Vitamin D is associated with a lower risk of cancer

A daily dose of 1000 IU of vitamin D could reduce the incidence and mortality associated with colon, breast, prostate, and ovarian cancer, an extensive review says.

The review searched PubMed in December 2004 for epidemiological studies looking at the association between cancer and vitamin D, sunlight, ultraviolet radiation, and latitude. The study, which was published online in the American Journal of Public Health on 27 December (www.ajph.org, doi:10.2105/AJPH.2004.045260), found 63 observational studies, and of these 30 looked at colon cancer, 13 at breast cancer, 26 at prostate cancer, and seven at ovarian cancer. Most studies found that a sufficient intake of vitamin D protected against cancer.

The researchers, led by Cedric Garland, from the University of California at San Diego, said: “The evidence suggests that efforts to improve vitamin D status, for example by vitamin D supplementation, could reduce cancer incidence and mortality at low cost, with few or no adverse effects.” They say that the high prevalence of vitamin D deficiency in the United States and the discovery that people who are deficient in the vitamin have a higher risk of certain types of cancer may mean that vitamin D deficiency accounts for several thousand premature deaths from colon, breast, ovarian, and prostate cancer each year.

More than 1000 laboratory and epidemiological studies have been published concerning the relationship between cancer and vitamin D and its metabolites, the authors found. Long term studies have shown the effectiveness of vitamin D in reducing the risk of cancer risk and, when administered with calcium, in reducing the incidence of fractures. “Despite these reassuring studies, the public health and medical communities have not adopted use of vitamin D for cancer prevention,” they said.

The review warned that the prevalence of vitamin D deficiency is high in all races in the US, even in temperate areas, but is particularly high among black Americans. It said a recent study found that 42% of black women had seriously deficient concentrations (<15 ng/ml) levels of the main form of circulating vitamin D, 25-OH vitamin D. The concentrations of this form of vitamin D in black people are about half those in white people, the review found, and in northern cities with large black populations mortality from colon cancer is substantially higher among black than among white people.

The US National Academy of Sciences currently recommends a daily intake of vitamin D of 200 IU for people younger than 50, 400 IU for people aged 51-70, and 600 IU for those older than 71. Intake of vitamin D of up to 1000 IU a day would maintain serum 25-OH vitamin D concentrations at or above 30 ng/ml in most people and is unlikely to produce toxicity, the authors said. The national academy's Institute of Medicine considers 2000 IU a day as the safe upper limit, but typical recommended intakes are far below this.