Friday, March 26, 2010

Vitamin D

Vitamin D is a fat-soluble vitamin that functions like a hormone. It is not a truly dietary essential, because if you spend time in the sun, you can make it in your skin. The current requirement is now under review because of this. Emerging science suggests that vitamin D may aid in the prevention of diabetes and heart diseases, schizophrenia and cancer. This vitamin is a family of many compounds with only two being the most active: ergocalciferol (D2) and cholecalciferol (D3). The skin can make a version of vitamin D from cholesterol and then send it to the liver and kidney for final activation.


Its primary role is as a regulator. It is like the conductor of an orchestra. It tells cells what to do. There are receptors for vitamin D on cell membranes and nucleus of cells that receive the instructions from it. It regulates blood calcium level with the help of other hormones. Some studies suggest that vitamin D may protect your immune system and even help in cancer prevention.

The recommended amount of vitamin D is 5 micrograms for those under 50. The synthesis of vitamin D decreases in individuals above 50, so their requirement is 10 micrograms per day. Sometimes you may see the amount of vitamin D in nutrition labels in International Unites (IU). Remember this equation: 1 microgram = 40 IU.

There are many factors that can influence the vitamin D synthesis in your skin. Where you live is an important factor. In Texas you’ll have more sun exposure than in London. Skin color: if you’re African American, you have melanin on your skin that acts as a natural sunscreen, and you don’t make as much vitamin D in your skin. If you wear sunscreen you can reduce the synthesis of vitamin D. Put your sunscreen right as you walk out the door, and you’re still going to have vitamin synthesis because sunscreen takes about 10 minutes to activate. 10 to 15 minutes a day at the peak sun level is a good amount of exposure. I’m not promoting sun burn or skin cancer, keep it to 15 minutes.

Food sources of vitamin D are few, and most are fortified foods. Skim milk is fortified with vitamins A and D. Breakfast cereals are usually fortified with vitamin D. Oily fish, salmon for example, are good sources. Egg yolk and butter also are good sources.

Vitamin D Deficiency

The classic vitamin D deficiency symptoms are rickets and osteomalacia. This is a softening of the bones, a little different than osteoporosis. Deficiency can increase the fracture rate in older people, and also may explain why some people don’t respond to traditional osteoporosis treatment. Estimates of vitamin D deficiency in the United States suggest that up to 50% of African American adolescents are vitamin D deficient. This is the major nutritional deficiency in the United States. The challenge is that with obesity vitamin D is held in body fat, and that means it is not available in the blood.

Some experts suggest that we have an epidemic of vitamin D deficiency because the recommended requirements are too low. If you are one of the two thirds of Americans who are overweight, your vitamin D requirement is going to be higher. Some of these dissenting experts suggest that the requirement for optimal blood levels may be as high as 2000 IU.

According to Dr. Michael Holick, having sun exposure enough to induce mild redness can be considered equal to a dose of 20000 IU. The sun can be a powerful ally. I’m not promoting skin cancer, but never going outside is not very nice.

With these high amounts, shouldn’t we be concerned about toxicity? Sun exposure is not toxic, as the skin can regulate the amount of vitamin D precursor that is sent to the liver. We’ve got the ability in our body to regulate how much we’re getting. The brakes are in the skin, the liver and the kidney. Supplements can be toxic though, and the upper limit is 2000 IU according to the Food and Nutrition Board.

The best advice I can give you is to check your blood level of vitamin D at your next doctor’s visit. This is the best guarantee that you, as an INDIVIDUAL, are getting an adequate amount. Your blood level should be greater than 30 nanograms per milliliter.

No comments:

Post a Comment

Template by bloggertheme