A prescription for better health: Go alfresco

Most of us spend the vast majority of our time inside. According to one government estimate, the average American spends 90% of his or her life indoors, and as we get older we become even more inclined not to venture out.  But is all this indoor time hurting our health?

The study results are ticking up: spending time outdoors seems to have discernible benefits for physical and mental health. Granted, some are merely by association and can be achieved by other means, perhaps while indoors, but often only with a good deal more trouble and expense. Here are five potential benefits of spending more time outdoors:

1. Your vitamin D levels will go up

Exposing your skin to sunshine — actually, ultraviolet B (UVB) rays — enables the body to make vitamin D, which is why it's also known as the "sunshine vitamin." Research suggests vitamin D may have protective effects against everything from osteoporosis to cancer to depression to heart attacks and stroke.

Of course, it has to be sunny out, and there are some snags. Where you live, the season, and the time of day affect how much UVB reaches your skin. The farther you live from the equator, the less UVB radiation you receive. Vitamin D production is affected by age (people ages 65 and over generate about a fourth as much as people in their 20s) and skin color (African Americans have, on average, about half the levels of vitamin D in their blood as white Americans).

Another problem: sunscreens are most effective at blocking UVB light, the part of the spectrum that causes sunburn, but UVB also happens to be the kind of light that kick-starts the generation of vitamin D in the skin.

The either-or of sunscreen and sunshine vitamin has stirred up a lot of controversy and debate between pro-sunscreen dermatologists and the vitamin D camp. But there is plenty of middle ground here: some limited sun exposure on short walks and the like, supplemented with vitamin D pills if necessary, and liberal use of sunscreen when you are out for extended periods, particularly during the middle of the day.

2. You'll get more exercise (especially if you're a child)

Being outside isn't a guarantee of being active. Still, there's no question that being outdoors is associated with activity and indoor living is associated with being sedentary, particularly for children. According to some surveys, American children spend an average of 6½ hours a day with electronic media (video games, television, and so on), time that is spent mainly indoors and sitting down. British researchers found that children are more than doubly active when they are outside.

Adults can go to the gym. Many prefer the controlled environment there. But if you make getting outside a goal, that should mean less time in front of the television and computer and more time walking, biking, gardening, cleaning up the yard, and doing other things that put the body in motion.

3. You'll be happier (especially if your exercise is 'green')

Light tends to elevate people's mood, and unless you live in a glass house or are using a light box to treat seasonal affective disorder, there's usually more light available outside than in. Physical activity has been shown to relax and cheer people up, so if being outside replaces inactive pursuits with active ones, it might also mean more smiles and laughter.

Researchers at the University of Essex in England are advancing the notion that exercising in the presence of nature has added benefit, particularly for mental health. Their investigations into "green exercise," as they are calling it, dovetail with research showing benefits from living in proximity to green, open spaces.

4. Your concentration will improve

A study published in 2008 found that children with ADHD scored higher on a test of concentration after a walk through a park than after a walk through a residential neighborhood or downtown area. Other ADHD studies have also suggested that outdoor exercise could have positive effects on the condition. Truth be told, this research has been done in children, so it's a stretch to say it applies to adults, even those who have an ADHD diagnosis. But if you have trouble concentrating — as many do — you might see if some outdoor activity, the greener the better, helps.

5. You may heal faster

University of Pittsburgh researchers reported in 2005 that spinal surgery patients experienced less pain and stress and took fewer pain medications during their recoveries if they were exposed to natural light. An older study showed that the view out the window (trees vs. a brick wall) had an effect on patient recovery. Of course, windows and views are different than actually being outside, but we're betting that adding a little fresh air to the equation couldn't hurt and might help.