The effect of sun exposure on 25-hydroxyvitamin D concentrations in young healthy subjects living in the city of São Paulo, Brazil

• Published in: Brazilian journal of medical and biological research Vol. 40; no. 12; pp. 1653 - 1659
• Main Authors: Maeda, S S, Kunii, I S, Hayashi, L, Lazaretti-Castro, M
• Format: Journal Article
• Language: English
• Published: Brazil Associação Brasileira de Divulgação Científica 01.12.2007
• Subjects: 25-Hydroxyvitamin D; 25OHD and solar exposure; Adolescent; Adult; BIOLOGY; Brazil; Female; Humans; Immunoradiometric Assay; Male; MEDICINE, RESEARCH & EXPERIMENTAL; Occupational aspects; Parathyroid hormone; Reference Values; Seasonal influence; Seasons; Statistics, Nonparametric; Sunlight; Time Factors; Vitamin D - analogs & derivatives; Vitamin D - blood; Seasonal influence; Occupational aspects; Parathyroid hormone; 25OHD and solar exposure; 25-Hydroxyvitamin D
• ISSN: 0100-879X; 1414-431X; 1414-431X
• DOI: 10.1590/s0100-879x2006005000162

The range of 25-hydroxyvitamin D (25OHD) concentration was determined in a young healthy population based on bone metabolism parameters and environmental and behavioral aspects. We studied 121 healthy young volunteers (49 men, 72 women) living in São Paulo (23 masculine 34' south latitude) belonging to three occupational categories: indoor workers (N = 28), medical school students (N = 44), and resident physicians (N = 49). Fasting morning blood samples were collected once from each volunteer from August 2002 to February 2004, and 25OHD, total calcium, albumin, alkaline phosphatase, phosphorus, creatinine, intact parathyroid hormone, osteocalcin, and type I collagen carboxyterminal telopeptide were measured. Data are reported as means +/- SD. Mean subject age was 24.7 +/- 2.68 years and mean 25OHD level for the entire group was 78.7 +/- 33.1 nM. 25OHD levels were lower (P < 0.05) among resident physicians (67.1 +/- 27.0 nM) than among students (81.5 +/- 35.8 nM) and workers (94.0 +/- 32.6 nM), with the last two categories displaying no difference. Parathyroid hormone was higher (P < 0.05) and osteocalcin was lower (P < 0.05) among resident physicians compared to non-physicians. Solar exposure and frequency of beach outings showed a positive association with 25OHD (P < 0.001), and summer samples presented higher results than winter ones (97.8 +/- 33.5 and 62.9 +/- 23.5 nM, respectively). To define normal levels, parameters such as occupational activity, seasonality and habits related to solar exposure should be taken into account. Based on these data, we considered concentrations above 74.5 nM to be desired optimal 25OHD levels, which were obtained during the summer for 75% of the non-physicians.