1. Women who spent the most time in the sun outlived those who avoided its rays.
That's according to a recent study that followed almost 30,000 Swedish women for 20 years.
The women who spent the most time in the sun outlived those who avoided the sun by .6 to 2.1 years, on average, mostly due to lower rates of cardiovascular disease and other non-cancer causes of death.
The study authors controlled for factors like smoking, exercise, and obesity, though they only collected some of that information (like that on exercise) midway through the study.
Those who spent most time in the sun did have higher cancer rates, though the authors largely attribute that to the fact that they lived longer.
This was an observational study, so the authors can't say that getting more sun was responsible for longer lives. But they think it's possible that the vitamin D boost people get by spending time in the sun could be a possible explanation for things like improved cardiovascular health.
2. Sunlight wakes you up in the morning and makes it easier for you to fall asleep at night.
Studies of the internal "body clock," or circadian rhythm, show that the best way to adjust to a new time zone is to expose yourself to light at the right time in the morning.
Even if you aren't trying to adjust to a new time zone, this is important because exposure to bright natural light via the sun tells your body that it's daytime, which signals your brain to stop producing melatonin, the hormone that regulates your circadian rhythm. That cue sets your internal clock for the rest of the day, and sets your brain up to start producing melatonin again when you want to go to sleep at night. According to the National Institutes of Health, you'll sleep better if you get an hour of natural light in the morning.
3. Spending mornings in the sun might also help you keep weight off.
Adults who get sunlight early in the day are likely to have a lower body mass index, a measure that takes into account weight and height, according to a recent study.
The fact that people sleep better if they get light in the morning could account for this, since people who get enough sleep have an easier time managing their weight. But even after controlling for sleep time, the association between a lower BMI and morning light was still significant — meaning that the connection between morning sun and staying slim wasn't just due to better sleep.
4. The sun helps people fight off winter depression.
One of the most common and effective treatments for the malaise that sets in during long dark winters is more exposure to natural light. Psychiatrists recommend that people spend more time outdoors getting natural light, and in extreme cases, will also prescribe phototherapy, which is exposure to bright light that mimics the sun.
5. The sun keeps your bones healthy.
That's because your body produces vitamin D when exposed to the sun. The so-called "sunshine vitamin" helps the body absorb calcium, which is essential for bone health. Vitamin D is found in fatty fish like salmon and in fortified dairy products, but it's also naturally produced when the sun shines on skin, triggering a reaction that makes vitamin D from cholesterol.
6. Some research suggests that the "sunshine vitamin" might protect against breast, prostate, and other cancers, as well as heart disease and other illnesses.
Researchers go back and forth on how essential vitamin D is (or isn't) for your health. To try and clarify the issue, two big 2014 studies in the journal BMJ analyzed a large body of existing vitamin D research, taking into account studies on more than a million people.
One study found strong connections between low levels of vitamin D and an increased likelihood of dying from heart disease and cancer, though researchers couldn't say that the low levels caused that increased risk. They also found that the version of the nutrient found in food and produced by the sun was much more effective than the version provided by most supplements.
The other study was more nuanced, finding "suggestive evidence" vitamin D had protective effects, but not finding any clear benefit to vitamin D supplements.
Other researchers have found that vitamin D might protect against breast and prostate cancer.
7. A shockingly large percentage of the population might be vitamin D deficient.
Despite the back and forth over its importance, every cell in the body has a receptor for the sunshine vitamin, according to Michael Holick, a professor and vitamin D expert at Boston University's School of Medicine. Holick estimates that up to one-sixth of the human genome is directly or indirectly regulated by the sunlight vitamin.
Yet, according to the Harvard School of Public Health, as many as a billion people worldwide may be vitamin D deficient, especially those that live north of the latitudinal lines connecting San Francisco to Philadelphia or Athens to Beijing. Vitamin D deficiency can cause bones to become brittle or misshapen, and may have other severe health effects too, though many of those are still under investigation.
Some people have trouble producing enough vitamin D naturally, and the American Academy of Dermatology recommends supplements instead of the sun for skin health.
But some studies also show that supplements don't effectively provide enough vitamin D, and overdoing it with supplements can lead to kidney problems. Your body, meanwhile, won't naturally overproduce it.
Still, you need only about 15 minutes of sun a day to get adequate vitamin D if you are fair skinned — and more if you have darker skin, since melanin, which makes skin darker, makes it harder for your body to take advantage of the sun's rays.
If you are covered up or wearing sunscreen for those 15 minutes, you also won't produce enough vitamin D. People who are older or overweight also have trouble naturally producing enough vitamin D.
