NEW YORK (Reuters Health) — Taking 1,000 to 2,000 international units (IU) of vitamin D each day may safely reduce the risk of colorectal cancer, according to pooled data from published studies.The current findings contradict some prior individual studies that found that vitamin D intake did not seem to protect against colorectal cancer. However, it is possible that the dose may simply have been too low to provide a benefit, researchers say.

The present analysis, reported in the American Journal of Preventive Medicine, included data from five studies that looked at the association between blood levels of 25-hydroxy-vitamin D, which provides a good estimate of vitamin D levels in the body, and colorectal cancer risk. Dr. Edward D. Gorham, from the Naval Health Research Center in San Diego, California, and colleagues found that as blood levels of vitamin D rose, the risk of colorectal cancer fell. Risk was reduced by 54 percent in groups with the highest vitamin D levels relative to those with the lowest levels.

In the final analysis, a blood level of 33 nanograms per milliliter (ng/mL) or higher was associated with a 50 percent decreased risk of colorectal cancer relative to a level of 12 ng/mL or lower.