To investigate the trends and influencing factors of vitamin D nutritional status among primary and secondary school students in Guizhou Province from 2012 to 2023, providing scientific basis for formulating nutritional improvement measures.

A multi-stage cluster sampling method was adopted to select one primary and one secondary school from each of the survey sites implementing the “Nutrition Improvement Program for Rural Compulsory Education Students” in Guizhou Province. A total of 9 830 students were surveyed with questionnaires and had their blood samples tested.The prevalence rates of each year were standardized using the population age structure of 2023. The Mann-Whitney U test was used to compare the differences in vitamin D levels between different genders, and the Kruskal-Wallis H test was used to compare the differences among different age groups. The Bonferroni method was used to correct the significance level for two-group comparisons. The Spearman rank correlation analysis was used to test the trend of vitamin D levels over the years. The quantile regression model was used to examine whether there were differences in the trend of vitamin D levels among different subgroups.

Vitamin D levels among primary and secondary school students in Guizhou Province fluctuated between 2012 and 2023, but showed an overall upward trend (r_s=0.048, P<0.001), rising from 21.1 ng/ml in 2012 to 22.6 ng/ml in 2023.The vitamin D levels of males were consistently higher than those of females (P<0.05). With increasing age, vitamin D levels showed a downward trend(P<0.05). Except for 2015, the serum 25(OH)D concentrations of the 12-14 and 15-17 age groups were lower than those of the 6-8 age group. The prevalence of vitamin D deficiency (VDD) and vitamin D inadequacy (VDI) was consistently higher in females than in males. The prevalence of VDD and VDI in each age group fluctuated, and in 2023, the prevalence of VDD and VDI in each age group was lower than in 2012. The quantile regression model results indicated that the rate of improvement in vitamin D levels over time was significantly slower in males than in females (β=-0.118, P=0.016). The average annual improvement rate in vitamin D levels was significantly higher in the 6-8 age group than in the 15-17 age group(β=0.261, P<0.001).

The prevalence of VDD and VDI among primary and secondary school students in Guizhou Province remains at a relatively high level. Specifically, targeted nutritional intervention strategies should be developed for females and older males to improve their vitamin D nutritional status.