Millions of Americans are harming themselves right now because of a simple mistake about vitamin D. Are you one of them? Back in 2011 when the Institute of Medicine (IOM) last updated the vitamin D RDA, they made a simple, but serious statistical error in their estimation of the RDA. In this blog I will break down the statistical mistake they made, why it matters, and how correcting this simple error could dramatically improve public health.
Article Summary:
Millions of Americans are not getting enough vitamin D due to a major mistake in the recommended daily allowance (RDA) set by the Institute of Medicine (IOM) in 2011. The mistake was discovered by researchers Paul Veugelers and John Paul Ekwaru. They showed that the data for calculating the RDA was analyzed improperly. Instead of an RDA of 600 IU/day, it should have been about 8,000 IU. A second group, led by Robert Heaney and Cedric Garland, confirmed this finding, showing that 8,000 to 10,000 IU/day is likely needed for most people to reach healthy vitamin D levels, reducing the risk of bone diseases, autoimmune disorders, infections, and chronic diseases. Get your vitamin D tested and adjust your intake accordingly.
Where Did It All Go Wrong?
Back in 2011, now 13 years ago, the Institute of Medicine (IOM), our official governmental body that establishes standards for nutritional intakes among other things, published the latest RDA for vitamin D. The RDA for adults is 600 IU, up from a previous level of 400 IU. The aim in setting the RDA at 600 IU was that this would ensure that 97.5% of the population would achieve serum 25(OH)D levels at least 50 nmol/L (20 ng/ml). Serum 25(OH)D levels above this were seen to be protective of bone health. (The study group that reviewed the scientific literature did not consider any other outcomes for vitamin D except bone health, which is a mistake to be discussed in another blog.)
Anyways, their goal was to get everyone in the country out of frank deficiency of vitamin D and get them all above 50 nmol/L (20 ng/ml).
In 2014 Paul J. Veugelers and John Paul Ekwaru, two researchers from the School of Public Health at the University of Alberta, published their findings of a statistical error in the estimation of the RDA for vitamin D. The mistake was a simple one that many a beginner in statistical analysis has made. It isn't clear why this mistake was not discovered before publication of the RDA in 2011, not why no action on the mistake has been taken since 2014.
In order to see the mistake I will put the original graph from the IOM's calculations, and then the corrected figure from Veugelers and Ekwaru.
So, what we see in Figure 1 is the relationship between intakes of vitamin D and the resulting serum levels of 25(OH)D. The researchers found the averages, shown in green diamonds, from 32 intakes published in 10 different studies. They then calculated the expected average and the 95% confidence intervals, shown in the dark green line in the middle and the dotted lines above and below the data.
On the basis of this data the IOM estimated that 600 IU of vitamin D would get everyone above the dotted lower line at 50 nmol/L of 25(OH)D. And that right there is the basis for the 600 IU intake of vitamin D, shown in the cross-hairs in Figure 1.
But Veugelers and Ekwaru pointed out, correctly, that this is not a correct interpretation of the data. When the IOM took the regression on the averages, the confidence level just indicates the likelihood of the average of the population would be above 50 nmol/L. This is very different from saying that every individual in the population would have a serum level of 25(OH)D above 50 nmol/L.
The Re-Analysis of the Data
So, Veugelers and Ekwaru took the exact same data that was used by the IOM and estimated how much vitamin D is needed to achieve 97.5% of the population having a 25(OH)D level above 50 nmol/L (20 ng/ml). For the 23 study averages that also reported standard deviations they calculated the concentration of 25(OH)D at 2 standard deviations below the average, shown as yellow dots in Figure 2. This covers 97.5% of the population at the lower end. They then calculated the regression line, shown as the dashed red line in Figure 2, for these lower limit estimations.
The result, as you can see in Figure 2, is a line that is much lower than the original line by the IOM. In the IOM's analysis only the average of the population would fit in between the dashed green lines, but many individuals would have levels far outside of this zone. And indeed, that is what has been found since then as well.
What the re-analysis says is that 600 IU a day only guarantees that 97.5% of individuals will have a 25(OH)D level of 26.8 nmol/L (10.7 ng/ml), which is just above frank deficiency. Furthermore, the authors extrapolated the data to show that to achieve a 97.5% of individuals to have a level above 50 ng/ml the intake would have to be 8,895 IU of vitamin D per day. This was only a gross estimate as the data did not test intake levels anywhere near that amount.
Confirmation of the Result: The Current RDA is Way Too Low
While one analysis did show the error, scientific progress is made when other people confirm another person's work. And that is exactly what happened here. Robert Heaney and Cedric Garland and a group from GrassRootsHealth put together an analysis using a completely different data set. GrassRootsHealth encourages people to do testing of vitamin D levels and they have compiled de-identified data between people's intake of vitamin D and their 25(OH)D test results. These data are not so carefully controlled for keeping out sunshine, taking the test in the winter and so on. There are real life data points here. And there are individuals here in this data set that took as much as 10,000 IU of vitamin D on a daily basis.
So, what do we see?
The blue regression lines are the best fit for the average response to taking vitamin D. (Note the vertical scale is in ng/ml rather than nmol/L as in Figures 1 and 2. To convert nmol/L to ng/ml divide by 2.5.) The red line above and below are the 95% confidence limits for the entire cohort. The 3 dashed green lines are for 20, 30 and 40 ng/ml. Where they cross the red line is the lower limit of vitamin D intake to ensure all (95% at least) the people in the entire population would have a serum 25(OH)D result of 20, 30 or 40 ng/ml. Sounds complicated?
So, for everyone to be above 20 ng/ml (which is the level chosen by the IOM for setting the RDA) Figure 3 shows the intake level to be 3,875 IU of vitamin D per day. Now, this number doesn't take into account sunshine or any other sources. But even near zero supplemental input (the Y axis) people have a 25(OH)D level above 0, actually at 34 ng/ml on average. To get this level you need about 3,000 IU of vitamin D every day from sunshine and food. So, the amount of vitamin D that you need from all sources (which is what the RDA is) is actually the sum of their supplement, food and sunshine combined. This comes out to about 7,000 IU of vitamin D per day, which is close to what was seen by Veugelers and Ekwaru. Confirmation!
But you could make a great argument that 20 ng/ml is not really enough. 40 ng/ml might be closer to the bottom level of truly acceptable levels of vitamin D. And to get to that level this population had to take 9,122 IU/day. Plus about 3,000 from sunshine and other food. So, over 10,000 IU/day of total intake of vitamin D to get everyone in the population above 40 ng/ml of 25(OH)D.
So, these two different analyses both point to the RDA being drastically too low, as in 10-fold too low at least. Let that sink in. The RDA for vitamin D is only about 10 percent as much as it should be. 5,000 IU/day of vitamin D no longer seems so radical, and 10,000 IU/day seems like quite a good idea for many people.
The Hidden Costs of Inadequate Vitamin D
In addition to strengthening bones and preventing osteoporosis, vitamin D has a very important role in helping people fight acute infections, reducing the risk of auto-immune disorders, and enabling people to resist chronic diseases.
In a real-time analysis of 325 vitamin D studies with Covid-19 vitamin D reduces risk with very high confidence for mortality, ICU admission, hospitalization, recovery, cases, and viral clearance. Currently (Oct 2024) there are 122 vitamin D treatment for COVID-19 studies, showing 36% lower mortality [28‑43%], 19% lower ventilation [-3‑36%], 45% lower ICU admission [28‑58%], 19% lower hospitalization [9‑29%], and 17% fewer cases [9‑24%]. While there are many treatments that are effective for early treatment of viral infections, vitamin D stands out as a cheap, simple way to reduce your risk of serious viral infection complications. How many lives were lost due to not having enough vitamin D in their body?
If you thought that statistics were not important, I just showed you a case where proper statistical analysis matters a great deal. Millions of people following the IOM's advice to only take 600 IU of vitamin D instead of more than 6,000 IU have much increased death from all causes, including COVID-19, and a lot of pain and suffering from heart disease, diabetes, and autoimmune diseases that could have been improved with higher levels of vitamin D. Vitamin D does a lot more than just keep your bones strong.
Revisiting the RDA: How Much Vitamin D Do You Really Need?
So, how much vitamin D do you need? The total amount you need is likely 8,000 to 9,000 IU per day. 10,000 IU per day is not an unreasonable amount for many people. Some of this may come from sunshine or fortified foods. If you get a lot of sunshine near noon at latitudes near the equator on a large portion of your skin, you may be fine with just sunshine exposure. For those living in the upper part of the northern hemisphere, you probably need to take some supplements when you can't get that kind of sunshine exposure, like 8-9 months of the year.
How to Ensure You Are Getting Enough Vitamin D
Figure out how much vitamin D you currently getting from your diet and supplements. Then get a blood test for 25(OH)D. The result you are looking for is in the range of 50-80 ng/ml for optimal health. A recent meta-analysis of vitamin D trials found that the data strongly suggests that maintaining serum 25(OH)D concentrations of more than 50 ng/mL is associated with significant risk reduction from viral and bacterial infections, sepsis, and autoimmunity. So, get tested and then adjust your supplemental intake accordingly to get into that range. You may want to consider our Vitamin D3 / K2 supplement. It supplies 5,000 IU of vitamin D3 and 2 forms of vitamin K2 to ensure that the increased calcium absorption goes to the right places. If you want to know more about why you should take vitamin K2 with your D3, check out this article.
Conclusion
What seems to be a minor statistical error turned out to be a huge public health blunder. But don't hold your breath for the IOM to fix its mistake. Take control of your own health. Get your vitamin D level tested every year and make sure your 25(OH)D level is in the range of 50-80 ng/ml. It is likely that you need between 8,000 and 9,000 IU of vitamin D every day to get there, but individualized testing will inform your decision as to how much you need.
