Diet, physical activity, and UV protection comprehensively influenced vitamin D status in college students: a cross-section study from China

Abstract

Background: Vitamin D deficiency is one of the most prevalent health problems worldwide in all age groups, whereas vitamin D status of Chinese college students was seldom studied in China. The purpose of this study was to explore the vitamin D status in Chinese college freshmen and its influencing factors, providing evidence for nutrition strategy application.

Methods: Information including demographic status, diet habit, physical activity, and ultraviolet ray (UV) protection was collected by online questionnaire. Serum 25(OH)D₃ concentrations were measured using a liquid chromatograph mass spectrometer. Multivariate linear regression analyses were used to explore the comprehensive influence of diet, physical activity and UV protection on serum 25(OH)D₃ levels.

Results: Totally 1667 freshmen from 26 provinces, autonomous districts or municipalities, were recruited, with a mean age of 18.6 ± 0.9 years. The mean serum 25(OH)D₃ levels were 18.1 ± 6.3 ng/mL and the proportion of vitamin D deficiency and insufficiency was 67.5% and 27.8%, respectively. Multivariate linear regression indicated that higher intake of milk and yogurt, calcium or vitamin D supplementation, and longer time of outdoor activity were positively linked to higher serum 25(OH)D₃, while higher intake of candy and higher UV protection index were negatively associated with serum 25(OH)D₃, after adjusted for age, gender, region of original residence, latitudes, longitude and BMI.

Conclusions: Vitamin D deficiency is very common in Chinese college students. Milk and yogurt intake and outdoor activity should be encouraged while candy intake should be limited for preventing vitamin D deficiency. Public health policies should focus on these changeable lifestyles and consider well-balanced guidelines on UV protection and vitamin D supplementation.

Keywords: Dietary intake; Physical activity; Serum 25(OH)D3; UV protection; Vitamin D deficiency.

Fig. 1

A Serum 25(OH)D₃ levels in different UV protection categories (n = 1667). B Serum 25(OH)D₃ levels in different UV protection index categories (n = 1667)