Q: I’ve heard two conflicting things about sun exposure — that you should avoid it and that it’s good for you. What should I believe?
For decades, many doctors have said that less is more when it comes to sun exposure. Ultraviolet light from the sun can age the skin and cause skin cancer, and people can get vitamin D from food or supplements instead.
But in recent years, some scientists have questioned this thinking after research suggested that moderate sun exposure may, at least in certain contexts, have some benefits. And that vitamin D supplements may not always be a good substitute.
“The ‘never go outside without S.P.F. 50’ approach treated sun exposure as if it were universally harmful,” said Dr. Lucy McBride, an internal medicine physician in Washington, D.C. But “moderate, thoughtful sun exposure,” in accordance with your risk factors, she added, “may offer benefits we’re still discovering.”
Sunshine has a bright side.
It’s undeniable that the sun’s rays can damage your skin in ways that result in premature skin aging and cancer, said Dr. Elizabeth Ko, an internal medicine physician at UCLA Health who has written about the health effects of sun exposure.
But researchers have also identified a handful of potential, if limited, associations between sun exposure and health benefits.
Research has found that spending more time in the sun is associated with lower blood pressure. Blood pressure tends to be higher in the winter than in the summer, said Dr. Richard Weller, a dermatologist and researcher at the University of Edinburgh, and heart problems are more common then, too. One study found that people who reported more sunlight exposure were less likely to develop heart failure.
Researchers aren’t sure why sunlight might improve heart health, but they do know that it causes the skin to release a gas called nitric oxide, which relaxes blood vessels and reduces blood pressure, Dr. Weller said.
Some researchers have wondered if that could result in a longer life. In a 2014 study that followed nearly 30,000 Swedish women for 20 years, scientists found that those who avoided the sun were twice as likely to die during that time period as those most exposed to sunlight — even though the sun-seeking women were more likely to be diagnosed with melanoma, a deadly form of skin cancer.
Sunlight may also help support the immune system by controlling inflammation and immune cells. In one small study of 11 multiple sclerosis patients, researchers found that ultraviolet B light activated certain immune cells that calmed inflammation and eased symptoms. Other research has shown that UV light exposure can improve symptoms in people with eczema, psoriasis and other immune-related conditions, Dr. McBride said.
Basking in the sun could also make you happier, Dr. Ko added. Some studies suggest that exposure to UV light can increase blood levels of serotonin, a chemical that helps regulate mood.
Of course, it’s hard to to tell if the sunlight itself is responsible for these health benefits, Dr. McBride said. People who are exposed to a lot of sunlight may also engage in more physical activity and spend more time in nature than other people do, she said, all of which may independently boost mood and physical health.
It may not (just) be the vitamin D.
A well-known benefit of sun exposure is that it triggers the body to produce vitamin D, which helps to build and maintain bones. Past observational research has linked low levels of vitamin D with increased risks of certain conditions like heart disease, Type 2 diabetes and colorectal cancer.
Would ingesting vitamin D from fortified foods or supplements reduce the risk of these conditions, eliminating the need for potentially harmful sun exposure? Large clinical trials over the past several years have not confirmed this, Dr. Weller said.
In a 2019 clinical trial, researchers concluded that taking vitamin D supplements did not reduce the likelihood of developing Type 2 diabetes in about 2,400 adults who had risk factors for the condition. And a 2020 trial of about 26,000 adults in the United States found that vitamin D supplements did not reduce the risk of developing cancer or cardiovascular problems, nor did it reduce the overall risk of death over the study period, which averaged about five years.
These studies, along with those showing the immune and blood pressure benefits of sunshine, suggest that sunlight may benefit us beyond just vitamin D production, Dr. McBride said.
Don’t ditch your sunscreen.
The research on sunshine’s potential benefits is still quite limited, so it’s hard to know how to interpret or apply it, or how to square it with the risks for skin cancer, Dr. McBride said. And you shouldn’t stop using sun protection altogether, she said.
Dr. Ko recommended avoiding direct sun exposure between 10 a.m. and 2 p.m., “when the rays are the brightest and strongest.” If you can’t do that, wear sunscreen or other protection such as wide-brimmed hats or sun-protective clothing.
Ultimately, it may make sense to consider sunlight’s potential benefits along with its harms, Dr. McBride said.
“Skin cancer remains a serious threat,” she said. “But it is about moving beyond fear-based, one-size-fits-all messaging.”
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