Background: Hypovitaminosis D is common worldwide, even in sunny regions.

Objectives: To assess the prevalence and determinants of vitamin D deficiency in toddlers.

Methods: A cross-sectional prospective study was conducted in healthy Jewish children aged 1.5–6 years at five primary care pediatric clinics in the Jerusalem area during the period October 2009 to November 2010. Parents were interviewed regarding personal and demographic data and sun exposure. Blood samples were obtained for serum 25-hydroxyvitamin D [25-OHD] level. Vitamin D deficiency and insufficiency were defined as 25-OHD < 20 ng/ml and < 30 ng/ml, respectively.

Results: Of 247 children studied, 188 (76%) were ultra-Orthodox and 59 (24%) were Orthodox, traditional or secular. Mean (± SD) 25-OHD level was 25.7 ± 10 ng/ml. Only 73 children (29.6%) had sufficient 25-OHD levels, 104 (42.1%) had insufficiency, and 70 (28.3%) had 25-OHD deficiency. The difference between ultra-Orthodox and others was insignificant (25 ± 10 vs. 27.8 ± 10.5 ng/ml respectively, P = 0.062). Children aged 1.5–3 years had higher 25-OHD levels than those aged 3–6 years (28.6 ± 10.7 and 24 ± 9.2 ng/ml respectively, P < 0.001). Vitamin D deficiency was more common in winter (53%) and autumn (36%) than in summer (19%) and spring (16%). Toddlers attending long-day kindergartens had higher 25-OHD level than those staying at home or at short-day kindergartens (28.8 ± 11.5 and 24.7 ± 9.6 ng/ml respectively, P < 0.05).

Conclusions: A high prevalence of vitamin D deficiency was found in toddlers in our study, mainly in older children and in the winter and autumn. We recommend routine supplementation of vitamin D for children beyond the agear.