Not long ago, vitamin D was considered dull and definitely unsexy. Sure, it was known to help your body absorb calcium and prevent rickets (a childhood disease that softens the bones and causes debilitating deformities). But adding a dash of vitamin D to milk and a few other vitamin-fortified foods solved the problem, and no one thought much about vitamin D— until recently.
Today, vitamin D has leapt to the forefront of the supplement world, thanks to several new studies that suggest it plays a role in the prevention of cancer and other diseases. It’s no longer treated as a simple calcium-booster— vitamin D now has its own starring role as a hormone that triggers a range of cellular processes. Time will tell if science validates this promising new research, or if it becomes another dead end in the vast maze of nutrition science. In the meantime, there’s good reason to make sure your body has a solid dose of the stuff.
Vitamin D is naturally present in very few foods, but your skin has the ability to create this wonder drug when you expose it to the ultraviolet rays of the sun. The cells that carry out this operation lie at the bottom of your epidermis. You need surprisingly little exposure to the sun to maintain a healthy supply of vitamin D. The rule of thumb is 10 or 15 minutes of direct sun exposure, two or three times a week, on just part of your body (say, your face, hands, and arms). After that, it’s time to reach for the sunscreen.
Unfortunately, the vitamin D manufacturing process doesn’t work well in diffuse sunlight—say, in the winter months of a Northern state. Cloud cover and pollution also dramatically reduce the amount of ultraviolet light that reaches your skin. For example, in Boston, sunlight is too weak to trigger vitamin D synthesis from November through February. To make up the difference, you can take a vitamin D supplement—typically, 1,000 IU each day (look for this measure on the bottle), until summer rolls around again. This is roughly the amount of vitamin D that you’d get from 10 glasses of milk.
Supplementing your diet with vitamin D is particularly important if you have brown or black skin, because this natural sunscreen makes it more difficult to synthesize vitamin D.
The key point to remember is that the amount of sun exposure you need to synthesize vitamin D is very little in the summer months (or in a tropical climate). But in late fall and winter, you can run around in boxer shorts without producing a microgram of vitamin D.
Source of Information : Oreilly - Your Body Missing Manual