“The older patients I was seeing [who had] lots of sun damage and lots of skin cancer would be very robust, very energetic people,” he says. These were people who, apart from their skin cancers, tended to be in excellent health and taking very few prescription drugs.

“But then I’d see these people who had beautiful skin and no cancers, and they were very low-energy and taking medications for all these different health problems,” he recalls. He began to wonder whether exposure to ultraviolet (UV) light, mostly from the sun, had more health benefits than he and other experts realized. //

In 2014, a study appeared that Zirwas says changed his thinking from “this is all kind of interesting” to “holy shit!”

That study was published in the Journal of Internal Medicine, and it examined 20 years of health data collected from nearly 30,000 Swedish women. //

The study found that the risk of death from all causes approximately doubled among women who tended to avoid the sun compared to women who got the greatest amount of UV exposure — including from both the sun and from tanning beds. The relationship was dose-dependent, the study found, meaning that the more sun a woman reported getting, the lower her risk of death. The protective effect of sun exposure remained significant, even after the study authors adjusted their figures for income, BMI, smoking history, and other factors that could account for their findings. //

“If that study’s findings are correct,” Zirwas says, “that means protecting yourself from ultraviolet light could have the same effect on your mortality as deciding to smoke a pack of cigarettes a day.” //

Even if sun exposure were the sole cause of all skin cancers, which is unlikely, the lethality of the disease is far lower than one might assume. The American Academy of Dermatology estimates that melanoma will kill 7,230 people in the United States this year, while other forms of skin cancer will claim another 4,420 lives. Cardiovascular disease, meanwhile, kills approximately 650,000 Americans each year, per the CDC. Both Zirwas and Weller argue that if sun exposure offers even modest protection against heart disease, the benefits of sun exposure could quickly outweigh its risks. //

But short of burning, he says [Zirwas] has no problem with people developing a tan — a position that would likely outrage many of his fellow dermatologists. “I think the benefits of [non-burning] sun exposure far outweigh the skin-cancer risks,” he says.