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

Abstract

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 (23º 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.

Association between Night-shift Work and Serum 25-hydroxyvitamin D Levels in Japanese Male Indoor Workers: A Cross-sectional Study

“…The apparent lack of association between night-shift work and 25OHD is consistent with a previous study that demonstrated serum 25OHD concentrations during summer did not significantly differ among physicians working at least one night shift a week, medical students, or indoor workers 8) . In addition, a comparison of female nursing-home workers with or without a single weekly night shift found no significant association between night-shift work and serum 25OHD concentrations measured in winter after controlling for relevant factors, such as age and sunshine duration 9) .…”

“…First, the small number of subjects limited the statistical power to detect differences among the worker groups. Although the present data should be considered as preliminary, the findings are of value, given the little evidence that exists concerning the association between night-shift work and 25OHD 8,9) . Second, it is not clear how our results could be generalized to other shift-working men or women, even though it is known that 25OHD levels in men would be higher than those in women a priori 6) .…”

“…Although low vitamin D status resulting from night work is a suspected cause of night-shift work-related health problems 2) , few studies have investigated the association between night-shift work and circulating 25OHD levels. To date, the findings related to 25OHD levels have presented mixed results 8,9) . Clarification of the effect of night work on an individual's vitamin D status would allow the development of effective countermeasures for protecting night-shift workers from bone fracture and other hypovitaminosis D-related health problems.…”

No association between 25-hydroxyvitamin D levels and prediabetes in Brazilian patients. A cross-sectional study

“…In healthy teenagers and young adults, the prevalence was 60% and 50% respectively. 6,7 Since prediabetes is an early stage of T2DM in which the metabolic process has already started, prevention efforts at this stage have greater impact in mitigating the development of T2DM. 8,9 Several clinical studies have evaluated the role of low 25OHD3 in the pathogenesis of T2DM, but with controversial results.…”

Vitamin D status in a sunny country: Where has the sun gone?

“…3 However, Brazilian studies have been crosssectional, and only evaluated specific populations narrow age ranges such as children, 4 adolescents, 5 healthy young 6 and elderly people 7 from different regions of the country. There is no prospective data regarding seasonal effects of UV exposure on s25 (OH)D. São Paulo is the largest city in Brazil and the world's 7th largest metropolitan area, with almost 20,000,000 residents, comprising more than 10% of the entire Brazilian population.…”