-related quality of life (EQ5D) in Korean young adults.

Conclusions
Income level and food insecurity status in Korean young adults had a relationship with dietary intake status and health-related quality of life, and in particular, mobility and anxiety/depression. Therefore, there is a need to take measures for supporting nutrients for such vulnerable group in dietary life and improving their accessibility to healthy and fresh food. Also, the present study could be used as basic data for the development of government support policies to mitigate gap and inequality in young adults' dietary life and health.