RDA for Vitamin D Miscalculated by Institute of Medicine

In 2011 the Institute of Medicine increased the recommended dietary allowances (RDA) of vitamin D from 400 to 600 IU for people aged 1 to 70. This was a welcomed increase, but many experts argued that it was not enough and recommended doses over 1,000 IU daily. In a recent paper published in the journal Nature, researchers state that the IOM’s 2011 vitamin D RDA—which doctors across the country are basing their vitamin D recommendations on—was miscalculated.

They attempted to calculate the dose that would need to be given to achieve a vitamin D blood level of at least 20 ng/mL in 97.5 percent of the population, the blood level determined to be adequate by the Food and Nutrition Board (FNB).* The problem is that the FNB used group averages instead of individual averages to calculate the RDA. Using individual averages, a dose of 600 IU would only achieve a blood level of 11 ng/mL for 97.5 percent of the population, a level considered to be a deficiency.

Using the correct statistical calculations, the researchers estimated that a dose of 8,895 IU/day—almost 15 times the current recommendations—would be needed to achieve blood levels of 20 ng/mL or more.

“The public health and clinical implications of an error in the calculation of the recommended dietary allowance for vitamin D are serious,” noted Paul Veugelers, PhD, an author of the paper. “Current public health targets are not being met.”

In another paper by the same researchers in conjunction with other prominent vitamin D researchers, a re-evaluation of the vitamin D RDA to account for body weight was also called for. As it turns out, overweight and obese individuals require much higher vitamin D doses (in the range of 12,000 to 20,000 IU daily) to achieve the same blood level as their lean counterparts. “We recommend clinical guidelines for vitamin D supplementation be specific for normal weight, overweight, and obese individuals,” they noted.

Vitamin D supplementation is something I recommend for almost everyone. Dr. Smith and I have blogged many times on the benefits of optimizing your vitamin D level. The Vitamin D Council is an excellent resource for more information on this essential nutrient.

*(Many experts feel that this “adequate” level is anything but, and recommend at least 50 ng/mL as an optimal level.)
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