The tanning industry got another boost recently when an Ivy League professor released his findings on vitamin D and sunlight.

Dr. Edward Giovannucci, professor of medicine and nutrition at Harvard University, gave a lecture recently at a major cancer research meeting, during which he claimed that vitamin D may help prevent 30 cancer deaths for each death from skin cancer--this according to The Associated Press.

UV light would do much more good than harm, then, since sunlight is the best source of vitamin D. By contrast, slathering on sunscreen could possibly lead to a person’s greater risk of cancer than getting calculated doses of UV.

In fact, Giovannucci’s lecture has forced the American Cancer Society to rethink its position on sun protection, the AP says. Other dermatologists are starting to come around as well.

Given this evidence, deciding how much vitamin D--and sunlight--is enough will be a challenge for the medical community.