Published on June 7, 2017
What is an RDA? Who sets the standards?
The National Academy of Sciences (NAS) is a private, non-profit institution comprised of scholars in various scientific fields, most of whom donate their time. It was created by an act of Congress and signed by President Abraham Lincoln in 1863. Its purpose is to provide independent, fact-based recommendations on scientific matters including science, engineering, and medicine. When you hear about the Institute of Medicine (IOM), this is the branch under NAS that is concerned with medical matters. In 2015 the name was changed from the Institute of Medicine to the National Academy of Medicine, but with regard to recommendations that were set before the change people still refer to the IOM.
Similarly, the recommended dietary allowance (RDA) is what we are used to hearing, but the broader, more correct term is dietary reference intake (DRI). DRI has three elements – the RDA, an adequate intake level (AI), created when there is not enough evidence to provide an RDA, and a tolerable upper limit (UL).
For vitamin D they have defined an RDA and UL.
|0-6 months||400 IU||1,000 IU|
|0-12 months||400 IU||1,500 IU|
|1-3 years||600 IU||2,500 IU|
|4-8 years||600 IU||3,000 IU|
|9-13 years||600 IU||4,000 IU|
|14-18 years||600 IU||4,000 IU|
|19-50 years||600 IU||4,000 IU|
|51-70 years||600 IU||4,000 IU|
|>70 years||800 IU||4,000 IU|
The RDA is set at a level determined to be sufficient for 97.5% of the population meet or exceed the specific nutrient requirement. So, for the case of vitamin D, the panel concluded that 20 ng/ml (50 nmol/L) was the correct goal for vitamin D blood levels (25(OH)D) to maintain bone health and the RDA was set to allow 97.5% of the population to get to that level.
What does the vitamin D community think?
The researchers who disagreed with the new recommendations had two points of contention: 1) That 20 ng/ml is not enough for bone health, the goal should be 30 ng/ml (75 nmol/L) and 2) That even if the goal is 20 ng/ml, the DRIs set will not meet that goal for 97.5% of the population – the math was not done correctly (explained in this blog).
Quickly, directly after the fact, there were the following key publications:
The Vitamin D-lemma – Written by Amy Maxman for Nature, a well-researched news article on the new RDA and the scientific community’s reaction to the new recommendations.
Endocrine Society Guidelines – Michael Holick led a team of vitamin D researchers to publish standards for the Endocrine Society. They were similar to the IOM’s, but with a higher upper limit for adults of 10,000 IU/day.
A Statistical Error in the Estimation of the Recommended Daily Allowance for Vitamin D – The first research paper on the subject, written by Paul Veugelers and John Ekwaru and published October 2014 in Nutrients and explained in this blog.
Canadian and US Petition – Pure North, a non-profit organization in Canada committed to delivering wellness programs, started a petition right away. It now has almost 10,000 signatures.
GrassrootsHealth published Analysis – This analysis, led by Robert Heaney, used D*action data and found, similar to Veugelers and Ekwaru, that the RDA was off by an order of magnitude. Described in detail in this blog.
Comment from the Harvard School of Public Health – by Heike Bischoff-Ferrarri and Walter Willett.
Heaney Interview with Dr. Mercola – Read the recap or watch a 20-minute interview on this topic with Dr. Robert Heaney†.
Vitamin D recommendations in a nutshell
|Institute of Medicine||Endocrine Society||GrassrootsHealth|
|DRI||600 IU/day||1500-2000 IU/day||n/a – test to see|
|Blood level recommendations||>20 ng/ml||>30 ng/ml||40-60 ng/ml|
|Tolerable upper limit||4000 IU/day||10,000 IU/day||n/a|