Is the Food and Nutrition Board’s recommended daily allowance for vitamin D flawed?

Posted on: November 17, 2014   by  John Cannell, MD

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In 2011 the Food and Nutrition Board (FNB) may have used flawed statistics to recommend a RDA for vitamin D of 600 IU/day for most adults.

The FNB’s statistical analysis showed that 600 IU/day of vitamin D would get 97.5% of the population above 20 ng/ml. They based their recommendations on 10 different supplementation studies that used a total of 32 different doses.

Now two statisticians from the University of Alberta write that the FNB’s statistics were flawed and 600 IU/day will get 97.5% of the population only above 11 ng/ml.

Veugelers PJ, Ekwaru JP. A statistical error in the estimation of the recommended dietary allowance for vitamin D. Nutrients. 2014 Oct 20;6(10):4472-5.

In fact, their analysis of those ten studies showed that 8,895 IU/day are needed to get 97.5% of the population above 20 ng/ml.

The author’s technique was as follows:

“We used 8 studies (using a total of 23 different doses) that had dose response as well as standard deviation and for each of these 23 study dose averages we calculated the 2.5th percentile by subtracting 2 standard deviations from the average. Next, we regressed these 23 values against vitamin D intake to yield the lower prediction limit. This regression line revealed that 600 IU of vitamin D per day achieves that 97.5% of individuals will have serum 25(OH)D values above 26.8 (11 ng/ml) nmol/L rather than above 50 nmol/L (20 ng/ml), which is currently assumed. It also estimated that 8895 IU of vitamin D per day may be needed to accomplish that 97.5% of individuals achieve serum 25(OH)D values of 50 nmol/L or more.”

The authors state:

“The public health and clinical implications of the miscalculated RDA for vitamin D are serious. We recommend that the RDA for vitamin D be reconsidered to allow for appropriate public health and clinical decision-making.”

If their statistics are correct – and I’m not a statistician – I’d say this is a serious error. It is what we call an order of magnitude error, which is a ten-fold error.

1 Response to Is the Food and Nutrition Board’s recommended daily allowance for vitamin D flawed?

  1. hlahore@gmail.com says

    Yes, statistical calculations often remove outliers (data which does not conform)
    Outliers are sometimes considered to be that which is beyond 2 standard deviations,
    This study, however, SUBTRACTS 2 standard deviations from ALL of the data
    Have never seen that done before.
    Seems totally invalid.

    Their calculation of 8,300 IU seems wrong
    Look, for example, at the summary chart of many dose/response studies by Heany in 2013
    http://vitamindwiki.com/tiki-index.php?page_id=3937

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