Vitamin D and Bone Health—Discussion Points Following the Recent Institute of Medicine Recommendations
AbstractThe 2011 Institute of Medicine recommendations for vitamin D—both the recommended daily amount (RDA) and the vitamin D status judged adequate for bone health—are too low. Calcium absorption, osteoporotic fracture risk reduction, and healing of histological osteomalacia all require values above 30 ng/ml, and probably even 40 ng/ml. Furthermore, the proposed RDA (600 international units per day up to the age of 70) is not compatible with the blood level of 25-hydroxyvitamin D (i.e., 20 ng/ml) recommended in the same report. Concerns regarding adverse consequences of higher intakes or status levels can be dismissed, in view of our extensive experience with outdoor summer workers(who regularly have values of 60 ng/ml or more) and the virtual certainty that human physiology evolved in—and is attuned to—an environment providing 10,000 IU/day or more.
At the outset, it is important to understand that the 2011 Institute of Medicine (IOM) recommendations for vitamin D1,2 can be taken at three levels of applicability. The first is the level of my own decision, for my own intake, informed not just by whim, but by my reading of the appropriate science. The second level is what I, as a physician, might recommend to patients who come to me for advice. And the third level is what policy-makers decide with respect to the population in general, many, perhaps most, of whom would be ignorant of the topic entirely and not able to make an informed decision for themselves.
Clearly, the needed level of certainty (the strength of the evidence— for whatever recommendations may be made) rises as one moves up from the first to the third level. In theory, I might disagree with the OM recommendations with regard to my own intake, or even with regard to what I recommend to my patients, and at the same time accept the recommendations for the public at large.
It is important to note that the IOM’s recommendations actually apply only to the general public and are explicitly predicated on a healthy population. They are not intended for patients with various medical disorders, either current or potential. Thus, they apply only in a very limited way to the advice that physicians give to their patients and, while it is useful for a physician to be aware of them, they do not constitute guidelines for his or her practice. A good example of that distinction is found in the vitamin D guidelines for physicians issued by The Endocrine Society3 just a few months after the IOM recommendations were formally released and by yet another set of guidelines, soon to be released, developed by the American Geriatrics Society (AGS). There is a sharp contrast between, for example, the IOM’s recommended intake for the general public up to the age of 70, set at 15 μg (600 international units [IU]) per day, and the Endocrine Society’s recommendation, set at up to 50 μg (2,000 IU) per day. Similarly, the Endocrine Society’s safe upper level (UL) for adults is 250 μg (10,000 IU) per day, while the IOM’s UL is 100 μg (4,000 IU) per day. Even larger differences will be evident when the AGS guidelines are published.
A further point of note is that the current IOM recommendations are explicitly intended to deal with skeletal endpoints only. The panelrequired evidence from multiple randomized trials to conclude that a particular health outcome was due to vitamin D status and, while they acknowledged that there may be some extra-skeletal benefits, they did not find evidence they considered sufficient to allow them to specifyintakes that might produce such benefits. Thus there is nothing in the IOM recommendations that would be specifically applicable for practitioners in the fields of psychiatry, obstetrics, oncology, infectious isease, and other disciplines.
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