By Dr. Michael F Holick

Dr. Holick is clearly the leading vitamin D researcher in the world. This month he writes an editorial in the American Journal of Clinical Nutrition in response to a study published in the July journal which documents that nearly half of African American women were deficient in vitamin D.

Dr. Holick, explains that the prevalence is actually far worse as the study was done in the summer, when vitamin D levels are typically higher, and, more importantly, outdated reference ranges were used to classify vitamin D deficiency.

Based on newer analysis of parathyroid hormone response to vitamin D challenges it appears that the normal range of vitamin D levels significantly underestimates vitamin D deficiency.

Dr. Holick asks the question why should we care if young healthy adult females are deficient in vitamin D, given that their skeletons have matured and there is no evidence of significant osteoporosis in this age group? Are there other, more insidious consequences of vitamin D deficiency for this age group?

Vitamin D is essential to maximize skeletal health from birth until death. Vitamin D as 1,25(OH)2D accomplishes this by increasing the efficiency of intestinal calcium and phosphorus transport.

Vitamin D deficiency causes a mineralization defect that results in growth retardation and rickets in growing children. The effect is more subtle in adults. Vitamin D deficiency causes osteomalacia, which is associated with nonspecific isolated or generalized bone pain, muscle aches, and muscle weakness, ie, symptoms similar to fibromyalgia.

It was recently suggested that a majority of Danish women with symptoms of fibromyalgia had severe vitamin D deficiency and osteomalacia. Vitamin D deficiency also causes secondary hyperparathyroidism, which can precipitate and worsen osteoporosis by increasing mobilization of mineral and matrix from the skeleton.

Vitamin D receptors exist in the intestine and bone for regulating calcium and bone metabolism and are also present in a wide variety of other tissues and organs, including the brain, pancreas, skin, gonads, stomach, colon, breast, mononuclear cells, and activated T and B lymphocytes.

Activated vitamin D (1,25(OH)2D) is one of the most potent inhibitors of cellular proliferation and inducers of cellular maturation and has important immunomodulatory activities on B and T lymphocytes.

People have a increased risk of dying from breast, colon, ovarian, and prostate cancer when they live further from the equator because they have less sunlight shinning on their skin to manufacture vitamin D. It appears that the cellular production of activated vitamin D3 may be essential for the regulation of cellular health, thereby decreasing the risk of developing some cancers.

African Americans, who are chronically vitamin D deficient, have a higher incidence and more aggressive forms of many cancers, including breast and prostate cancer. Men who are exposed to more sunlight can delay the onset of prostate cancer by more than 5 years. Children receiving vitamin D supplementation from age 1 year old on had an 80% decreased risk of developing type 1 diabetes.

How is it possible in this new millennium that vitamin D deficiency, a disease that plagued our ancestors from the 17th through 19th centuries, should still be a problem?

Why is vitamin D deficiency so prevalent?

There are very few foods that naturally contain vitamin D. It would be necessary to eat fatty fish such as salmon and mackerel 3-4 times per week to satisfy the body's vitamin D requirement. How much is an adequate intake? The 1997 recommendations by the Institute of Medicine is probably too low. The committee's charge was to make these recommendations on the basis of the literature.

Unfortunately, few studies have looked at the consequences of vitamin D deficiency in most age groups, including premenopausal women. It is likely that in the absence of exposure to sunlight, the adequate intake for vitamin D should be far greater than 800-1000 IU vitamin D per day. Can you get too much vitamin D from exposure to sunlight or the diet?

There has never been a reported case of vitamin D intoxication from excessive exposure to sunlight. However, it is clearly possible to overdose on oral vitamin D, especially if it the synthetic vitamin D2 ergocalciferol.

Therefore, increasing our vitamin D intake or casual exposure to sunlight may decrease the risk of some of the most common cancers, type 1 diabetes, and possibly multiple sclerosis. The only way to know a person's vitamin D status is to measure 25 hydroxy vitamin D levels. Thus, it is reasonable for everyone to have his or her 25(OH)D concentration measured once a year.

American Journal of Clinical Nutrition July 2002 76:3-4

Dr. Mercola's Comments:

Sad but true, it takes quite some time for the medical community to catch up to the scientists. I have been measuring vitamin D levels (25 hydroxy vitamin D) in most of my patients for the last six months. I have probably done more than 500 samples, and I can confidently tell you that in my section of the country, in the winter months, virtually everyone is deficient -- - when using the newer updated reference ranges. Using the older ranges, however, I would only classify about 5% as deficient. This reminds me of when I first opened my medical practice in 1985 and would inform patients they had elevated cholesterol levels. This was before cholesterol became popular and most doctors believed a person had no problem unless the cholesterol level was over 350. As the new kid on the block, I had a way to go to develop the necessary rapport for patients to believe what I was telling them. Many would venture back to their old doctor who would tell them their cholesterol level was just fine, don't sweat it. One of the reasons cholesterol finally became a national issue is that a drug solution was developed for it. And then things swung too far in the other direction. The new guidelines, in fact, suggest that half of the country should be on these drugs! Well, testing for vitamin D will not skyrocket like cholesterol testing because there is no expensive drug to push, thus making the public more aware. You'll have to fend for yourself on this one, folks. You can't rely on the media to expose the issue. If and when they do, it will be too late for most of you and you will have suffered decreased bone density and an increased risk of many cancers. But you don't have to wait for the media. You can read my vitamin D testing article and get up to date on this important topic before it is too late. Unless you are getting significant sun exposure on large amounts of your skin, in fact, I would advise reading the article right now. Related Articles: Test Values and Treatment for Vitamin D Deficiency Breakthrough Updates You Need to Know on Vitamin D