Vitamin D: Study shows intake does not affect melanoma risk

Key Points

San Francisco - Intake of vitamin D does not affect the risk of developing melanoma, according to a recent study.

"The amount of vitamin D that you consume (in diet) and that you take in supplements does not influence your risk of melanoma, based on this study," says Maryam Asgari, M.D., M.P.H., a research scientist at Kaiser Permanente Northern California, Oakland, Calif., and a clinical assistant professor at the University of California, San Francisco.

The study involved more than 68,000 participants who were followed prospectively for up to five years. It minimized recall bias through its design, according to Dr. Asgari. The study subjects were aged 50 through 76, with slightly more males than females, recruited between 2000 and 2002.

Investigators assessed melanoma risk factors such as education, gender, family history, hair color, presence of freckles at a younger age, whether or not they had moles removed and if they had any non-melanoma skin cancers. Investigators did not perform nevus counts.

Researchers excluded subjects who had a melanoma diagnosis at baseline or had pre-existing conditions that might modify vitamin D synthesis, including a history of cirrhosis of the liver, chronic liver disease or history of kidney disease.

One of the strengths of the study is that the sample population was recruited in western Washington, a geographic location that limits the impact of sunshine on vitamin D levels. Investigators did not measure sun exposure, Dr. Asgari says, adding that investigators did not collect serum vitamin D levels from patients.

"We are pretty sure that dietary intake and supplements will be reflective of total vitamin D status," she says.

Investigators found 455 incident melanomas through linking to the Surveillance, Epidemiology and End Results (SEER) cancer registry. They did not find a risk reduction of melanoma in the highest quartiles of vitamin D intake through diet (RR=1.31, CI=0.94-1.82), 10-year average supplemental vitamin D intake (RR=1.13, CI=0.89-1.43), or the combination of diet and supplements (RR=1.05, CI=0.79-1.40).

Interestingly, investigators observed that increased intake of vitamin D through diet alone resulted in elevated risk of developing melanoma, Dr. Asgari says.

"The more they consumed from their diet, the more increased risk they had," she says. "When you combined diet with a supplement, however, which is total value, we did not see an increased risk of melanoma," Dr. Asgari says.