Host of Health Benefits Attributed to Sunlight

But to avoid skin cancer, you have to be careful not to get too much.

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The fiery ball of radiation that climbs into the sky every morning can be just as good for your health as it is damaging. In fact, some experts now believe that the sun's rays provide more benefit than harm—provided you get the right dose.

Even dermatologists, who worry about the sun's ravaging effects on the skin in the form of cancer, age spots, and wrinkles, acknowledge that we could all use a little sun exposure. "Being out in the sun boosts our mood, improves sleep, and promotes vitamin D production," says James Spencer, associate clinical professor of dermatology at Mt. Sinai School of Medicine in New York. "There's no controversy about that." Still, he emphasizes, the operative word is little when it comes to exposure. "The majority of people aren't putting on sunscreen every time they step outside, and that 5 or 10 minutes a day of casual exposure is probably all you need." Much attention has been paid to the benefits of vitamin D, which is manufactured when the sun's UV-B rays hit the skin and which protects against cancer, bone brittleness, heart disease, and a host of other ills. But there are other payoffs to a small daily dose of sunlight, including:

• Better sleep. Natural daylight helps shut off your body's production of melatonin, a hormone produced at night that makes you drowsy. This can help you maintain a normal circadian rhythm, so you're more likely to feel tired at bedtime when it's dark outside. Going outside for 15 minutes at the same time each day, preferably in the morning, gives your body a clear signal that it's no longer night. Also, forgo the sunglasses if possible, since this will enable sunlight to pass unhindered through your eyes to the brain's pineal gland, triggering the gland to stop releasing melatonin.

• Happier outlook. A type of depression called seasonal affective disorder affects some people during the winter when they don't get enough sunlight. Experts now believe that sunlight has widespread mood-elevating effects, possibly because the "happy" hormone serotonin increases when nights are short and days are long. In fact, psychiatrists often recommend that depressed individuals go outside in the sun for 30 minutes a day. Bonus: You can slather on all the sunscreen you want and still reap the mood benefit.

• Protection from autoimmune diseases. Exposure to UV radiation appears to suppress an overactive immune system, according to an April report published in Environmental Health Perspectives. This could explain why exposure to UV rays may help with autoimmune diseases like psoriasis and lupus; one recent study also suggests it might help alleviate asthma.

• Lessening of Alzheimer's symptoms. Elderly Alzheimer's patients exposed to bright lighting during the day—from 9 a.m. to 6 p.m.—got better scores on a mental exam, had fewer symptoms of depression, and lost less function than did those exposed to dim daytime lighting, according to a study published this month in the Journal of the American Medical Association. The researchers attributed the improvement to more-regular circadian rhythms, which are thrown out of whack when advanced dementia sets in.

Coming next: To tan or not to tan? A look at the controversy