(Revised 9/20/10 with the addition of the information on heart failure.)

Last year’s update on vitamin D mentioned studies that documented various benefits of correcting the recently recognized pandemic of vitamin D insufficiency. There have been additional dozens of important studies since the 2009 update. However instead of writing about the individual studies, this column will give an overview of vitamin D and will try to answer the question, “How can one substance have so many beneficial effects on humans?”

First, vitamin D is not a vitamin. A vitamin is something that is supplied to humans from food. Vitamin D is not supplied by food in a significant amount, it is produced in the skin by sunlight. There is NO vitamin D naturally found in cow’s milk; the practice of adding 100 units to every 8 oz. of cow’s milk started almost a century ago was done to stop rickets in children. This dose does prevent rickets, but does little else. 400 units of Vitamin D a day only raises the level 5 nanograms (ng). Most Americans have levels that are 10 to 20 ng. below the “normal” level of 32 ng. and way below an ideal level, We’ve all seen people with high levels of vitamin D. Lifeguards in August have levels frequently have levels over 100 ng.

Vitamin D increases calcium absorption taken in from the diet. With insufficiency, only 10-20% of calcium is absorbed. With proper vitamin D levels, 60-80% of calcium is absorbed. Since calcium goes to the bones, this explains the prevention of rickets. However now it is known that virtually all osteoporosis is associated with a level of vitamin D below 32 ng. Prior to 10 years ago, almost every study done on osteoporosis used a dose of 400 units a day, and most showed no effect on osteoporosis or fractures. As late as a few years ago, newspapers trumpeted the wrong information that vitamin D didn’t prevent fractures. However all studies using larger doses of vitamin D have shown a large reduction in fractures. In fact, one critical study showed that large doses given to elderly hip fracture patients reduced further fractures and reduced falls within 6 months. (Muscles also contain vitamin D receptors and correction of insufficiencies increases muscle strength in the elderly).

Hyper-proliferation of cells is what occurs with cancer. Vitamin D has repeatedly been shown to prevent this. Many large studies have now shown that various types of cancers are associated with very low vitamin D levels. In a well publicized cancer study that spanned 8 years, the lowest levels of vitamin D were associated with the worst outcome and highest mortality in breast cancer. Many other studies have measured vitamin D in various types of cancer, and the results have always shown lower levels with the cancer. One study showed the incidence of breast cancer continued to decrease up to levels of 52 ng. Some vitamin D experts have predicted that the breast cancer rate would be reduced 50% if every woman’s vitamin D level was only 40 ng. Similar studies exist with prostate cancer and colon cancer. PSA levels in prostate cancer were shown to decrease with Vitamin D over 20 years ago. Thyroid cancer cells stop multiplying in a test tube when vitamin D is added. Lung cancer in smokers is less common the higher the vitamin D level, and in fact prognosis is better with higher vitamin D levels once lung cancer occurs. No one should misunderstand this data; it does not invalidate the many known causes of some various cancers. It is simply a factor that prevents the formation of a cancer in the presence of various known causes.

It was known in the 1970’s that MS and juvenile diabetes were less common the closer to the equator (more sunlight, more vitamin D). A study in Finland showed that giving a large number of infants high doses of vitamin D cut down the incidence of juvenile diabetes by a remarkable 80% a decade later. A recent study showed an 85% improvement in MS. These diseases, along with rheumatoid arthritis, lupus, and many other autoimmune diseases,involve cells within the body becoming modified by unknown factors and attacking the body, causing the illness. Vitamin D has been shown to keep our important immune system normal, and prevent any harmful changes to it.

Vitamin D has been shown to stimulate the production of antimicrobial peptides, a class of natural antibiotics. These have activity against bacteria and viruses. Think about it; why do flu epidemics occur during the winter and not the summer? Why do these epidemics occur in June and July in the southern hemispheres where the seasons are reversed? (Answer -lower vitamin D levels). In fact, the horrible pandemic of swine flu epidemic in the few years before 1920 tapered off in the summer before restarting. There are many published studies demonstrating this property of vitamin D.

Vitamin D levels have been shown to correlate with survival many years after bypass surgery.

In September, 2010, an 8 year study showed that deaths from heart failure were 3.4 times higher in patients with vitamin D levels less than 20 ng. and 2.0 times higher with levels 20 to 29 ng. vs.>30 ng.

Although much more research is being done, the existing research is convincing and totally unlike the anti-oxidant research (Vitamin C and B's)that has been called into question. Granted, it sounds too good to be true. Vitamin D is very inexpensive, so there are no advertising budgets to help spread the word. Vitamin D could have a profound effect on health care expenditures; it has been called a national health care plan in itself. It makes sense that Vitamin D is so basic to life and health. Scientists agree that life began near the equator. Early humans had unlimited access to sunlight, and didn’t have sunscreen or a wardrobe, so at one time humans’ vitamin D levels were very high.

The understanding of the importance of Vitamin D remains the most important preventive medicine development in over a century.