Article

Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: An ecologic meta-regression analysis

Department of Endocrinology and Metabolism C, Aarhus Amtssygehus, Aarhus University Hospital, Aarhus, Denmark.
Osteoporosis International (Impact Factor: 4.17). 05/2008; 20(1):133-40. DOI: 10.1007/s00198-008-0626-y
Source: PubMed

ABSTRACT We performed a meta-analysis of cross-sectional studies on serum 25(OH)D status globally. Serum 25(OH)D levels on average were 54 nmol/l, were higher in women than men, and higher in Caucasians than in non-Caucasians. There was no trend in serum 25(OH)D level with latitude. Vitamin D deficiency was widespread.
We studied vitamin D status (expressed as serum 25-hydroxy-vitamin D [25(OH)D]) in native subjects worldwide.
Meta-analysis and meta-regression of studies reporting on 25(OH)D in healthy subjects retrieved from Pubmed, Embase and Web of Science using the terms "serum", "25-hydroxy-vitamin D", "cholecalciferol", and "human". A total of 394 studies were included.
The mean 25(OH)D level was 54 nmol/l (95% CI: 52-57 nmol/l). Women had borderline significantly higher 25(OH)D levels than men, and Caucasians had higher levels than non-Caucasians. 25(OH)D levels were higher in subjects aged >15 years than in younger subjects. Unadjusted there was no significant decrease in 25(OH)D with latitude (slope of curve -0.03 +/- 0.12 nmol/l per degree latitude north or south of equator, p = 0.8). There was a significant decline with latitude for Caucasians (-0.69 +/- 0.30 nmol/l per degree, p = 0.02), but not for non-Caucasians (0.03 +/- 0.39 nmol/l per degree, p = 0.14). After adjustment for age, gender, and ethnicity, no overall correlation was present between 25(OH)D and latitude (-0.29 +/- 0.24 nmol/l per degree, p = 0.23).
There was no overall influence of latitude on 25(OH)D. However, in separate analyses 25(OH)D decreased with latitude in Caucasians but not in non-Caucasians. A widespread global vitamin D insufficiency was present compared with proposed threshold levels.

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    • "The effect of latitude and season on vitamin D concentrations is well documented in humans, where people living closer to the equator have higher vitamin D concentrations due to longer periods of sunlight (Hagenau et al., 2009; Mithal et al., 2009). Of interest and supporting the importance of sunlight exposure, the highest rates of hypovitaminosis D and rickets in the world are reported in the Middle East and Africa (Hagenau et al., 2009; Mithal et al., 2009). This is explained by ethnicity, cultural and religious practices (body covering, veils), prolonged breastfeeding, and inhabitants with darker skin color. "
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