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

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. [ABSTRACT FROM AUTHOR]