Yes, we get it. Vitamin D has reached superstar status.
It strengthens our bones, battles cardiovascular disease, ameliorates chronic pain, plays a positive role in a variety of autoimmune diseases, lessens depression, and reduces the risk of cancer.
And it might be contributing to an early death.
Research findings out of Copenhagen published this past spring in the Journal of Clinical Endocrinology and Metabolism confirmed that too little vitamin D increases mortality, and uncovered that too much vitamin D can likewise kill us.
I noted similar disturbing conclusions made during research presentations at the American Society of Bone and Mineral Research annual meeting a couple of months ago in Minneapolis.
The Copenhagen study was a comprehensive undertaking, based on blood samples from more than a quarter of a million Copenhageners, who had visited a doctor for general health reasons, and who at the same time had their vitamin D levels checked.
But while some in the health care establishment can now perhaps caution, at least in a preliminary fashion, against unlimited intake of vitamin D, the world is still awaiting the explanation for this increased mortality phenomenon, and if they should believe it—particularly when considered against the backdrop of the Institute of Medicine vitamin D recommendations of 2011: The Institute of Medicine recommended tripling the daily intake for most children and adults to 600 IU per day, up from 200 IU/day. It goes without saying that this recommendation is not without controversy.
So, how much vitamin D does a human need every day? As with many dietary components, and especially for vitamin D, which the human body can make upon exposure to sunlight, serum levels vary widely, probably reflecting genetic background, diet, latitude, time spent out-of-doors, body size, developmental stage, and state of health, as well as plasma levels of vitamin D binding protein. The actions of vitamin D could also vary with the expression of various isoforms of the vitamin D receptor. Because rigorous and well-controlled dietary studies are often lacking in humans, recommended daily intakes for vitamins are sometimes as much matters of opinion as of fact, or are extrapolated from studies in model systems. In practice, most urban dwellers do not get much exposure to sunlight, and diet generally does not supply sufficient amounts of vitamin D: a serving of fish may contain 200-500 IU; a cup of a fortified dairy product (cow’s milk, yogurt) supplies 100 IU. Thus, for many of us, supplementation is required.
Health authorities in both the US and in Denmark are under great pressure from vitamin D proponents among physicians and the pharmaceutical industry to increase the recommended doses of the vitamin. And it should be noted that there is still a higher mortality associated with too little vitamin D than with too much. Among the Copenhagen subjects, there were more who lacked vitamin D than there were of those who have too much of it. (Some 2,500 of the test subjects had too much vitamin D, whereas more than 20,000 had too little.)
The Office of Dietary Supplements (ODS) at the National Institutes of Health (NIH) leads and sponsors several efforts to advance scientific understanding of the importance of vitamin D to health. These efforts have included:
• measurement of vitamin D levels in foods;
• assessment of vitamin D status of the U.S. population;
• development of a reference measurement procedure and standard reference materials to precisely measure this nutrient;
• systematic review of scientific literature used in updating the vitamin D recommended dietary allowances and safe levels of intake; and
• an international effort to standardize measurement of serum vitamin D levels in populations around the world.
ODS also sponsors conferences and workshops on vitamin D and leads a federal working group on this nutrient to identify and help meet research needs.
Further research will be performed, the dust will settle, and the future will find us with a little more knowledge about what to do with vitamin D.
In the meantime, it’s okay to sing the praises of vitamin D. Just expect a lot of dissonance before we get anywhere near consonance.