The present study evaluated the growth and nutritional status of preschool children in the most northern and coldest parts of China. We found the coexistence of stunting and overweight/obesity, the so-called “double burden” of malnutrition, in the region. We also found that stunting mainly occurred in girls, while boys had a higher risk of obesity. Moreover, vitamin 25-(OH)-D3 deficiency was common (88.85%), which should draw much attention for nutritional interventions.
In this study, the physical development of boys and girls was in accordance with the general trend of childhood growth; that is, the height, weight and head circumference gradually increased with age, and the total development levels were better in boys than in girls. Compared with China’s growth reference, the height was lower, but the weight and head circumference were similar among preschool children in Daxing’anling. This might be related to the local cold climate. The winter is long and daylight is short, and the children's outdoor exercise was relatively low. Our results were consistent with the Northern Finland survey. However, the physical development levels were close to or met the WHO standard. Due to the development of the economy and the improvement of people's living standards, the physical development of preschool children in this area was relatively good.
Growth and development levels were between − 1 SD and + 1 SD, similar to those of children in Jordan. WAZ is sensitive to recent nutritional changes in children. It was found that WAZ was relatively low among children aged 3 to 4 years. The main reason may be that children aged 3 to 4 years may be accustomed to a children’s diet, and as they gradually enter the adult’s diet model, the composition or intake of food changes. If children do not adapt to these changes, growth will be affected. WHZ is a sensitive indicator that reflects acute nutritional status. Weight for height Z scores were more than − 1 SD among 92.55% of children, indicating that the children were slightly overweight, although the nutritional status of children was generally good. HAZ mainly reflects the long-term and chronic nutritional status of the past. In total, 83.28% of children had a HAZ greater than − 1 SD, which is significantly higher than children in Central Brazil. Head circumference growth was accompanied by an increase in brain capacity. HCZ can reflect the brain development of children. In this study, the levels of head circumference were normal in most children.
Compared with other areas in China, our results showed that the rates of underweight, stunting and wasting in Daxing’anling were lower than those of Wuzhong, a city in Northwest China; the rates of overweight and obesity were higher than those of Xiamen, a city in Southeast China. Similarly, compared with other developing countries, the rates of undernutrition were lower than those of Indonesia. The prevalence of overweight was higher than that of Brazil, and the prevalence of obesity was also higher than that of Ethiopia. However, because of the cold temperature in Daxing’anling, the intake of meat and other fatty foods is relatively high, while outdoor exercise is less than in warm places. Therefore, cold temperatures might be an important reason for the high rate of obesity in preschool children. In our study, the prevalence of obesity was higher in boys than in girls, consistent with the Tianjin survey.
It was shown that children with high birth weights might have a higher risk of obesity, although there were no significantly difference in the rates of obesity and overweight between children with high birth weights and with normal birth weights. Although the birth weight reflected the nutritional status of the foetus in the uterus, it could also indicate a strong ability to absorb nutrients. More nutrients and energy are consumed after birth, eventually leading to overnutrition. The problem of overnutrition in children is especially prominent in cold areas of China and is related to dietary habits, a short outdoor time and a long resting time. Consequently, it is essential to strengthen nutritional interventions, focusing on the importance of a balanced diet, children's behaviour and outdoor exercise. Interventions could contribute to improving parents' knowledge levels and health awareness in various ways and help children develop good habits. Finally, it could not only effectively promote the growth and development of children but also improve their nutritional status.
Our study suggested that the levels of vitamins among preschool children were not good. Further study is needed to investigate the risk factors of vitamin A and D deficiency. The rates of marginal vitamin A deficiency were lower than those of Chongqing, a mountain area in Southwest China. However, vitamin D deficiency was serious in this area, and the prevalence of vitamin D deficiency was higher than that in Hangzhou, China, and Nepal. The reason was probably that Hangzhou and Nepal are sunny areas and are much warmer than Daxing’anling. Therefore, children may stay outdoors longer. In our study, the levels of vitamin D in children aged 6 years had improved, which might be related to the increased resistance to diseases and outdoor activities. 25-(OH)-D3 was positively associated with Vitamin A. Thus, parents should always take their children out in the sunshine.
Strengths and Limitations
In the current study, stratified cluster random sampling in four kindergartens according to the geographical location, climate, economic and cultural levels was used to reflect the average levels of the local region. In addition, the questionnaires from the preschool children’s parents were completed via face-to-face interviews. Therefore, the data could be considered representative and credible. Although our study had a number of strengths, it was subject to several limitations. First, its cross-sectional design restricted the drawing of causal inferences. Additionally, the findings referred specifically to preschool children in Daxing'anling, the coldest region of China, and thus cannot be generalised to others. Finally, there was not enough background information to comprehensively compare the present health status of preschool children.