New data show vitamin D plays significant role in health

<p>Which single vitamin supplement has recently been shown to improve muscle strength, heart strength, insulin activity, thyroid function and the effectiveness of the immune system? Which same vitamin's deficiency is linked to osteoporosis, colon cancer, prostate cancer, pancreatic cancer, breast cancer, diabetes, depression, tuberculosis, rheumatoid arthritis, multiple sclerosis, bone pain and schizophrenia? This is the natural vitamin that is harder to get during the fall and winter months when the days get short and the temperatures turn cold.</p><p>The "wonder pill" is vitamin D-3 (cholecalciferol, usually labeled simply as "vitamin D"), which is not really a vitamin but rather a potent steroid hormone essential for human health. First discovered in 1926, vitamin D- 3 was thought only to help strengthen bones and prevent rickets, but recent research has revealed a much larger and surprising role for this hormone.</p><p>First consider the production of natural vitamin D-3 in our body, a unique and elegant multiorgan process, starting with the sunlight warming our skin. From sun-kissed skin, pre-vitamin D- 3 goes through the bloodstream to the liver, where it is processed into a new chemical. This new form of pre-D-3 then travels to the kidneys to be converted into the active form of vitamin D-3, ready to be used as a potent regulator of cellular growth in almost every tissue in the human body. It controls the development of both healthy cells and cancer cells. The potential significance of these findings is enormous.</p><p>But what happens when we protect ourselves from skin cancer by staying out of the sun, covering up and wearing sunscreen? We get an epidemic of vitamin D-3 deficiency that affects a large percentage of the population. More than 36 percent of otherwise healthy adults in the United States have been reported to be vitamin D-3 deficient.</p><p>At higher risk are the elderly, the homebound and those with liver or kidney disease. Even exclusively breast-fed infants may be deficient if their mothers' intake is inadequate. Dark- skinned people need more sun exposure than lighter-skinned people, and the only effective sunlight in our area is the summer sun high in the sky during the middle of the day when the UVB rays are able to penetrate the ozone layer.</p><p>These are exactly the rays we avoid to protect our skin from cancer. To solve this problem of opposing needs we must find other sources of the vitamin.</p><p>Scientists are beginning to suggest a daily intake of 1,000-2,000 international units (IU), instead of the previous recommendation of 200-400 IU per day. And contrary to what we used to believe, 1,000 IU daily is a safe amount to take. According to the Mayo Clinic Proceedings published in March 2006, overdosing on vitamin D-3 supplements would require a daily dose of more than 10,000 IU for at least two months.</p><p>The new requirements are difficult to meet through dietary sources. A tablespoon of cod liver oil provides more than 1, 200 IU, if you can stomach that daily dose. But you'd have to eat almost 10 ounces of salmon or 20 egg yolks, or drink 10 glasses of fortified milk each day to get the new minimal recommended requirements.</p><p>It may make more sense to take a supplement. Pharmacies and many supermarkets, natural foods stores and even warehouse stores stock the vitamin. It is not expensive - I recently found 1,000 IU tablets on sale at a Santa Rosa drugstore and got a six-month supply for $7.</p><p>This information is very new, and much remains to be discovered. For my part, when I go outside I plan to wait 15 or 20 minutes before I use sunscreen, and I'm taking vitamin D-3 along with my multivitamin and calcium.</p><p>I figure it's just a good dose of safe, supplemental sunshine.</p><p>Longtime Sonoma County family physician Dr. Stacey Kerr, a graduate of UC Davis Medical School, is certified in her specialty by the American Board of Family Medicine. Her columns are not intended as a substitute for hands-on medical advice or treatment. Consult your health care provider before adhering to any recommendations in this column. E-mail comments to drkerr@the-doctors-inn.com.</p>