Feeling SAD? How Sunlight Affects Health
Find out why it's important to light up your life during the winter months
Carol Torgan, Ph.D.
This article was reviewed by Daphne Miller, MD, a family physician and an associate clinical professor at the University of California–San Francisco. See editor's note.
When the days grow shorter and darker, do you find yourself feeling blue? You’re not alone – and there are scientific reasons for that negative frame of mind. Studies show exposure to natural daylight can positively affect your mood, your alertness, and your overall health.
During the winter, some people feel depressed because they suffer from Seasonal Affective Disorder (SAD) brought on, in part, by less sunlight exposure. Sunlight is important to your health in another way: The natural light-dark rhythm of the day, dictated by the rising and setting of the sun, helps you sleep by maintaining natural circadian rhythms.
Find out more about sunlight – and how to get more of it (safely) this winter!
As the seasons change and the days grow shorter, some people find they sleep more, have less energy, crave more sweets and starchy foods, and feel depressed. These may be signs of seasonal affective disorder, or SAD. The exact causes of SAD aren't known, but are thought to stem from changes in our circadian rhythms due to the lack of sunlight. There also may be shifts in levels of the hormones melatonin and serotonin. Treatments for SAD include increased exposure to sunlight, light therapy, and medications. To learn more about SAD, visit the MedlinePlus SAD page.
Sunlight is made up of all the colors of the rainbow: red, orange, yellow, green, blue, indigo and violet. It encompasses the classic "ROY-G-BIV" color spectrum that you may have memorized in school.
Special cells in your eyes respond to light, especially light from the blue part of the spectrum. Blue light triggers parts of the brain that are important for alertness and cognition so adequate exposure is important for health. Incredibly, you don't have to “see” this light in order for your body to sense it. Researchers have discovered that blind people somehow sense this light and thus have normal circadian rhythms. That means that their internal biological clocks are working normally. A wide range of creatures, including monarchs, fruit flies, and mice, in addition to humans, seem to respond to blue light.
Although exposure to blue light is important for your health, most indoor lighting provides very low levels of the blue part of the light spectrum. In addition, we are exposed to much less blue light from natural sunlight during the shorter days of winter.
If you've ever had jet lag or done shift work, you've experienced the consequences of an altered circadian clock. Getting off schedule can affect your sleep and performance, and may play a role in the development of conditions such as depression, diabetes, dementia, heart disease, obesity, and some cancers.
The importance of maintaining a natural light-dark rhythm is dramatically illustrated by astronauts on the International Space Station, which is about 220 miles above the surface of the Earth. On Earth, astronauts experience a 24-hour light-dark cycle, just as the rest of us do. However, on the space station, they experience a 90-minute day because that’s how long it takes them to circle the Earth. That means they can see up to 16 sunsets per 24-hour-period! This shortened light-dark cycle greatly disrupts astronauts’ circadian rhythms, making it difficult for them to sleep properly.
1. Get outside. Encourage your family to get lots of natural-light exposure by spending time outside. Exposure in the morning may be better at helping to regulate sleep schedules.
2. Bring the outside inside. When you or your kids are indoors (at home, at work, or in school), you can benefit from sunlight via a window or skylight. Open blinds, add skylights, and consider trimming tree branches that block sunlight in your home, office, or school.
3. Light up. If you live in an area with very short days (towards the Antarctic), or really get blue during the winter months, you can talk with your doctor about trying a light box. The box provides an artificial source of light that is rich in the blue spectrum. This 'light therapy' may help with SAD, sleep disorders, jet lag, and other conditions.
4. Keep an eye out. Be aware that, just because a little blue light is good, it doesn't mean a lot is better. Too much blue light can damage the eye.
5. Power down at night. Exposure to lights from computer and TV screens and even alarm clocks in the evening may adversely affect sleep schedules. Power down this artificial light and opt instead to look at the light from the stars. (Or just go to bed!)
Please consult your physician if you think you suffer from Seasonal Affective Disorder or other disorders mentioned in this article. Sunlight is important for health, but extended exposure to direct sunlight should be avoided by wearing protective clothing and sunscreen. Learn more about sun safety.
Carol Torgan, Ph.D. is an award-winning health scientist, e-health strategist, educator and consultant. She is passionate about improving health by encouraging everyone to go outside and experience their five senses in four dimensions. Her Web site, www.caroltorgan.com, addresses the interplay of science, technology, and movement and includes a list of 100+ top play resources.
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