Is sunlight enough for sufficient vitamin D status in children and adolescents? A survey in a sunny region of southern Italy

Objectives: Because it is involved in calcium homeostasis, vitamin D is a prohormone with many implications for health, especially bone health. Hypovitaminosis D is considered pandemic worldwide, with important health health consequences. The aim of our study was to evaluate vitamin D levels in children living in a southern region of Italy with high exposure to sunlight for at least 5 mo a year along with contributing factors.

Methods: A total of 1484 children and adolescents (age 0.02-17.74 y) living in the Apulia region (Southern Italy) were studied. Serum 25-hydroxyvitamin D (25[OH]D) concentrations were assessed and vitamin status defined as follows: deficiency with serum 25(OH)D < 20 ng/mL, insufficiency from 20 to 29.9 ng/mL, and sufficiency with serum 25(OH)D from 30 to 100 ng/mL.

Results: The median serum 25(OH)D levels were 20.2 ng/mL (interquartile range, 14.5-26.4 ng/mL): 48.9% of the overall population had 25(OH)D < 20 ng/mL and only 15% had sufficient 25(OH)D values. There was an inverse association between blood levels of 25(OH)D and age (P < 0.001, ρ: -0.113). Significant 25(OH)D variations were recorded according to the season in which blood samples were drawn, but even during summer only 32.6% of analyzed children had sufficient 25(OH)D levels.

Conclusions: More than 80% of our population had 25(OH)D less than sufficiency cutoff levels. Results highlight a high prevalence of 25(OH)D deficiency in our area, even during summer. It is important to establish screening, supplementation guidelines, and pediatric cutoff levels to optimize vitamin D status in children, taking into account age, nutritional status, and seasonality.