Vitamin D status among Israeli medical residents

Background: Israel is a country with a sunny climate; however, vitamin D deficiency and insufficiency are common findings in certain populations whose exposure to sunlight is limited. Medical residency is known for long indoor working hours, thus theoretically limiting the opportunities for sun exposure. Objectives: To evaluate whether the vitamin D status among residents in a single medical center in Tel Aviv is below the normal range. Methods: Forty-six residents (28 females, 18 males, average age 33.9 ± 2.8 years) in three residency programs (internal medicine, general surgery/obstetrics and gynecology, pediatrics) were recruited. Demographic data, personal lifestyle, physical activity details and sun exposure duration were obtained by a questionnaire. Serum levels for 25(OH)D were analyzed by a radioimmunoassay. Results: The mean serum 25(OH)D concentration was 29.8 ± 5.8 ng/ml. According to Institute of Medicine definitions, none of the residents were vitamin D deficient and only two residents (4%) were vitamin D insufficient (15 ng/ml each). The level of 25(OH)D was similar among the various medical specialties. The 25(OH)D levels correlated with the duration of sun exposure and the number of offspring (regression analysis: R² = 9.2%, P < 0.04 and R² = 8.9%, P < 0.04, respectively), but not with nutritional data, blood chemistry, or extent of physical activity. Conclusions: Most of the residents maintained normal or near normal 25(OH)D levels, indicating that the residency program itself did not pose a significant risk for vitamin D deficiency.