eileen

The Vitamin D Deal
BY RACHEL HERSCHENFELD, M.D. - DERMATOLOGIST

A vitamin is a small organic molecule essential for normal metabolism and growth. Since it cannot be synthesized by the body in adequate amounts, it must be obtained in the diet. According to this definition, vitamin D isn't even a vitamin, since very large amounts can be synthesized in the skin. However, many if not most people don't make enough vitamin D and need to consume it in food or supplements.
Vitamin D has been in the news a lot partly because of this very problem. It turns out that the skin can synthesize vitamin D only if it is exposed to adequate amounts of sunlight. So, people who don't get a lot of sun, such as patients in hospitals, or elderly people living in institutions, are often deficient in vitamin D. Even healthy active adults, who live in northern latitudes, such as in New England, are frequently deficient in vitamin D, as are people who live in sunny climates but habitually cover their skin. The UV rays that produce vitamin D in the skin are the very same UV rays that produce sunburn and that are blocked by sunscreen, shade, clothing and dark skin pigmentation, so even people who are active outdoors can be deficient in vitamin D.
Why do we care? Vitamin D is essential for regulating blood calcium levels and for promoting calcium absorption to maintain strong bones. It also regulates certain immune functions and can decrease the proliferation of normal and cancerous cells. This may explain why low vitamin D levels are associated with increased risks of certain kinds of cancer and other diseases, and why vitamin D supplementation has been shown to decrease the risk of some cancers in post-menopausal women.
Fortunately, it is easy to supplement vitamin D levels. The recommended daily intake of vitamin D3 is 400 IU daily, although many experts recommend intake of 800 IU daily for children and adults. There are several good dietary sources: a 3.5 ounce serving of fresh wild salmon has between 600 and 1000 IU of vitamin D3 (farm-raised salmon may only contain 100 to 250 IU in the same size serving); canned tuna contains about 230 IU in a 3.6 ounce serving (which is a little more than half a can). Fortified milk, yogurt, cheese, orange juice and breakfast cereals often contain 100 IU of vitamin D3 per serving. Over-the-counter supplements containing vitamin D3 are also widely available.
Finally, there is the option of careful, sensible sun exposure. It is difficult to calculate "adequate" sun exposure because the amount of sun needed for a person to synthesize enough vitamin D varies with season, latitude, time of day and skin pigmentation. These factors affect the amount of UV that reaches and is absorbed by the skin. Also, older skin has less capacity to synthesize vitamin D. For most people, 5 to 10 minutes of sun exposure on the arms and legs twice a week may be enough to maintain vitamin D levels. With sun exposure, moderation is key; too much UV exposure and sunburns increase the risk of skin cancer. So, it is still important to avoid excessive sun exposure and to use sunscreen daily to minimize this risk.

SOURCE LINK: http://www.washingtonpost.com/wp-srv...nse/mar08.html

__________________
"under exposure to UV rays is as dangerous as overexposure....this is D life" eileen