Vitamin D Status Tied to Cancers
May 19, 2010
MILAN, Italy—High vitamin D status appears to correlate to reduced risk of several cancers, including colorectal cancer, according to a study published online ahead of print May 6 in the International Journal of Cancer. Scientists from the European Institute of Oncology, Milan, performed a systematic review based on a meta-analysis of observational studies of serum 25-hydroxyvitamin D level and colorectal, breast and prostate cancer, and colonic adenoma.
The team searched the scientific literature through December 2009 considering research reports written in any language. They also performed a meta-regression analysis in order to compute dose-response effects. Also, separate analyses for case-control and prospective studies were performed, as case-control studies usually measure serum 25-hydroxyvitamin D level after the diagnosis of cancer.
In the end, 35 independent studies were indentified. Of these, seven studies on colorectal adenomas were heterogeneous in terms of endpoint and control for major confounding factors; a meta-analysis of these data was not performed. The researchers noted a 10 ng/mL increase in serum 25-hydroxyvitamin D for colorectal cancer (2630 cases in 9 studies); for breast cancer (6175 cases in 10 studies); and for prostate cancer (3956 cases in 11 studies). For breast cancer, case-control studies (3030 cases) had major limitations and obtained summary relative risk (SRR) of 0.83, while SRR of prospective studies (3145 cases) was 0.97. Differences between cases and controls in the season of blood draw or in overweight/obesity or physical inactivity could not explain the results on colorectal and breast cancer. They concluded there was a consistent inverse relationship between serum 25-hydroxyvitamin D levels and colorectal cancer; however, no association was found for breast and prostate cancer.