Can You Safely Get Vitamin D From the Sun?

1. There’s no one-size sun prescription

Even scientists who endorse sun exposure can’t offer blanket advice on how much to get. That’s because skin tone, location, time of year, time of day, cloud cover, clothing and other factors play roles. In general, the lighter your skin and the closer you are to the equator, the faster you make vitamin D.

Webb says her research in the U.K. — farther north than any U.S. location — suggests that in spring and summer, people with light skin wearing shorts, T-shirts and no sunscreen can get enough vitamin D with 10-15 minutes of midday sun on most days. People with darker skin need 25-40 minutes, she says, because the extra melanin that produces darker skin acts as a “natural sunscreen.”

For light-skinned people, the challenge is remembering to add sunscreen or clothing after a few minutes, she says. For darker-skinned people, the time commitment might be challenging. The payoff for many people, she says, could be storing up enough vitamin D to skip supplements, even in winter, when weak northern sunlight can’t trigger production. 

Studies suggest that people vary greatly in how quickly vitamin D levels in their blood decline, over weeks and months, after effective sun exposure.

2. Sunscreen doesn’t block all vitamin D production … but windows do

Studies show that sunscreen use is not associated with low vitamin D levels, says Henry Lim, M.D., a dermatologist at Henry Ford Health in Detroit and a former president of the American Academy of Dermatology and American Dermatological Association. The likely reason: Most people don’t slather on enough to fully block the ultraviolet B (UVB) rays that trigger vitamin D production, he says. 

Rigorous use of recommended amounts of high-SPF sunscreen (a full ounce — enough to fill a shot glass — applied at least 15 minutes before heading outside) and other sun-protection measures could substantially limit vitamin D production, he acknowledges. But, Lim says, most people who spend time outside get at least a little vitamin D, even if they generally follow sun safety advice. FYI: You won’t make any vitamin D sitting in front of a window. The UVB rays don’t get through the glass.

3. Sun damage is cumulative

Dermatologists who frown on unprotected sun exposure stress that the damage that can lead to skin cancer is cumulative. “Small amounts do add up,” says Elizabeth Hale, M.D., a clinical associate professor of dermatology at NYU Langone Medical Center and senior vice president of the nonprofit Skin Cancer Foundation.

Cumulative sun exposure is closely associated with the most common skin cancers, basal cell carcinoma and squamous cell carcinoma, Lim says. Those cancers can be disfiguring or cause other problems if not caught and removed early.

The link between lifetime sun exposure and melanoma, a more deadly skin cancer, is not as clear, Lim says. But, he says, in light-skinned people, melanoma is clearly linked with multiple sunburns.

In the U.S., the lifetime risk for skin cancer is about 1 in 5; the risk of melanoma is 1 in 27 for men and 1 in 40 for women, according to the American Academy of Dermatology.

Cancer isn’t the only concern: Cumulative sun damage causes wrinkles, spotting, sagging and other signs of skin aging, dermatologists say.

4. Supplements are quite safe

Manson is the lead researcher on a study of nearly 26,000 healthy older adults, half of whom took 2,000 IU vitamin D supplements for an average of 5.3 years. “There were no appreciable side effects,” she says. Though findings on benefits have been mixed (see box), the supplements are so safe that people should feel comfortable taking 1,000 IU to 2,000 IU of vitamin D daily “as a form of insurance,” she says. People with some conditions might need higher doses but should take them under medical supervision, she says.  

Multivitamins with 1,000 IU of vitamin D are a cheap, easy way to get enough, Lim says.

5. Indoor tanning is always a bad idea

Indoor tanning lights raise skin cancer risks without boosting vitamin D because they contain too little UVB, Lim and Hale say. “Indoor tanning is directly carcinogenic,” Hale says.

6. No one wants you to be a hermit

Pittas says too many people “are afraid of the sun” and lead sedentary indoor lifestyles.

No one is in favor of that. “I strongly encourage everyone, especially older adults, to have regular physical activity and to spend time outdoors,” Manson says. “I think that's extremely important for good heart health, cognition and emotional well-being.” Wearing sunscreen doesn’t diminish those benefits, she says.