New IOM Report on Vitamin D Intakes: What Clinicians Need to Know

JoAnn E. Manson, MD, DrPH


December 09, 2010

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Hello, this is Dr. JoAnn Manson, Professor of Medicine at Harvard Medical School, Brigham and Women's Hospital. I would like to talk with you today about the new report on vitamin D intake from the Institute of Medicine (IOM) that was released on November 30 of this year. I was a member of the IOM committee that produced this report. It's important to understand that the IOM committee conducted a comprehensive and rigorous review of the evidence for vitamin D in both skeletal and nonskeletal health outcomes. So we considered not only bone health but also the role of vitamin D in preventing cancer, cardiovascular disease, diabetes, and autoimmune disorders.

The IOM committee concluded that the evidence that vitamin D has benefits for bone health is compelling, but for nonbone health outcomes, including cancer and cardiovascular disease, the evidence was found to be inconsistent, inconclusive as to a cause-and-effect relationship, and not yet sufficient to inform nutritional requirements for vitamin D. The IOM committee determined that an intake of vitamin D of 600 IU per day for ages 1-70, and 800 IU per day for ages 71 and older, would cover the requirements (the needs of at least 97.5% of the North American population.) This would correspond to a blood level of vitamin D of 25 hydroxy-D of 20 ng/mL which should also cover the requirements of at least 97.5% of the population. It's important to understand that the IOM committee made an assumption of minimal or no sun exposure in setting the recommended dietary allowances (RDAs) for vitamin D. This was to provide a margin of safety because of the variability in skin synthesis of vitamin D according to season, latitude, skin pigmentation, genetic factors, and other variables, and also because of concerns about skin cancer with increasing exposure to solar radiation.

The IOM committee concluded that more is not necessarily better when it comes to vitamin D intake, that there may be risks from both low levels (like deficiency of vitamin D) as well as very high levels of vitamin D, and that there may, in fact, be a U-shaped curve, which has been seen with many other nutrients as well. In fact, the IOM committee considered that some of the previous lessons with other nutrients, such as beta carotene and vitamin E, should be seen as cautionary tales in that these nutrients were shown to have benefits in observational studies, but randomized clinical trials did not confirm these benefits and even suggested some risk at very high levels of supplementation.

Overall, the committee cautions that blood labs for vitamin D have variability in terms of cut-points used for vitamin D deficiency, and insufficiency, and that the cut-points used are often not evidence based, and that these cut-points may be leading to an overestimate of the prevalence of vitamin D inadequacy in the population. Overall, the committee recommends that much more research be done on the role of vitamin D in preventing the nonskeletal outcomes (cancer, cardiovascular disease, diabetes) and many other health outcomes, and that professional societies and federal agencies work together to develop evidence-based cut-points for vitamin D inadequacy and insufficiency to avoid problems with both undertreatment and overtreatment.

Thank you very much.


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