How could skin cancer be associated with a reduced risk of death? A dig through the skin cancer stats yields some surprises.

Skin cancer is by far the most common type of cancer in the United States, according to the CDC. And for those who develop melanoma, skin cancer is serious and sometimes lethal. But the vast majority of skin cancers — roughly 99% — are non-melanoma basal cell and squamous cell cancers. Of these, roughly 80% are basal cell cancers (BCCs). While removing BCCs can be a painful procedure and one that results in significant scarring, these cancers are almost never deadly. These are also the skin cancers most closely associated with sun exposure, and that commonly show up on a person’s hands, scalp, and other sun-exposed areas, according to the American Cancer Society (ACS).

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.

Heart experts say this argument has some merit. “The idea that sunlight is good for our hearts makes a lot of sense,” says Dr. James O’Keefe, a cardiologist at Saint Luke’s Mid America Heart Institute in Kansas City, Missouri. Studies have shown that exposing skin to UV light triggers the release of nitric oxide in the blood, which results in a drop in blood pressure. “Nitric oxide keeps vessels soft and supple, and it gives them a Teflon-like surface so platelets don’t stick,” O’Keefe says. “And when skin is exposed to sunlight, nitric oxide is released into the bloodstream in pretty large amounts.”

Monica, 34, wears sunscreen on her face, and Tony, 52, no sunscreen; Sayulita, Mexico. Photo by Jillian Mitchell

UV exposure could benefit the heart in other ways. “Sunlight leads to the release of the chemical serotonin, whose effects include expansion of blood vessels that, in turn, can help to reduce blood pressure,” says Dr. Michael Miller, director of the Center for Preventive Cardiology at the University of Maryland School of Medicine. Miller says he recommends that the people he sees get 10 to 15 minutes of daily sun exposure.

“One thing that is astounding about modern life is that most of us spend most of our time indoors, and when we go outside, many of us protect ourselves against the sun,” says Nina Jablonski, a biological anthropologist at Penn State University. This is vastly different from the way human beings lived even 100 years ago, when many people worked in farming or other predominantly outdoor occupations. “So the combination of these things — our indoor lifestyle and taking some precautions against sun exposure — means many of us have almost zero sun exposure and zero ability to make vitamin D through our skin.”

Jablonski says every human being’s skin has adapted to the type of sun exposure their ancestors endured. This adaptation — calibrated to specific latitudes and levels of ultraviolet radiation — offered their ancestors protection from sun damage while allowing in enough UV light to facilitate vitamin D production and other important biological processes.

While people of Northern European ancestry who have pale skin tend to suffer from high rates of skin damage and skin cancer if they live in places near the equator, Hispanics and people of African ancestry who move into more temperate regions may suffer due to the lack of sun exposure, she says. Some researchers have even postulated that low vitamin D levels among African Americans could help explain in part why, in America, they are more likely than white people to die from heart disease, stroke, diabetes, and some cancers.

“I think dermatologists want people to have skin that is healthy and cancer-free for as long as possible,” Jablonski says. “But most aren’t looking past the skin — they’re not thinking about the global well-being of their patients.” While she doesn’t believe that taking a vitamin D supplement can fully replace the health benefits of sun exposure, she says it’s one measure that research has linked with improved health outcomes.

But others disagree with her on this point. “Everyone gets utterly fixated on vitamin D, but when you give people vitamin D supplements, the only thing that has been shown categorically is that it’s good for bone health,” says the University of Edinburgh’s Weller.

His take is largely supported by the recently completed VITAL trial, which measured the effect of long-term vitamin D supplementation on the health outcomes of more than 25,000 American adults. That trial found that people who took a daily 2000-IU vitamin D supplement for five years did not experience a significantly reduced risk for heart attack, stroke, or death due to cardiovascular disease or all causes.

“The randomized controlled trials on vitamin D supplementation have generally been disappointing,” says Dr. JoAnn Manson, who led the VITAL trial and is chief of the Division of Preventive Medicine at Brigham and Women’s Hospital in Boston. Manson is quick to note that vitamin D is very important to heart health. It’s just that people don’t need much of it, and very few Americans are so deficient in vitamin D that their heart health is suffering for it, she says.

Weller argues that Vitamin D is just a marker for sun exposure, and that many of the studies linking low vitamin D status to poor health outcomes are really evidence that a lack of adequate sun exposure is harmful to human health. “People assume that vitamin D is responsible for all the benefits of sunshine, and the standard advice from dermatologists is all about avoiding sunshine and taking a vitamin D supplement,” he says. “But there are probably lots of pathways by which sunlight exerts beneficial effects.”