In men, low levels of vitamin D appear to be associated with increased cancer incidence and mortality - particularly cancers of the digestive system - researchers report in the April 5th issue of the Journal of the National Cancer Institute.

Co-author of an accompanying editorial, Dr. Gary G. Schwartz of Wake Forest University, Winston-Salem, North Carolina told Reuters Health that “these observations add to a growing body of evidence that vitamin D, whose major source is casual exposure to sunlight, may play important roles in the natural history of many cancers.”

“The idea that sunlight might inhibit the growth of human cancers, proposed by several epidemiologists, and once widely scoffed at,” he concluded, “now appears to be having its rightful day in the sun.”

Dr. Edward Giovannucci who led the research effort told Reuters Health: “Vitamin D deficiency is common and is important to identify and treat for multiple reasons. An increasing body of evidence suggests that a reduction in risk of some cancers may turn out to be another benefit.”

Giovannucci of Harvard School of Public Health, Boston and colleagues note that vitamin D has potent anticancer qualities.

To help quantify its effect, the researchers first correlated determinants of vitamin D exposure with serum levels in some 1000 men. Items involved were dietary and supplementary vitamin D, skin pigmentation, adiposity, geographical residence and leisure-time physical activity, and hence sunlight exposure. The researchers then computed vitamin D levels for 47,800 men in the Health Professionals Follow-Up Study.

From 1986 to 2000, the researchers documented 4286 incident cancers and 2025 cancer deaths in the cohort. These figures excluded organ-confined prostate cancer and non-melanoma skin cancer.

An increment of 25 nmol/L in the predicted blood level of vitamin D was associated with a 17 percent reduction in total cancer incidence, a 29 percent reduction in total cancer mortality and a 45 percent reduction in digestive system cancer mortality.

Total cancer rates in men with the lowest predicted vitamin D level was 758 per 100,000. The rate in those with the highest levels was 674 per 100,000.

For total cancer mortality, the corresponding figures were 326 and 277 per 100,000. For digestive system cancer mortality, the rates were 128 and 78 per 100,000.

SOURCE: Journal of the National Cancer Institute April 5, 2006.