Low levels of vitamin D may be associated with increased total cancer incidence and mortality in men, particularly for cancers of the digestive system.

Previous studies have suggested that sunlight exposure and increased vitamin D intake is associated with a reduced risk of certain cancers, particularly cancers involving the digestive system.
Thirty minutes of sunlight exposure for a person with light skin can produce approximately 20,000 IU of vitamin D.
Recent studies have suggested daily intake of vitamin D should be increased from 400 IU to 1000 IU.

Edward Giovannucci, of Harvard School of Public Health, and colleagues examined vitamin D exposure and cancer incidence for 47,800 men in the Health Professionals Follow-Up Study cohort.
Between 1986 and January 31, 2000, the authors documented 4286 cases of cancer, and 2025 cancer deaths.
They estimated vitamin D levels by recording each man's dietary intake and supplementation, skin pigmentation, adiposity, geographic residence, and leisure-time physical activity.

The authors observed that an increase in estimated vitamin D levels equivalent to 1500 IU of vitamin D daily, was associated with a 17% reduction in total cancer incidence, 29% reduction in total cancer mortality, and 43% and 45% reduction in incidence and mortality from digestive system cancers.

Among men with the lowest vitamin D exposure, there were 758 cases of cancer diagnosed per 100,000 men and 326 cancer deaths per 100,000 annually.

Among men with the highest vitamin D exposure, there were 674 cancers diagnosed per 100,000 men and 272 cancer deaths per 100,000.

The authors suggest that low levels of vitamin D may be associated with increased cancer risk, and they suggest that daily supplementation with at least 1500 IU of vitamin D may be required to optimize benefits on cancer risk.

The authors write, " confirming that vitamin D levels indeed account for the associations we observed is critical because current health recommendations typically discourage high intake of vitamin D and high levels of sun exposure, at least without use of sunscreen, which effectively blocks vitamin D production."

In an accompanying editorial, Gary G. Schwartz, of Wake Forest University in Winston-Salem, and William J. Blot, of the International Epidemiology Institute in Rockville, compliment the findings of Giovannucci and colleagues and suggest the findings support past epidemiologic observations. They write, " The promising results from both observational and laboratory studies should usher in a new era of intervention studies of vitamin D and cancer risk. Because many public health scientists are already clamoring for higher levels of vitamin D supplementation for bone and other health, randomized trials of vitamin D and cancer risk should be undertaken speedily. If the promise of vitamin D holds, a brief walk in the sun may turn out to be a step toward cancer prevention."

Source: Journal of the National Cancer Institute, 2006


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