Using existing data from a large clinical trial, the study zeroed in on women with a history of non-melanoma skin cancer, as people with this generally non-fatal disease are more likely to develop the more lethal illness — melanoma. The researchers found that women who once had non-melanoma and took the calcium-vitamin D combination developed 57 percent fewer melanomas than women with similar histories who were not given the supplements. Non-melanoma skin cancers, such as basal cell or squamous cell cancers, are the most common forms of skin cancer.
"In preventive medicine, we want to target people most at risk for the disease," said dermatologist Jean Tang, MD, PhD, lead author of the study. "If you previously had a non-melanoma skin cancer, calcium plus vitamin D might reduce your risk of the more deadly melanoma."
Tang added a note of caution. The study found that a daily dose of 1,000 mg calcium plus 400 IU of vitamin D doesn't provide skin cancer protection for everybody. Women without a history of non-melanoma skin cancer who took the supplements did not see any reduction of risk compared with their placebo-group counterparts, according to the research.
The study will be published online on June 27 in the Journal of Clinical Oncology.
Vitamin D is well-known for its role in bone growth, but it also affects non-skeletal 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 last November saying that more research was needed on vitamin D and calcium, as the evidence was insufficient to prove their having a benefit for conditions other than bone health.
This study is the second to look at the effect of vitamin D supplementation on cancer risk with a randomized, controlled trial.