Vitamin D plus calcium may have a skin cancer-reducing effect in women

Women at high risk of developing melanoma who take supplements of vitamin D and calcium may be at a reduced risk of developing skin cancer, suggests new US study.

The study used data from a randomized controlled trial involving 36,282 postmenopausal women (aged 50 to 79) who received either a placebo or 400 IU of vitamin D and 1,000 milligrams of calcium carbonate per day for an average of seven years (1). The analysis focused on the melanoma risk of women with a history of non-melanoma skin cancer. The study results indicated that women who once had non-melanoma skin cancers and took the calcium-vitamin D combination developed 57 percent fewer melanomas than women with similar histories receiving the placebo. Women without a history of non-melanoma skin cancer who took the supplements did not see any reduction of risk compared with the placebo group.

The researchers commented that the results should be interpreted with caution but the findings would prompt more studies. As men were not included in the trial, the researchers cannot be certain whether the protective effect of the supplements would also apply to men with a history of non-melanoma skin cancer. The scientists noted that the lack of protective effect in women without a history of non-melanoma skin cancer may be due to the very low dose of vitamin D, based on today's knowledge, given to the patients in the trial.

Non-melanoma skin cancers, such as basal cell cancer, are the most common forms of skin cancer. People with this generally non-fatal disease are more likely to develop the more lethal illness, melanoma. Vitamin D is well-known for its role in bone growth, but it also affects nonskeletal cells. In many parts of the body, including the skin, vitamin D controls how quickly cells replicate, a process that often goes awry in cancer. Reports from various institutions have suggested that vitamin D is associated with lower risks of colon, breast, prostate and other cancers. Nonetheless, the Institute of Medicine published a report in November 2010 saying that more research was needed on vitamin D and calcium, as the evidence was insufficient to prove their benefit for conditions other than bone health.

1. Tang J. Y. et al. Calcium Plus Vitamin D Supplementation and the Risk of Nonmelanoma and Melanoma Skin Cancer: Post Hoc Analyses of the Women's Health Initiative Randomized Controlled Trial. Journal of Clinical Oncology. 2011.