This study examined the relationship between vitamin D deficiency and osteoporosis, risk of cancer, and cardiovascular disease. In a systematic literature review using the Medline and EMBASE databases, the authors identified 195 studies conducted in forty-four countries involving more than 168,000 participants. Mean population-level 25(OH)D values varied considerably across the studies (range 4·9-136·2 nmol/l), with 37.3 % of the studies reporting mean values below 50 nmol/l. The highest 25(OH)D values were observed in North America. Although age-related differences were observed in the Asia/ Pacific and Middle East/Africa regions, they were not observed elsewhere and sex-related differences were not observed in any region. Substantial heterogeneity between the studies precluded drawing conclusions on overall vitamin D status at the population level. Exploratory analyses suggested that newborns and institutionalized elderly from several regions worldwide appeared to be at a generally higher risk of exhibiting lower 25(OH)D values. The authors conclude substantial details on worldwide patterns of vitamin D status at the population level and within key subgroups are needed to inform public health policy development to reduce risk for potential health consequences of an inadequate vitamin D status. Br J Nutr. 2013 August. PMID: 23930771
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