Times-Union readers want to know:

I saw something on Facebook that says that sunscreen actually causes cancer. Is this true?

An article published in the Journal of Internal Medicine titled “Avoidance of sun exposure is a risk factor for all” was reported by the media in May. The stories said that a study by researchers at the Karolinska Institute in Sweden followed about 30,000 women over 20 years and found that the ones who avoided sunbathing actually had twice the mortality rate of those who had significant exposure to the sun.

Snopes.com reported that the study was summarized by some medical-related websites of dubious validity that ran misleading headlines such as “Scientists Blow the Lid on Cancer and Sunscreen Myth” and asserted that “the link between melanoma and sun exposure is unproven. There’s no conclusive evidence that sunburns lead to cancer. There is no real proof that sunscreens protect against melanoma. There’s no proof that increased exposure to the sun increases the risk of melanoma.”

The study, however, did not prove any such thing.

It is true that the researchers found that at the end of their study period, the women who avoided exposure to the sun had a mortality rate about twice that of women who had the most exposure to the sun. The women were recruited from 1990 to 1992 and ages 25 to 64 at the beginning of the study.

But those results do not prove that, contrary to conventional medical wisdom, high exposure to sunlight and sunburn is beneficial, or that sun exposure isn’t related to skin cancer, or that using sunscreen actually increases the chances of contracting skin cancer.

Health experts maintain that overexposure to ultraviolet radiation from the sun or sunbeds is the main cause of skin cancer.

One of the issues with the study is that the women were light-skinned Caucasians living in areas with low levels of sunshine and a low ultraviolet index. As Snopes.com points out, those women would probably be better off with some sun exposure rather than no sun exposure because the human body needs some sunlight to produce vitamin D, which is essential to good health.

Vitamin D is created in the body through exposure to sunshine and a deficiency is known to increase the risk of diabetes, tuberculosis, multiple sclerosis and rickets, according to medical journals.

Previous studies have shown that vitamin D can increase survival rates for women with breast cancer, while deficiencies can signal prostate cancer in men. Low levels of vitamin D have also been linked to more aggressive forms of skin cancer, according to various reports.

In addition, “those who normally avoid the sun and/or cover most of their skin are advised to take vitamin D supplements,” said Andrea Darling, post-doctoral research fellow from the University of Surrey.

While being printed in a medical journal adds some cache to the study, too many variables in this one makes it very limiting in scope. The American Cancer Society, the Mayo Clinic, the Cleveland Clinic and the Centers for Disease Control and Prevention, along with many other health organizations, agree that too much exposure from the sun or tanning beds can lead to skin cancer.

Carole Fader: (904) 359-4635