What do I need to know about vitamin D?
Over the last few decades a number of vitamin supplements have had their 15 minutes of fame as they were promoted for unproven health benefits. Linus Pauling incorrectly postulated that vitamin C supplements could prevent and treat viral infections, a concept which still persists and is manifested in the extreme by a story I recently heard of a man who decided to forego his usual daily bottle of cola in favor of orange soda because he had a cold! Vitamin E supplements were widely promoted for heart health because vitamin E is an anti-oxidant. But studies failed to show any benefit and there may be adverse effects from taking vitamin E supplements regularly.
Now vitamin D is ascendant. We have known for a long time of the vital role that vitamin D plays in helping the body to absorb calcium and maintain or improve bone strength, though the jury is still out on whether taking vitamin D and calcium as supplements (as opposed to normal dietary intake) has any benefit in preventing fractures. Indeed, the United States Preventive Services Task Force advises against recommending calcium and D supplements for the purpose of preventing fractures in people who are ambulatory because of the lack of evidence of benefit. In recent years the role of vitamin D has been studies in relation to the immune system, in muscle function, in preventing a variety of cancers and heart disease, and even in the prevention and treatment of diabetes. Though benefits of vitamin D supplements in these areas has been theorized, it has not been proven in any of them. Nonetheless, the flurry of interest in vitamin D has led to the practice of routinely checking blood levels in people with heart disease and with diabetes, and sometimes even in healthy people. This is despite the fact that there is no agreement on what constitutes a below normal blood level of vitamin D.
Maine’s own Dr. Clifford Rosen (late of St. Joseph’s hospital and now at Maine Medical Center) is one of the world’s experts on vitamin D and calcium metabolism. In an article that he published last summer he and his co-author stated that there is no clear link between vitamin D and the progression of diseases like cancer, muscle problems, the immune system, etc., and they warn against high doses of D, because high levels may actually be associated with an increased risk of cancer, mortality form heart disease and, ironically, falls and fractures.
So what is one to do about vitamin D? My best advice is to be sure to maintain adequate daily intake (600 to 800 IU a day) through eating foods containing vitamin D, which include cod liver oil, egg yolks, tuna, swordfish, beef, liver, swiss cheese, and if you have expensive taste, caviar! Many dairy and soy products are also fortified with vitamin D. There is good reason to believe that vitamin D intake through eating healthy foods is better than taking supplements. Moderate sunshine exposure helps your skin to make vitamin D, but it is the ultraviolet rays that accomplish this and UV light also increases the risk of skin cancer. If you have been on vitamin D supplements or wonder if you should take them, have an informed discussion with your primary care provider. And in most circumstances you do not need to have a vitamin D blood level checked.