Seasonal Variations of Vitamin D in Vegetarians

Aim: Adequate levels of vitamin D are vital for bone homeostasis throughout the life cycle, especially at older ages. We aimed to assess 25-hydroxivitamin status and seasonality variations in a sample of vegetarians stratified for age and gender. Methods: The study included 347 vegetarians, whose serums were collected between March and May (before summertime-PreS) and then between August and September (after summertime-PostS). Serum 25-hydroxyvitamin (Vitamin D) was measured by an automated immunoassay (ARCHITECT, Abbott). Results: PreS samples showed a Vitamin D median of 18.3 ng/mL and 57% resulted as deficient (<20 ng/mL) while only 13% resulted as sufficient (>30 ng/mL). The deficient fraction was the mode class at all ages. No statistically significant differences among age and sex classes were detected. PostS samples showed a Vitamin D median of 36.0 ng/mL with a significant increase of 32% as compared to PreS; 26% resulted as deficient while only 36% resulted as sufficient. In subjects aged >69 years this increase was statistically smaller than in other age groups. Mode was the sufficient class up to 49, the insufficient class (20-30 ng/mL) between 50 and 69 and the deficient class over 69 years. Conclusions: These results confirm that exposure to the sun increases the levels of vitamin D in young and middle-aged vegetarians but not in the elderly and highlight the need for dietary strategies to increase vitamin D intake especially in the older age classes.