Vitamin D may decrease colon cancer risk

High blood levels of vitamin D are associated with a reduced risk of colorectal cancer, according to a new French analysis.

The meta-analysis included data from 35 epidemiological studies on vitamin D blood levels and the risk of colorectal, breast and prostate cancer to assess whether vitamin D status – measured as 25(OH)D level – is a risk factor or a risk marker for cancer (1). The analysis showed that for every 10 nanograms per milliliter increase in 25(OH)D levels, the associated risk of colorectal cancer decreased by 15 percent. On the other hand, no association was observed between vitamin D levels and the risk of breast or prostate cancer.

The researchers commented that additional observational studies of vitamin D and cancer should adopt different designs, such as assessment of serum 25-hydroxyvitamin D in colorectal blood at different points in time or longer follow-ups of subjects. To test whether increasing the 25-hydroxyvitamin D level changes the risk of colorectal cancer and to determine how much of an increase is required to change the risk of cancer sufficiently, they concluded that new randomized controlled trials need to be conducted. To date, there have been numerous studies suggesting associations between vitamin D and lower risks of certain cancers while also showing that the relationship between vitamin D and cancer is ambiguous as it depends on the type of cancer.

1. Gandini S. et al. Meta-analysis of observational studies of serum 25-hydroxyvitamin D levels and colorectal, breast and prostate cancer and colorectal adenoma. International Journal of Cancer. 2011; 128(6):1414–1424.