Low levels of vitamin D may be associated with increased total cancer incidence and mortality in men, particularly for cancers of the digestive system, according to a study in the Journal of the National Cancer Institute.
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, M.D., Sc.D., 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.