Investigation Of Nutritional Status And Influencing Factors Of Vitamin A And D Among 2-6 Years Children In 12 Cities In Central And Western China

Part Ⅰ: Investigation Of Nutritional Status And Influencing Factors Of Vitamin A Among 2-6 Years Children In 12 Cities In Central And Western ChinaBackground: Early childhood is a critical period for physical growth and neurodevelopment.Ensuring adequate nutrition during this period can effectively reduce the incidence of infectious diseases and even non-communicable diseases in adulthood.Vitamin A(VA)is an essential micronutrient that plays a crucial role in regulating vision,immune response,maintaining epithelial cell integrity,reproductive function,tissue growth,and metabolism.Historically,China has been considered a high-risk area for vitamin A deficiency among children and adolescents,particularly in economically disadvantaged regions such as central and western China.In recent years,with the improvement in living standards,the nutritional status of vitamin A among children and adolescents has shown some improvement.However,the question of whether previous policies of high-dose or general population supplementation of vitamin A should continue has been raised.Despite this,there has been no large-scale epidemiological investigation on vitamin A among children under six years old in the general population since the China National Nutrition and Health Survey was conducted from 2010 to 2013.Currently,data related to vitamin A nutrition in the "Chinese Expert Consensus on Clinical Application of Vitamin A and Vitamin D in Children," published in 2021,still rely on the results of the China National Nutrition and Health Survey(2010-2013).Therefore,it is imperative to conduct a large-scale survey on the nutritional status of vitamin A among children.Previous epidemiological studies have consistently shown poor vitamin A nutrition in the central and western regions.Understanding the vitamin A nutritional status in these regions will further help determine the baseline of vitamin A nutrition in China and provide partial basis for the development of nutritional intervention policies regarding vitamin A supplementation.Objective: The objective of this study is to investigate the nutritional status of vitamin A among 2-6-year-old children in central and western China,as well as analyze its influencing factors,in order to provide evidence for preventive supplementation.Method: This study is a cross-sectional investigation conducted in multiple centers.From November 2018 to September 2019,a total of 2,198 children aged 2-6 years from 12 regions across 8 provinces and municipalities in central and western China were surveyed.Based on local economic statistics,cities are divided into five levels: First-class cities include municipalities directly under the central government,special administrative regions,and cities with a GDP greater than 160 billion and a population greater than 2 million;Second-class cities include other provincial capitals,vice-provincial cities,economic special zones,Suzhou,and Wuxi;Third-class cities include coastal economic open cities,economically developed cities,and high-income cities totaling 14;Fourth-class cities include other cities with a population of over 1 million and key economic cities;Fifth-class cities include other famous economic cities,important transportation hubs,and key tourist cities with a population exceeding 500,000.This paper does not list and analyze the fifth-class cities separately,and the fifth-class cities and below are analyzed as a group,which is referred to as the fifth-class cities in this paper.The sampling method used was a stratified cluster sampling technique.The survey took place in local kindergartens,where the children were selected as clusters based on their classes.The survey covered various aspects,including the assessment of vitamin A and vitamin D levels,as well as measurements of height and weight.Additionally,the children’s demographic information was collected through a questionnaire,along with a food frequency intake questionnaire.To determine the levels of vitamin A,a third-party company employed liquid chromatography-tandem mass spectrometry(AB SCIEX Framingham,MA,USA)as the testing method.The analysis involved using a triple quadrupole mass spectrometer equipped with an Agilent Zorbax Eclipse XDB C8 guard column.Results:(1)The final sample size of this study included 2198 individuals,including 152 from Level 1 cities,403 from Level 2 cities,1292 from Level 5 and below cities,and 351 from nationally designated poverty-stricken counties.The final collected serum retinol data sample included 2194 individuals.(2)The average serum retinol level in children aged 2-6 years was 1.15±0.27μmol/L.Among them,the prevalence of vitamin A deficiency(VAD)was 2.6%(58/2194),and the prevalence of marginal vitamin A deficiency(MVAD)was 32.9%(721/2194).With increasing age,serum retinol levels in children aged 2-6 showed a decreasing trend,and there were significant differences in serum retinol levels among all age groups except between the4-year-old and 5-year-old groups(P<0.05).(3)The proportion of children aged 2-6 years still receiving vitamin A supplementation was 5.4%.Children who received vitamin A supplementation had significantly higher serum retinol levels compared to those who did not receive supplementation(P<0.05).Among children receiving vitamin A supplementation,no cases of vitamin A deficiency were found,and the proportion of normal serum retinol levels(76.9%)was significantly higher than that in the non-supplemented group(64.3%)(P<0.05).(4)Among children aged 2-6 years,5.4% consumed vitamin A supplements.The proportion of vitamin A supplement consumption was higher in children aged 2-3 years(11.3%)and 3-4 years(6.7%)compared to the 4-5 years age group(3.4%).The vitamin A supplement consumption rates were similar among different age groups after 4 years old.(5)The distribution of serum retinol levels and the proportion of vitamin A normal(VAN)individuals in different city levels followed a consistent pattern: Level 1 cities(1.28±0.28μmol/L,82.24%)> Level 2 cities(1.15±0.27μmol/L,67.3%)> Level 5 and below cities(1.16±0.27μmol/L,66.2%)> nationally designated poverty-stricken counties(1.03±0.22μmol/L,47.3%).The proportion of vitamin A insufficiency(VAI,including VAD and MVAD)in Level 1 cities was much lower than that in other city levels.Level 2 and Level 5 cities had similar vitamin A levels and incidence of vitamin A insufficiency.However,the vitamin A nutritional status in nationally designated poverty-stricken counties was significantly worse(P<0.05).(6)The serum retinol levels in the central and western regions(1.14±0.27μmol/L)were significantly lower than those in eastern cities(1.19±0.27μmol/L)(P<0.05).The prevalence of VAD and MVAD in the central and western regions(2.8% and 33.4%,respectively)was higher than that in the eastern regions(VAD 0.6%,MVAD 26.5%)(P<0.05).(7)Among families with a per capita monthly income of less than 500 yuan,500-999 yuan,1000-2999 yuan,3000-4999 yuan,and 5000 yuan or more,the incidence of VAI was 51.7%,44.8%,36.9%,26.7%,and 26.8%,respectively.The trend chi-square test showed statistical significance(P<0.05).There were significant differences in VAI incidence among the first four income levels,while there was no significant difference in VAI incidence between families with a per capita monthly income of 3000-4999 yuan and 5000 yuan or more.Serum retinol levels increased with higher family income(P<0.05).(8)After adjusting for factors such as gender,height,weight,etc.,logistic regression analysis was conducted with variables including per capita monthly income,egg and milk supplementation,age,regional economic level,and vitamin A supplementation.The results showed that the proportion of VAN in children aged 2-6 years was positively associated with per capita monthly income(OR=1.18),milk intake frequency(OR=0.91),and regional economic level(OR=0.71).The incidence of VAN was negatively associated with age(OR=0.76).Conclusion: The vitamin A nutritional status of children aged 2-6 years in the central and western regions deteriorates with increasing age.Higher per capita monthly income and better regional economic level are associated with better vitamin A nutritional status.The vitamin A nutritional status in central and western cities is worse compared to eastern cities.The overall rate of vitamin A supplementation is low and decreases with increasing age.Regression analysis suggests that family income,milk intake frequency,age,and regional economic level are influencing factors for vitamin A nutritional status in children aged 2-6 years.Part 2: Investigation Of Nutritional Status And Influencing Factors Of Vitamin D Among 2-6 Years Children In 12 Cities In Central And Western ChinaBackground: Vitamin D(VD)plays an important role in various physiological processes.Long-term deficiency of VD not only affects the absorption of calcium and phosphorus,but also increases the risk of various chronic diseases,such as autoimmune diseases,asthma,cardiovascular diseases,and infections.Children’s rapid growth makes them a high-risk group for vitamin D deficiency,as they have a significant need for VD and other nutrients.With the development of the economy and changes in living environments,the factors influencing the VD nutritional status of the population have gradually changed.However,in the past 10 years,there has been no epidemiological survey on the VD nutritional status of ordinary children in China,and research on the general population of children aged 0-6 is particularly lacking.The data on VD deficiency used in the 2021 Expert Consensus on Clinical Application of Vitamin A and VD in Chinese Children are still based on surveys conducted between 2010 and 2013.It is worth exploring the VD nutritional status and influencing factors among children aged 6 and below in China.A multicenter survey on the VD nutritional status of ordinary children aged 0-6 is of great significance.Previous studies have shown that the VD nutritional status in central and western regions is relatively poor compared to the whole country.Understanding the VD nutritional status in these regions will help formulate relevant VD nutrition policies for economically underdeveloped areas in China.Objective: To investigate the vitamin D nutritional status and analyze the influencing factors among children aged 2-6 in central and western regions of China,providing evidence for preventive supplementation.Methods: Same as Part 1.The standard reference material for vitamin D in human serum is "740217" and "739650" from Sigma.The quantification concentration and detection concentration are 1.2 ng/m L and 0.4 ng/m L,respectively.The intra-day and inter-day precision are 3.27% and 5.97%,respectively.This method is certified through an external quality assurance program for VD.The concentration of 25(OH)D includes the concentrations of 25(OH)D3 and 25(OH)D2.Results:(1)The final sample size in this study was 2,192 individuals,including 1,165 boys(53.1%)and 1,027 girls(46.9%).The average level of 25(OH)D in the overall population was 23.87±8.24ng/ml.Vitamin D deficiency(VDD;25(OH)D<12ng/ml)was present in 5.2% of children,and vitamin D inadequacy(VDI;12≤25(OH)D<20ng/ml)was present in 29.6% of children.(2)There were gender differences in the vitamin D status.Boys had higher levels of 25(OH)D compared to girls(24.3±8.33ng/ml vs.22.66±7.98ng/ml,P<0.05),and the prevalence of vitamin D sufficiency(VDS;25(OH)D≥12ng/ml)was higher in boys compared to girls(70.1% vs.59.6%,P<0.05).(3)Serum 25(OH)D levels decreased gradually with increasing age in children aged 2-6 years.There was no significant difference in serum 25(OH)D levels between the 4-and 5-year-old age groups,but significant differences were observed among the other age groups(P<0.05).As age increased,the proportions of serum VDD(25(OH)D<12ng/ml)and VDI(12≤25(OH)D<20ng/ml)also increased.In the 5-year-old age group,only 53.5% of children had normal vitamin D levels.(4)Serum 25(OH)D levels varied by season.The highest levels were observed in summer(29.60±6.95ng/ml),followed by spring and autumn,and the lowest levels were observed in winter(20.89 ± 8.26ng/ml).Significant differences were observed between seasons,except for spring and autumn(P<0.05).In this study,there was only one case of VDD in summer,and 94.84% of children aged 2-6 years had normal vitamin D levels.There were no significant differences in the proportions of VDD(4.6% in spring,1.0% in autumn)or VDI(28.9% in spring,27.1% in autumn)between spring and autumn(P>0.05),but significant differences were observed among spring,autumn,summer,and winter(VDD: 10.1% in winter,0.4% in summer;VDI: 45.1% in winter,4.8% in summer;P<0.05).(5)Serum 25(OH)D levels varied by geographical location.Among the eight provinces included in the study,coastal cities(Fujian)had the highest levels of serum 25(OH)D and the highest rates of vitamin D sufficiency(29.01 ± 7.02ng/ml,93.4%),followed by Xinjiang(26.89 ± 6.50ng/ml,87.0%),and Chongqing had the lowest levels(22.19±8.70ng/ml,52.0%).(6)Serum 25(OH)D levels varied by urban economic status.Serum 25(OH)D levels were significantly lower in first-tier cities compared to other cities,while no significant differences were observed among other cities.First-tier cities had the highest rates of VDD and VDI,significantly higher than other cities(P<0.05),while no significant differences were observed among the other cities.(7)Serum 25(OH)D levels varied with temperature.There was a significant correlation between the average monthly temperature and serum 25(OH)D levels(P<0.05).For every 1℃ increase in temperature,serum 25(OH)D levels increased by 0.3625ng/ml.When the temperature was above 20℃,the proportion of vitamin D sufficiency gradually increased,and when the temperature exceeded 26℃,the proportion of vitamin D sufficiency reached or approached 100%.(8)Serum 25(OH)D levels varied with food intake.Children aged 2-6 years who consumed dairy products,eggs,and seafood at least 3 times per week had higher levels of serum 25(OH)D and a higher prevalence of VDS(25(OH)D≥12ng/ml)(P<0.05).Children who consumed meat products at least 3 times per week had even higher levels of serum 25(OH)D(P<0.05),but there was no significant difference in the proportion of VDS(P>0.05).(9)Serum 25(OH)D levels varied with vitamin D supplementation.The overall prevalence of vitamin D supplementation among children aged 2-6 years was low(5.4%).Vitamin D supplementation rates decreased with increasing age before the age of 5.There was no significant difference in vitamin D supplementation rates between the 4-and 5-year-old age groups.Children who received vitamin D supplementation had significantly higher levels of serum 25(OH)D compared to those who did not receive supplementation(29.37±6.80ng/ml vs.23.15±8.16ng/ml,P<0.05).In this study,no cases of vitamin D deficiency were observed among children who received vitamin D supplementation.(10)Factors influencing serum 25(OH)D levels after adjusting for WAZ(weight-for-age Z-score),HAZ(height-for-age Z-score),and BAZ(body mass index-for-age Z-score): Logistic regression analysis was performed with gender,age,season,vitamin D supplementation,frequency of milk consumption,frequency of egg consumption,frequency of seafood consumption,latitude,temperature(average monthly temperature at the time of sampling),and sampling location as independent variables.Serum 25(OH)D concentration was negatively correlated with age(OR=0.46).Vitamin D supplementation(OR=10.64),dairy product consumption(OR=1.16),egg consumption(OR=1.21),and average monthly temperature at the time of sampling(OR=1.19)were positively correlated with serum 25(OH)D levels.In this study,there were no significant correlations between vitamin D status and family income or latitude(P>0.05).Conclusion: The vitamin D nutrition status of children aged 2-6 years in central and western China has improved compared to previous studies,but the rates of vitamin D deficiency and inadequacy are still relatively high.Overall,boys have better vitamin D nutrition than girls.Vitamin D nutrition and supplementation rates gradually decline with increasing age.Season remains an important factor influencing vitamin D nutrition,and higher local temperatures are associated with better vitamin D nutrition.Compared to eastern coastal cities(Fujian),cities in central and western China,especially Chongqing,have lower vitamin D nutrition,indicating that the economic status of a region is not the major determinant of vitamin D nutrition,but rather its geographical or urban characteristics.Consumption of dairy products,eggs,and vitamin D supplementation are positively associated with vitamin D nutrition.Latitude has a minor influence on vitamin D nutrition in children aged 2-6 years in central and western China but is not a major contributing factor.