How much sun does your skin need for vitamin D? — Quartz – Quartz
A lot of folks think summer is the perfect time to head outside and soak up all the vitamin D from the sun they couldn’t get during the winter. It’s an essential nutrient that helps our bodies use other substances key to good health, like calcium and phosphorous.
But while it is good to come out of your indoor hibernation, the notion that you have to get vitamin D from the sun is a complete myth. In fact, the official recommendation from the American Academy of Dermatology is that we shouldn’t try to get vitamin D from by seeking out extra rays from the sun. The risk of DNA damage from sun exposure far outweighs the benefits of getting vitamin D—especially when we can just get that compound through food and supplements.
It’s true that sunlight starts a chain reaction that helps our bodies make vitamin D. In addition to visible light, the sun emits radiation in the form of UVA and UVB rays—ultraviolet light wavelengths too short for our eyes to pick up. UVB rays trigger our skin to make a chemical that gets carried by our blood down to the liver, where it becomes vitamin D.
The trouble is, UVB radiation also damages the DNA in our skin cells. Sunburns are actually the body’s immune response to try to repair DNA, as STAT explains. The pink, swollen flesh is the result of a rush of immune cells coming in from dilated blood vessels underneath the burned skin. If the sun’s rays have really screwed up your DNA, your body gives up on the irreparable skin and sheds it entirely, through peeling. The DNA damage that results from lots of UVB exposure over time can also lead to skin cancer.
The benefit of making vitamin D doesn’t outweigh the risk of this DNA damage. Henry Lim, a dermatologist and president of the American Academy of Dermatology, says the organization’s position on vitamin D and sunlight comes in part from a 2014 study that looked at vitamin D blood concentrations and DNA damage in people going on vacations either on the mountains or at the beach. Although the 71 sun-soaking vacationers did have higher levels of vitamin D after six days of vacation, they also had higher levels of a chemical that indicated their bodies were trying to repair genetic damage. The authors conclude that it’s much healthier to get your vitamin D from foods like egg yolks and fish (or fortified milk or orange juice).
“There are no good studies that show any differences [between getting] vitamin D through the skin, through food, or through supplements,” says Lim.
This isn’t to say that you should stay huddled up indoors year-round. “Generally, we all should encourage people to participate in outdoor activities,” Lim says. Hiking, running, swimming, and even just walking around are great ways to get exercise and socialize.
But it’s best to do so with a thick layer of broad-spectrum sunscreen that protect against UVA and UVB rays. Even though UVA rays don’t damage DNA like UVB rays do, they cause wrinkles later in life, Lim says.