Abstract
OBJECTIVE
There is increasing interest in vitamin D and its possible health effects. The aims of the present overview are to summarise the research on common diseases for which there is substantial evidence on vitamin D, identify diseases where vitamin D may be beneficial and discuss the public health implications of these findings.
DESIGN
Literature search of PubMed for the years 2000 to 2010 to identify cohort studies with baseline measures of 25-hydroxyvitamin D (25(OH)D) and randomised controlled trials (RCT) of vitamin D supplementation in relation to fractures, colorectal cancer, CVD and all-cause mortality. Risk ratios of disease from comparisons between 25(OH)D quantiles in these studies were summarised using RevMan software version 5·1 (The Nordic Cochrane Centre, Copenhagen).
SETTING
Community-based samples recruited into cohort studies from many countries.
SUBJECTS
Older men and women, mostly above 50 years of age.
RESULTS
When comparing the lowest 25(OH)D category with the highest (or reference), the pooled risk ratio (95 % CI) was: 1·34 (1·13, 1·59) for fractures from nine studies; 1·59 (1·30, 1·95) for colorectal cancer from nine studies; 1·35 (1·17, 1·56) for CVD from twelve studies; and 1·42 (1·23, 1·63) for all-cause mortality from twelve studies.
CONCLUSIONS
Cohort studies show that baseline 25(OH)D levels predict increased risk of fractures, colorectal cancer, CVD and all-cause mortality. These associations are weak and could be explained by confounding variables such as obesity and physical activity. Because of their potential public health significance, RCT using vitamin D doses ≥50 μg/d are required to determine whether vitamin D protects against these diseases.
Collapse