Vitamin D intake may cut risk of colorectal cancer

NEW YORK (Reuters Health) -- Intake of 1000 to 2000 IU of vitamin D each day may safely reduce the risk of colorectal cancer, according to the results of a meta-analysis of published data.

The current findings contradict what was seen in previous studies, such as the Women's Health Initiative. In those trials, 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.

The present analysis, reported in the American Journal of Preventive Medicine for March, included data from five studies, identified through PubMed, that examined the association between serum 25(OH)D levels and colorectal cancer risk.

As serum levels of 25(OH)D rose, the risk of colorectal cancer fell, lead author Dr. Edward D. Gorham, from the Naval Health Research Center in San Diego, California, and colleagues note. Compared with the lowest serum level quintile (median 12 ng/mL), the highest quintile (median 37 ng/mL) cut the risk by 54% (p < 0.0001 for trend).

On the final pooled analysis, a serum 25(OH)D level of 33 ng/mL or higher was associated with a 50% decreased risk of colorectal cancer relative to a level of 12 ng/mL or lower.

The researchers believe that the target serum levels could be achieved with intake of 1000 to 2000 IU of vitamin D per day. Moreover, they note that the National Academy of Sciences has established that a dose of 2000 IU/day is safe.