Vitamin D nutritional status and dietary calcium intake of children and adolescents in Zhejiang Province, China

Abstract Background Low 25-hydroxyvitamin D (25-(OH)D) serum levels, and a nutritional calcium deficit are widely encountered in China. However, few studies have determined the the calcium dietary intake and the corresponding food sources, and few studies have investigated investigated the influencing factors of serum 25-(OH)D. Objective This study was conducted to explore the vitamin D and calcium nutritional status among children and adolescents. Methods This study included children and adolescents aged 6–17 years who participated in provincial nutrition surveillance, which was including 90 counties (cities and districts) in Zhejiang Province with provincial representative. Food consumption was assessed using three consecutive days of 24-h dietary recall, and nutrient intake were calculated using dietary recall in conjunction with the China Food Composition Table. Blood sample were collected to detect the concentration of 25-hydroxyvitamin D by enzyme linked immunosorbent assay. Results The analysis included a total of 1827 children and adolescents. The prevalence of vitamin D deficiency in 6–8, 9–11, 12–14 and 15–17 age groups were 2.3%, 4.75%, 8.33% and 16.98% respectively. The prevalence of vitamin D inadequacy in 6–8, 9–11, 12–14 and 15–17 age groups were 24.33%, 34.50%, 45.5% and 43.24% respectively. The medians of dietary calcium intake in 6–8, 9–11, 12–14 and 15–17 age groups were 336.5, 359.4, 323.4 and 320.47 milligrams per day (mg/d), respectively. The main food sources of dietary calcium were dairy and vegetables. The Spearman's rho of dietary calcium and dairy in 6–8, 9–11, 12–14 and 15–17 age groups were 0.627, 0.660, 0.637, and 0.479, respectively(P < 0.001) and the Spearman's rho of dietary calcium and vegetables in 6–8, 9–11, 12–14 and 15–17 age groups were 0.424, 0.410, 0.447, and 0.440, respectively(P < 0.001). The concentration of serum 25-(OH)D were correlated with sleep time of study days in 6–8 and 9–11 age groups (Spearman’s rho = 0.09, 0.095, p < 0.05). The dietary calcium intake of children and adolescents of 15–17 age groups were positively related to outdoor activities (Spearman’s rho = 0.207, p < 0.05). Dairy intake were negatively related to the sleep time of rest days and outdoor activity time among children and adolescents of 9–11 age group (Spearman’s rho=-0.219, -0.199, p < 0.05). Conclusions There was a high prevalence of inadequacy and deficiency of vitamin D in children and adolescents and their dietary calcium intake were severely insufficient. Dairy are the most effective food sources for improving dietary calcium intake. Nutrition education to increase dairy products intake should be conducted and more opportunities should be provided children and adolescents to receive sunlight exposure to improve the vitamin D nutritional status.