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Top Vitamin D Review Just Published

This is probably one of the best summaries on vitamin D published to date as it chock full of exciting tidbits on vitamin D. Dr. Michael Hollick is the author and he is one of the top experts on vitamin D in the world. The AJCN is one of the leading nutritonal journals in the world. Dr. Hollick reviews the role of vitamin D deficiency in increasing the risk of many common and serious diseases, including:

  • common cancers
  • type 1 diabetes
  • cardiovascular diseas
  • osteoporosis

During exposure to sunlight, a form of cholesterol is actually activated through the sunlight to form vitamin D3. Interestingly, lifeguards and sun worshippers have never been reported to suffer from vitamin D intoxication due to excessive exposure to the sun. It would appear that there is a feedback mechanism that limits too much vitamin D from being produced due to excessive sun exposure. However, this is not true from taking oral vitamin D supplements, which is why testing of vitamin D levels is highly advised if you are taking oral vitamin D supplements.

Interestingly, people with very darkly pigmented skin require 10 to 50 times the exposure to sunlight to produce the same amount of vitamin D3 in their skin as does a white person. This is important as very few foods naturally contain vitamin D. Good sources are:

So why do we need vitamin D? For a variety of reasons. Without vitamin D, the small intestine absorbs no more than 10 percent to 15 percent of dietary calcium. This can lead to secondary hyperparathyroidism that can cause osteoporosis. However there are major addtionial consequences of vitamin D deficiency such as:

  • colon, prostate and breast cancers
  • multiple sclerosis
  • high blood pressure
  • psoriasis
  • type 1 diabetes
  • rheumatoid arthritis

One of the most intriguing, important and unappreciated biologic functions of vitamin D is its ability to down-regulate hyperproliferative cell growth. Normal and cancer cells that have a vitamin D receptor often respond to vitamin D by decreasing their proliferation and enhancing their maturation.

Although breast feeding has become very popular it has actually increased vitamin D deficiency as there is very little vitamin D in breast milk. Kids were designed to get it from the sun, not from the breast and that really is the ideal source to get it from and the one that we should all really strive for. However, for those of us unable to get sun exposure the cod liver oil certainly makes a lot of good sense.

American Journal of Clinical Nutrition March 2004

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