If you needed four more reasons to take advantage of sunny days, we have you covered.
woman in sunshine
Credit: Getty Images/Lilly Roadstones

You probably know that catching a few rays can help your body produce vitamin D, a key nutrient for bone and heart health that 42% of American adults are deficient in. But it also sparks some other pretty impressive—and surprising—health benefits.

Better Sleep and Mood

"Light is the most powerful signal for the brain and internal body clock, helping to regulate sleep and wake activity, appetite, mood, alertness and attention," says Phyllis Zee, M.D., Ph.D., a neurologist and sleep specialist at Northwestern University in Chicago. Research she published in the Journal of Clinical Sleep Medicine found that workers who got more light during the day—by sitting near a window, not from actually being in the sun—averaged 46 more minutes of sleep on work nights (and almost 2 hours more on free nights) than those who toiled in darker environments. Studies have also shown that when sunlight hits your skin, it stimulates the production of serotonin, a feel-good hormone linked to improved mood, energy and alertness and to less depression and anxiety.

Lower BMI

Zee's research also suggests that getting sunlight early in the day may make it easier to maintain a healthy weight. (Again, we're talking light exposure, not necessarily direct sun exposure.) Compared with afternoon and evening rays, she says, "morning light contains bright, short-wavelength blue light that has the strongest effect on synchronizing your circadian rhythms, which control hormones and chemicals that regulate appetite and metabolism." In Zee's study, people who got plenty of a.m. light had lower body mass indexes—an average of 25—while others exhibited more than a 1-point uptick in BMI for each hour of light exposure later in the day. To harness the benefits, she suggests opening your shades when you wake up and aiming for at least 20 to 30 minutes throughout the morning and early afternoon.

Reduced Multiple Sclerosis Risk

People living in sunnier areas of the world are less likely to develop this chronic condition, which causes the immune system to attack the body's own central nervous system, according to a study published in Neurology. Even moderate UVB exposure— between 4 and 10 hours a week—was shown to lower the risk of MS in women under 40 by as much as 65%, compared to those in less sun-drenched areas. (Although being outdoors, particularly during the summer months, can be beneficial no matter where you reside.) The researchers believe the reason may be related to sunlight's effect on vitamin D levels, since deficiency in this nutrient has been linked to an increased risk of developing MS. But it may also have to do with sunlight itself and its direct effect on the immune system.

Better Blood Pressure Control

A new study published in the Journal of the American Heart Association analyzed more than 45 million blood pressure measurements that were recorded over the course of three years and uncovered a clear pattern of lower systolic blood pressure—the top number on a blood pressure reading—during summer compared to winter. This effect was independent of outdoor temperature, and the researchers think UV rays are the X-factor. Sunlight may increase levels of nitric oxide, a molecule that helps blood vessels dilate, which in turn lowers blood pressure. Still, JoAnn Manson, M.D., Dr.P.H., chief of preventive medicine at Boston's Brigham and Women's Hospital and a professor of medicine at Harvard University, says more research is needed, and that the best treatment remains a healthy, low-sodium diet and medication.

This story originally appeared in EatingWell Magazine July/August 2020.