Let the sunshine in. It’s good for the heart, according to a new study.

It’s no excuse to start sunbathing for hours without sunscreen, to be sure, but the new research suggests that avoiding the sun might shorten your life.


Back in the early 1990s, nearly 30,000 Swedish women filled out a questionnaire about how often they spent time in the sun in the summer or went to sunny climes for holiday in the winter. Over the next 20 years, researchers reported a few years ago, those who had the most sun exposure, compared with those with the least, were half as likely to die from all causes.

In the latest study, the researchers determined that the reason the sun seekers were less likely to die earlier was an decreased incidence of cardiovascular disease, which can cause death from heart attacks and stroke.

The sun seekers did have a greater prevalence of cancers, both skin cancers and internal cancers. But that’s most likely because they lived longer. Age is one of the strongest risk factors for cancer. Interestingly, those who had nonmelanoma skin cancers, such as squamous or basal cell cancer, which are rarely fatal, tended to have been exposed to the most sun—and had the lowest rates of overall mortality.

How much longer did sun seekers live? Depending on other risk factors, such as smoking, sun seekers lived between six months and two years longer than sun avoiders, on average.

To put this study in perspective, we spoke with Michael F. Holick, PhD, MD, professor of medicine, physiology and biophysics at Boston University School of Medicine, an expert on vitamin D. He cautioned that this is an observational study, so it doesn’t prove cause-and-effect relationships, but noted that it fits in with other research—in both men and women.


Vitamin D, which the body produces in response to sun exposure, is of course a likely protective factor. In the famous Framingham Heart Study, men and women with blood levels of vitamin D below 15 ng/mL were 50% more likely to have a heart attack than those with higher levels. For reference, the Endocrine Society recommends blood levels at or above 30 ng/mL.

Vitamin D is heart-healthy in many ways—it helps regulate blood pressure (by tamping down production of the pressure-raising protein renin), improves the functioning of blood vessels (by reducing production of “foam” cells that can lead to atherosclerosis) and helps strengthen the heart muscle itself.

But the sun also stimulates the skin to produce nitric oxide, which is then released into the bloodstream, noted Dr. Holick. “Nitric oxide allows our blood vessels to relax, and that can reduce blood pressure.” Sun exposure also promotes production and release of feel-good beta endorphins—one reason that sunny days may be mood boosters—which reduces stress, protecting the heart.


Before you head out unprotected into the sunshine, remember that Swedes (the subjects of the latest research) are much more likely to suffer a sun drought than most Americans. Stockholm, for example, gets only about 1,800 hours of sunshine a year—compared with 3,200 hours in, for example, Grand Junction, Colorado.

Most Americans can get enough vitamin D in the summer by receiving sensible sun exposure, Dr. Holick explains in the Bottom Line article “The Truth About Sunshine,” which includes many tips on balancing sun exposure and sun protection. He has also developed a free app called dminder (available for Android and Apple) that lets you personalize optimal sun exposure.

To ensure adequate vitamin D all year round, he recommends a supplement—for children, 600 IU to 1,000 IU daily…for most adults 2,000 IU daily…and for obese adults 4,000 IU to 6,000 IU daily. That’s because anyone living north of Atlanta can’t make enough vitamin D from sun alone between October and April. For the record, vitamin D-2 is just as effective as vitamin D-3, so it doesn’t matter which form of the supplement you take.