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22 January 2008

It's Winter - Do You Know Where Your Vitamin D Is?

John Cannell, MD, Director of the Vitamin D Council and author of the Vitamin D Newsletter has looked at recent conflicting media coverage of the effects of vitamin D on cancer. The December 2007 issue of the newsletter addresses how studies have been interpreted and how biased interpretation can adversely affect public health policy and your health.

You can also read the latest studies that link vitamin D deficiency to risks for cancer and make your own independent conclusions.

According to Dr. Cannell, Dr. Lichtenfeld, spokesman for the American Cancer Society has indicated that Americans continue to wait for more randomized, control trials before addressing their vitamin D deficiencies, even though a large volume of epidemiology studies indicate that vitamin D deficiency is a common finding in people of all age groups around the world.
At the same time, after risk/benefit analysis the Canadian Cancer Society has advised all Canadians to take 1000 IU of vitamin D daily. The Food and Nutrition Board, that sets U.S. nutrient recommendations currently recommends 2000 IU of vitamin D per day as a safe upper limit dosage for anyone over one year old.

So why aren't U.S. public health organizations like the American Cancer Society willing to increase the recommendations for adequate intake of vitamin D, like the Canadian Cancer Society have done?

Currently the Food and Nutrition Board recommends adequate intake of vitamin D at 200 IU for infants to 50 year olds, 400 IU for 51 to 70 year olds and 600 IU for those 71 and older. These recommendations persist, even with the current established safe upper limit dose of 2000 IU daily, even for one year olds. Is it good for your health to stick with these outdated government recommendations?

In the book Nutrition and Bone Health, Michael Holick, PhD, MD of Boston University and Bess Dawson Hughes, MD, Professor of Medicine at Tufts University discuss current vitamin D recommendations and the most accurate vitamin D blood test.

U.S. recommendations for adequate intake of vitamin D are based on research available prior to 1996, about 11 years ago! Also, current recommendations in the U.S. are based on the effects of vitamin D on bone health and calcium absorption but do not reflect, or even acknowledge the other vital biological functions of vitamin D, including its role in cancer prevention.

U.S. recommendations for vitamin D intake do not take into account the function of vitamin D in the regulation of blood pressure, insulin production, regulation of immune function and cell growth.

One very important step that you can take towards improving your own health is to ask your physician for a vitamin D test. The test is called a 25 hydroxy(OH)2 D blood test. It is inexpensive and the information provided is invaluable, especially during the winter months when your vitamin D levels may drop significantly with decreased exposure to sunlight, particularly if you live in northern regions of the country.

If your physician doesn't think that it is important to assess your vitamin D status, it may be wise to find a physician that understands the current scientific evidence regarding the importance of vitamin D to your health.

Or, you can directly order your own vitamin D blood test. Direct Labs is one source for screening tests as is the Life Extension Foundation. A requisition form is sent directly to you and you have your blood drawn at a lab where you live. In many cities you can have your blood sample taken at a convenient Lab Corp location or even at the lab that your doctor uses.

Vitamin D exists in several forms in the human body. Sometimes physicians order a test called the 1,25 (OH)2 D test. This is the most potent or active form of vitamin D in the human body, but according to Dr. Holick and Dr. Dawson Hughes, measuring 25(OH)2 D is a better blood test for assessing vitamin D status and say, frankly that the 1,25(OH)2 D blood test is "useless" in the assessment of vitamin D status.

Vitamin D3 derived from sunlight is called cholecalciferol. It is activated in the liver to 25(OH)2 D, also called calcidiol. From there, it enters blood circulation and travels to tissues, including the kidneys, where enzymes activate it to its most biologically active form, 1,25(OH)2 D, also called calcitriol.

As discussed in Dr. Holick and Dr. Dawson-Hughes' text, blood levels of this later form, 1,25(OH)2 D can be normal or even elevated at the same time that a person has vitamin D deficiency. Why? Because a vitamin D deficiency can cause a condition called hyperparathyroidism.

The human body, in an amazing attempt to normalize vitamin D concentrations at a cellular level, increases production of PTH (parathyroid hormone) that signals the kidneys to increase production of 1,25(OH)2 D.

If this sounds confusing, it can be! At least the first time you read it. Vitamin D is really a "prohormone" and is activated like other hormones in the body, through a process of hormonal signaling.

For the purpose of nutritional assessment of vitamin D status, make sure you request the 25(OH)2 D test, not the 1,25(OH)2 D test.

Dr. Holick,an eminent international vitamin D researcher recommends that lab reference ranges for vitamin D blood tests be raised. He has suggested an "optimal" healthy range of 25 (OH)2 D at 45-50 ng/ml. Most labs currently use a range of 20-56 ng/ml as "normal".

According to Holick, "Any levels below 20 ng/ml are considered deficiency states and will increase your risk of breast and prostate cancer and automimmune diseases like MS and rheumatoid arthritis".

And, by all means, read Dr. Cannell's December issue of the Vitamin D Council Newsletter. The Vitamin D Council website is an excellent source for up-to-date research regarding the benefits of maintaining healthy vitamin D levels.


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