The Efficacy Of Vitamin D Supplementation Plus Health Education In Promoting Vitamin D Nutritional Status Of Residents In Urbanized Areas

ObjectiveWith the improvement of economic level,the acceleration of urbanization and changes in the social environment,the shift of residents’dietary structure and the reduction in outdoor activities have resulted in the prevalence of vitamin D insufficiency and deficiency among residents in urbanized areas.Vitamin D deficiency has a great negative impact on skeletal health,immune system,endocrine system,etc.Zhejiang Province is experiencing rapid urbanization,with a high prevalence of vitamin D deficiency among residents,which requires an early intervention.However,there is currently no policy guidance for vitamin D interventions for people undergoing rapid urbanization.This study aims to assess the efficacy of the interventions with vitamin D supplementation plus health education in promoting nutritional status of vitamin D in residents undergoing rapid urbanization.The results will providing important information for the developing a policy and protocol for nutritional intervention.MethodsFrom February to June 2022,62 residents with vitamin D deficiency living in recent urbanized areas were screened and recruited.They were randomly assigned into an intervention group and a control group.Those in intervention group were supplemented with vitamin D₃（400 IU per day for three months）and given health education（once a month for three months）,which were initiated in July 2022.No intervention was given to the control group.Before and after the intervention,questionnaires,physical measurements and biochemical examinations were performed on all study subjects.Serum 25-hydroxyvitamin D concentrations were detected by liquid chromatography-tandem mass spectrometry（LC-MS/MS）.Results1.Baseline:There were no significant differences between the intervention group and the control group in terms of age,sex,education level,marital status,occupation,height,weight,waist circumference,dietary score,sleep time,outdoor time,blood lipid（LDL-C,HDL-C,TG,TC）and serum 25-hydroxyvitamin D level.2.Intervention effect:Vitamin D levels were elevated to varying degrees in both the intervention and control groups compared with baseline.The serum level of 25-hydroxyvitamin D in the intervention group increased from（14.3±3.8）ng/ml to（22.2±8.9）ng/ml（t=-5.006,P<0.001）and the control group increased from（14.6±3.4）ng/ml to（19.8±8.4）ng/ml（t=-3.281,P=0.003）,the differences of pairing t-test between the before and after in two groups both were statistically significant.The intervention group increased by（7.9±8.8）ng/ml compared with the baseline;The control group increased by（5.2±8.8）ng/ml,and there was no significant difference between before and after intervention in two groups（independent samples t test,t=1.191,P=0.238）.After the intervention,the vitamin D nutritional status of the two groups also changed to varying degrees.In the intervention group,18（58.1%）changed from vitamin D deficiency or insufficiency to normal,11（35.5%）in the control group became normal,and there was no significant difference in the distribution of vitamin D nutritional status between the two groups after intervention（χ²=3.175,P=0.075）.3.Stratified analysis of intervention effect:In the population with baseline vitamin D insufficiency,the serum level of 25-hydroxyvitamin D in the intervention group increased by（8.2±9.4）ng/ml compared with the baseline,and the control group increased by（3.1±7.2）ng/ml,and there was no significant difference in the post-intervention increase between the two groups（t=1.973,P=0.055）.In the population with baseline vitamin D deficiency,serum 25-hydroxyvitamin D levels increased by（7.2±7.8）ng/ml in the intervention group and（9.7±10.6）ng/ml in the control group,and there was no significant difference in post-intervention increase between the two groups（t=0.586,P=0.565）.At baseline,there were 21 cases of vitamin D deficiency in both groups.76.2%of the intervention group turned normal after the intervention（16 cases）,while only 33.3%of the control group turned normal（7 cases）,and the difference was statistically significant（χ²=7.785,P=0.005）.4.Analysis of influencing factors of intervention:Combining intervention and control group data,multiple linear regression analysis showed that age（β=0.223,95%CI:0.06,0.39;P=0.009）and vitamin D supplementation intervention（β=4.099,95%CI:0.15,8.04;P=0.042）were positively correlated with changes in serum 25-hydroxyvitamin D concentration;and outdoor time during the day（β=-0.790,95%CI:-1.48,-0.10;P=0.026）and baseline serum 25-hydroxyvitamin D concentration（β=-0.740,95%CI:-1.29,-0.19;P=0.009）were negatively correlated with changes in serum 25-hydroxyvitamin D concentration.The effects of each variable on the changes of vitamin D before and after the intervention were age,baseline 25-hydroxyvitamin D,time of outdoor activities,and whether to supplement vitamin D.Conclusions1.Supplementation of 400 IU of vitamin D per day for three months plus health education led to a significant increase in serum 25-hydroxyvitamin levels in vitamin D deficiency or insufficiency in study subjects;however,compared with the control population,no significant effect of the intervention on improving the body’s vitamin D level and improving vitamin D nutritional status was observed.2.In people with vitamin D deficiency,supplementation with 400 IU of vitamin D per day for three months plus health education can effectively improve vitamin D levels and improve vitamin D nutritional status.3.The effect of vitamin D supplementation is affected by season,baseline 25-hydroxyvitamin D concentration,age,outdoor activity time and other factors.