A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D (2014)
https://pmc.ncbi.nlm.nih.gov/articles/PMC4210929/
US, nearly 15 times too low
UK, 0ver 22 times too low
IOM calculation
600 units (15 mcg), 97.5% of people will achieve 63 nmol/L
(25.2 ng/ml)
Correct calculation
600 units (15 mcg), 97.5% of people will achieve 26.8 nmol/L
(10.7 ng/ml)
Requirements based on correct calculation
8,895 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 “Average” vs. “Individual” Mistake
Canada studies
Diet gives 232 IU of vitamin D per day
Institute of Medicine (IOM), RDA vitamin D 600 IU per day, (aged 1 to 70 years)
Now called the National Academy of Medicine https://nam.edu/
- UK is even worse. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
- UK, 400 iu or 10 mcg
- 600 iu per day to achieve serum 25-hydroxyvitamin D (25(OH)D) levels of 50 nmol/L or more in 97.5% of healthy individuals.
Levels of 50 nmol/L or more have been shown to benefit bone health and to prevent disease and injury.
The IOM based their RDA for vitamin D on an aggregation of 10 supplementation studies, (32 dose protocols)
carried out during winter months, at locations above 50th parallel
IOM regressed the 32 study averages, dose: plasma ratio
On the basis of this, IOM estimated that 600 IU of vitamin D would achieve an average 25(OH)D level of 63 nmol/L
Requirements based on correct calculation
8,895 IU of vitamin D per day
This dose is well in excess of the current RDA of 600 IU per day and the tolerable upper intake of 4000 IU per day.
The public health and clinical implications of the miscalculated RDA for vitamin D are serious.
With the current recommendation of 600 IU, bone health objectives and disease and injury prevention targets will not be met.
We recommend that the RDA for vitamin D be reconsidered to allow for appropriate public health and clinical decision-making.
The Big Vitamin D Mistake
https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
Explanation of the statistical error
The “Average” vs. “Individual” Mistake
The Institute of Medicine’s goal was to find a vitamin D dose that ensures 97.5% of individual people reach a healthy blood level (50 nmol/L).
The statistical error occurred because the IOM analysed the averages of different studies rather than the data of individual participants.
They looked at 10 studies and took the average blood levels achieved in those studies.
They calculated a statistical range (Confidence Interval) based on those averages.
They found that with 600 IU, 97.5% of the study averages would hit the target.
The Problem
There is much less variation between “averages” than there is between “individuals.”
By using the averages, the IOM accidentally “smoothed out” the data.
They assumed that if the average person in a study was fine, then almost everyone was fine.
The Classroom Analogy
Imagine you want to ensure every student passes a test.
The IOM method
They looked at the average scores of 30 different classrooms. They set a curriculum so that 97.5% of classrooms would have a passing average.
The Reality
Even in a classroom with a passing average, there are students who fail.
The Correction
To ensure 97.5% of students pass, you have to look at the lowest-performing students, not the class average.
The Consequence
When the authors of this paper re-calculated the numbers using the variation of individuals (rather than study averages),
they found that the current RDA of 600 IU does not cover 97.5% of the population.
Instead, it only ensures that 97.5% of people reach a blood level of 26.8 nmol/L (far below the target of 50 nmol/L).
To actually get 97.5% of the population to the healthy target of 50 nmol/L, the math suggests you would need a dose of 8,895 IU per day.