On November 30, 2010 the Institute of Medicine (IOM) issued a new report from an expert panel on how much vitamin D people of various ages need. On the one hand the report was a step in the right direction as it increased the recommended level of Vitamin D for some people by as much as 3-fold and also doubled the “toxic upper limit (UL) from 2000IU to 4000IU. On the other hand a strong case can be made that the IOM’s panel did not raise recommended levels sufficiently for optimal health and it also seemed overly concerned about possible toxicity. An article in the Wall Street Journal about the IOM’s report led with the headline “Can Too Much Vitamin D Be Hazardous to Your Health?” and a CBS news story summarized the IOM’s report by saying “Vitamin D Report Shocker: High Doses Unnecessary, Risky”. The IOM report did state that even with the new higher recommended vitamin D levels that most Americans were already getting those high levels and it suggested that levels in excess of 4000IUs may be dangerous. In fact a major review showed no adverse effect from vitamin D intakes up to 10,000 IUs per day. 1 However, the IOM report and the media seemed to put more weight on a modest (17%) increased risk in kidney stones in the Women’s Health Initiative Study in women taking only 400IUs of vitamin D. Of course, a far more likely explanation in this study was the increased calcium intake, which is known to increase kidney stone risk. Much of the media hype about the supposed dan- gers of vitamin D supplements certainly were an exaggeration the IOM report could be criticized as excessively cautious. Certainly the main thrust of the report was that most Americans are get- ting plenty of vitamin D and was overly cautious about amounts in excess of the new recommended levels. The fallout from this report may be that Americans will be led to believe they need not be concerned about getting enough vitamin D as nearly everyone is already getting enough and taking supplements in excess of the 600IUs recommended is likely dangerous. If that is what most people get from the report and media hype the report and new guidelines while a step in the right direction may still end up doing more harm than good.
Where did the IOM’s expert panel go wrong?
The expert panel was led by a researcher whose main research focus has been with vitamin A. Excess vitamin A is quite toxic and can weaken bones and increase fracture risk even at doses not that much higher than the RDI. Indeed, excess vitamin A or its precursor beta-carotene have been shown to cause cancer in animals and humans. In addition the panel dismissed all the research indicating that lower levels of vitamin D ap- pear to increase the risk of a wide variety of diseases from colorectal, breast, prostate, and even aggressive skin cancers to developing a host of auto-immune diseases such as multiple sclerosis and type 1 diabetes. In addition they dismissed new data suggesting low levels of vitamin D may increase insulin resistance and related metabolic abnormalities that can lead the development of type 2 diabetes, higher blood pressure and cardiovascular disease. Low vitamin D levels can weaken bones and might contribute to depression. And more recently the evidence is growing that low levels of vitamin D seen in most Americans may also impair immune function and increase the risk of Influenza A infection, macular degeneration, and possibly even cataracts. Much of this research suggests that the need for vitamin D may be considerably higher to reduce the risk of these ills than needed to optimize bone health. However, because this research is still not conclusive and the optimal amount of vitamin D needed to minimize these other illnesses is not clear the IOM’s panel simply dismissed all this research and set their new vitamin D recommendations based only on what research shows is necessary for good bone health. There is some data showing an increased risk of several of types of cancer with high tissue levels of 25(OH)D (a metabolite of vitamin D) but these epidemiological studies involved people taking lot’s of cod liver oil as a source of Vitamin D. Cod liver oil is also high in vitamin A. Excess Vitamin A seems a more likely promoter of cancer than higher intakes of vitamin D.
Bottom Line: From this reviewer’s perspective, the IOM report was a small step in the right direction because it upped the vitamin D recommended intake and also doubled the UL but overall it was excessively concerned with unlikely risks from vitamin D supplements and overly dismissive of other likely benefits of getting more vitamin D from supplements or the sun that would be well in excess of their new recommended levels.
By James J. Kenney, PhD, RD, FACN
References: 1. Hathcock JN, et al. Am J Clin Nutr 2007;85:6-18
For more information on Vitamin D, see the Member Library and then Articles > Nutrition > Supplements - and there are many articles that review research for Vitamin D.
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.