The pros and cons of sun exposure don’t start and end with vitamin D and skin cancer
twas around 15 years ago that Dr. Matt Zirwas, an Ohio-based dermatologist, first noticed something curious about the people he was treating at his clinic.
“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.
When most people consider UV light and its effects, skin cancer and premature aging come to mind. And there’s no question that exposure to the sun, tanning beds, and other sources of UV light damages the skin in ways that promote aging and cancer. That’s why most dermatologists and public health officials recommend that Americans slather sunscreen on exposed skin whenever they leave the house — even in the wintertime — or take other steps to avoid sun exposure.
“The standard line from dermatologists is that no part of your skin should ever be exposed to unprotected sun,” Zirwas says. “And I agree that if you’re talking about preventing skin cancer and aging, you want to avoid the sun.” But his clinical observations made him wonder whether the story on UV light was really all negative, and if a zero-tolerance policy on sun exposure was warranted when taking a broad view of human health.
“We evolved as outdoor creatures who were exposed to the sun, so it never made sense to me that sun exposure would be all bad,” he says.
Zirwas started reading the published literature on UV exposure and human health. 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 data included questionnaires that asked women about their sun habits, as well as about their smoking history, alcohol use, body weight, education level, income, and other variables that tend to raise or lower a person’s risk for death.
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.”
“That study,” he adds, “made me say, ‘Oh my God, there has to be a lot more to this story.’”
A case for sun exposure?
Heart disease is the most common cause of death in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC). And that study from Sweden found that a drop in heart-disease deaths among the sun-exposed women was the most significant contributor to their lower mortality rates.