Meta-analysis vit D not change with latitude unless caucasian 2009
Osteoporos Int. 2009 Jan;20(1):133-40. Epub 2008 May 6.
Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: an ecologic meta-regression analysis.
Hagenau T, Vest R, Gissel TN, Poulsen CS, Erlandsen M, Mosekilde L, Vestergaard P.
Department of Endocrinology and Metabolism C, Aarhus Amtssygehus, Aarhus University Hospital, Aarhus, Denmark.
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. INTRODUCTION: We studied vitamin D status (expressed as serum 25-hydroxy-vitamin D [25(OH)D]) in native subjects worldwide. 
METHODS: 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 &quot;serum&quot;, &quot;25-hydroxy-vitamin D&quot;, &quot;cholecalciferol&quot;, and &quot;human&quot;. A total of 394 studies were included. 
RESULTS: 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 &gt;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). 
CONCLUSION: 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.

PMID: 18458986 [PubMed - indexed for MEDLINE]