The New Wonder Vitamin

The vitamin of the decade has been chosen – Vitamin D. Everyone is taking vitamin D supplements for nearly every health benefit imaginable. It prevents osteoporosis, cancer, aging, flu, colds, heart disease, Parkinson’s Alzheimer’s, multiple sclerosis. You name it, vitamin D can prevent it. This is suspiciously reminiscent of vitamin C in the Linus Pauling era.

So, what do we know about vitamin D? In a nutshell: it is produced by human skin when exposed to sunlight with a UV index of more than 3. It is also found naturally in some foods, notably catfish, salmon, mackerel, sardines, tuna, eggs, beef liver, and for vegans, mushrooms.  Other foods such as milk and cereals are fortified with vitamin D. Severe deficiency causes rickets in children and osteomalacia (soft, easily broken bones) in adults. Severe excess results
in too much calcium in the blood with loss of appetite, nausea, vomiting, and kidney damage.

Too much vitamin D during pregnancy causes mental retardation and facial deformities in the fetus.  Vitamin D is used by nearly every cell in our bodies to regulate everything from calcium levels to immunity. Recent research has shown that too low or too high blood levels of vitamin D are associated with an increase in mortality from all causes. Low levels are strongly associated with
an increase in deaths from heart disease. As with most things, balance is the key: neither too high nor too low.

The evidence for vitamin D as a prevention for cancer deaths is impressive for colorectal cancer, less so for breast cancer and pancreatic cancer. It is clearly essential, along with calcium and other nutrients, in the prevention of osteoporosis. Studies of immunity are more theoretical than real; it does seem to provide some protection from colds and flu in the winter months when sun exposure is insufficient to maintain adequate blood levels. The evidence for
prevention of MS, Parkinson’s and Alzheimer’s is based on inadequate data. Research is in its earliest stages and the randomized controlled trials that will give more definitive answers have not been done yet. Taking large doses of vitamin D for long periods of time without this data, is like offering oneself up as a Guinea pig in an experiment without anyone overseeing the effects.
Do so at your own risk.  

That said how much vitamin D3 (not D2) should you take? The consensus seems to be that the RDA of 200-600IU per day is too low and should be closer to 1,000IU, especially in the winter months. There is no way to know how much you should be taking without a blood test to find out where you are now. If your level is low, ask your doctor how much to take and be sure your blood test is repeated in 3-6 months. If you are pregnant do not take vitamin D without your physician’s okay. And keep watching for the research that will someday tell us the truth about vitamin D.

Judith J. Petry, M.D., resident of
Westminster, Vermont