The Real RDA for Vitamin D Is 10 Times Higher Than Currently Recommended

Story at-a-glance

  • The Institute of Medicine’s (IOM) recommended dietary allowance (RDA) for vitamin D underestimates the need by a factor of 10, due to a mathematical error
  • IOM posits that a vitamin D serum level of 20 ng/ml is adequate, but many researchers believe that is too low; 20 ng/ml has been shown to be inadequate even for prevention of osteomalacia
  • To ascertain your ideal dose, you need to test your vitamin D level. Aim to get above 40 ng/ml, and take whatever dose you need to reach and maintain that level


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

Without a doubt, one of the most important nutrients for optimal health is vitamin D. But questions still remain about just how much is needed. Dr. Robert Heaney M.D., is one of the premier vitamin D researchers in the world.

He's also the research director of GrassrootsHealth, headed by Carole Baggerly, which is compiling data from a number of population-based studies like the D*Action project, which many of my readers are participants in.

What is clear is that the recommended dietary allowance (RDA) should really be 10 to 15 times what the Institute of Medicine (IOM) recommends.

Trained as a clinical endocrinologist, Dr. Heaney has spent a large part of the last 50 years doing clinical research; most of it in the field of vitamin D, working on quantifying the vitamin D economy.

This includes defining how much vitamin D is necessary to reach a certain effect, how large of an effect you might get at a particular dosage, how much vitamin D you make in your skin in response to sunlight, and how long it lasts.

"It's the amounts coming in and out and the balance you have that really is important," he says. "That's where I've been focusing my work most of these past 25 years." 

Current Recommendations Are Inadequate Due to Flawed Math

As noted by Dr. Heaney, there are two issues with respect to the IOM stance on vitamin D requirements:

  1. Did they select the appropriate number as an indication of adequacy? The IOM chose 20 nanograms per milliliter (ng/ml) of serum concentration of 25-hydroxy vitamin D as an adequate level, but many vitamin D researchers believe that's too low
  2. To maintain a level of 20 ng/ml, the IOM says you need to take 600 IUs a day up to age 70, and 800 IUs if you're over 70

According to Dr. Heaney, the second statement is flat wrong, as it's the result of a mathematical error.

Last year, two investigators from the University of Edmonton published a paper1 in the journal Nutrients, which explicitly showed that the IOM had made a calculation error in defining the intake needed to reach and maintain 20 ng/mL. Had the IOM calculated it correctly, the RDA would have been at least 10 times greater than what was publically posted. 

"The recommended dietary allowance, as I think most of us know, is the intake that is reckoned to be necessary to meet the nutritional need of 97.5 percent of the population...

How much is enough? The Institute of Medicine said 600 IUs was enough. But what's very clear is that 600 IUs would not get 97.5 percent of the population above 20 ng/ml. That's what the Edmonton investigators showed.

As a matter of many as half of the people getting 600 international units a day wouldn't get up to 20 nanograms per milliliter... The Edmonton investigators calculated a number of 8,895 IUs per day, using the same set of studies on which the IOM had based its calculation...

When I was able to access the GrassrootsHealth (GRH) data, a completely different set from the one used by the IOM, we could directly calculate the intake needed… 

That's because, in the GRH database,we know exactly how much of an increase in 25-hydroxy D the participants got on whatever dose they were taking. Our calculation showed that about 3,800 IUs per day, in addition to everything they were already getting [from sun and food], would have been necessary to get 97.5 percent of that population to 20 nanograms per milliliter. 

Factoring in the basal intake in the GRH population, we showed that you need about 7,000 international units per day in order to get 97.5 percent above 20 nanograms per milliliter. That's very close to the figure that the Edmonton investigators had used: 8,895."

You May Also Need a Higher Level of Serum Vitamin D Than Currently Recommended

As for a more precise dosage, more and better studies are needed. But what is clear is that the amount needed to get most people above 20 ng/ml is at least 10 times higher than what the IOM recommends, and their own data shows that as well, were it only calculated properly.

Dr. Heaney and colleagues recently challenged the IOM's vitamin D recommendation,2 stating the RDA underestimates the need by a factor of 10. Most vitamin D experts also agree that a serum level of 20 ng/ml is too low for optimal health, which means the requirement for most people is even higher than that.

GrassrootsHealth, for example, believes a vitamin D level of 40 ng/ml is a more appropriate minimum level. According to Dr. Heaney, the evidence shows that 20 ng/ml is not even adequate for the prevention of osteomalacia.

"The point is the Institute of Medicine is dead wrong; not because it chose the wrong number, but because it made a mathematical mistake. They miscalculated, which is really kind of embarrassing if you think about it. Somebody didn't check the work," Dr. Heaney says.

"Now, having made that mistake, bureaucrats being bureaucrats, they're unlikely to want to change. They're not going to say, 'Oops, we made a mistake. Here is the right answer.'

They seem to say, 'No, we did the right thing. We are not wrong, [and] if no federal agency asks to have it reviewed, it could be 10 years from now before anybody ever looks at it again.'"

Flawed Recommendations Have Far-Reaching Consequences

Fortunately, vitamin D is sold over the counter as a supplement, and both you and your physician are free to disregard what the IOM says. However, the IOM's RDA does affect certain government programs, such as military meals, meals for the elderly, and the school lunch program.

It's also used as the standard for Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). So there still are profound ramifications to the whole nutritional establishment of the United States. Canadians are also affected by the IOM's mistake.

Canada jointly funded the effort of the IOM, and a particular problem for them is found in the First Nations people living in the Northern Tier of territories. In years past they had lived off of marine products such as oily fish, seals, and whale blubber – rich sources of vitamin D. They have now converted to more industrialized nation food sources that are poor in vitamin D.

In those Northern territories there's also not enough sun to make sufficient vitamin D for yourself. So Canada is now faced with an epidemic of rickets and osteomalacia in the Northern Tier of its territories, and giving people 600 IUs simply isn't going to be enough, yet that's all that's being recommended.  

A recent paper from the Netherlands showed that giving people who were demonstrably vitamin D deficient 800 IUs of vitamin D per day resulted in less than half of them reaching 20 ng/ml.

"Here is a controlled trial providing exactly what the Institute of Medicine said for people over age 70, and yet it didn't work. It didn't produce the result the Institute of Medicine had said. The reason it didn't, of course, is it doesn't work. The Institute of Medicine had calculated it wrong. I cannot stress that too strongly. They made a mathematical error."

Focus on Your Blood Serum Level, Not the Dose

While most people want to know what dose to take, it's important to realize that there can be vast differences in the response to any particular dose from one person to another. So the focus should not be on the dose, but rather on how high your 25-hydroxy D level gets on a particular dosage. "I want mine to be above 40 nanograms per milliliter," Dr Heaney says. "If it didn't get above that on my starting dose, then I have to take more. It's just that simple."

There's little risk of toxicity even at higher blood levels. In fact, research3 shows you have to get well above 200 ng/ml before there's any risk of toxicity, and the risk even then is low. There is no risk of toxicity below 200 ng/ml.

So 200 ng/ml is the threshold for toxicity, and 40 ng/ml is the lower threshold for therapeutic activity, and the threshold thought to protect the health of the general population. That said, if you're using vitamin D as a pharmacologic treatment under the guidance of a physician for a medical disorder, you can go far higher.

I typically recommend a level between 50-70 ng/ml for optimal health and general disease prevention, and 70-100 ng/ml as an adjunct to the treatment of heart disease and cancer. According to Dr. Heaney, "the sky is the limit there; so long as he or she knows what he or she is doing, there will be no problem."

It's worth noting that a common issue impairing your liver's ability to produce 25-hydroxy D is non-alcoholic fatty liver disease (NAFLD), possibly aggravated by excess fructose consumption. NAFLD is associated with obesity, but excess visceral fat in and of itself does not store away vitamin D, thereby increasing your vitamin D requirement. The reason for this is because most people get their input vitamin D 25-hydroxylated so rapidly that there's no native vitamin D left over to store in fat.

The only time you begin to store vitamin D in fat is when you've saturated your liver's ability to make 25-hydroxy D. At that point, vitamin D starts backing up in your blood because it can't be 25-hydroxylated quantitatively. "When it begins to rise in your blood, it diffuses into fat. But that doesn't happen at doses of less than 50,000 IUs per week, which means that there is not very much fat storage in most of us," Dr. Heaney says.

vitamin d levels

Take Control of Your Family's Health with Vitamin D Testing

Many families have seen a rise in the proportion of their income spent on healthcare expenses. For many, the costs now exceed what they spend on food. Measuring your vitamin D performance and taking steps to optimize your level is one of the easiest and least expensive things you can do for your health, and could help you rein in out-of-control health care expenses.

GrassrootsHealth D*Action is an integrated set of performance and feedback systems to give you complete control of your individual vitamin D performance systems, which will help you gain a total picture of your health.

Vitamin D Kit
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There's no doubt in my mind that the D*Action programs can be a major key to help turn the current health paradigm from "treatment" to "prevention." It's exciting to consider that, within our lifetime, we may be able to prevent the majority of breast cancer, for example.

The D*Action Breast Cancer Prevention project began in 2012, and is a major step in that direction. While it still needs a few more years' worth of data to be complete, the women enrolled in the project are already exhibiting fewer cases of breast cancer than would be expected within the general population. To learn more about this breast cancer prevention project, please see this previous article. (Women 60 and over with no current cancer or current treatment are eligible for the breast cancer prevention study. You can sign up here if you're eligible.)

Optimizing Vitamin D Is One of Your Most Cost Effective Health Strategies

Remember, you're not bound by the IOM's mistakes, miscalculations, and flawed recommendations. You can take 8,000 IUs of vitamin D a day, or more, if that's what you need to reach and maintain a level of at least 40 ng/ml. Vitamin D exerts epigenetic control of thousands of genes, and can vastly decrease your risk for heart disease, cancer, osteoporosis, osteomalacia, and much more. It's a profoundly important nutrient that has massive health benefits.

Just remember that when you take oral vitamin D, you also increase your need for vitamin K2. Vitamin D also need sufficient amounts of magnesium and zinc to work properly, and is best taken with some healthy fat, as it's a fat-soluble vitamin.

Also make sure your children have adequate vitamin D levels—especially during the first year of life. If you're pregnant or planning a pregnancy, get your vitamin D levels checked and make sure your vitamin D level stays within an optimal range, because your baby needs it during the developmental phase in utero as well. As noted by Dr. Heaney:

"It's never too late to start, but it's never too early to start either. It's now becoming increasingly clear that there are midlife and late-life consequences of infancy vitamin D deficiency, and it is heartbreaking to see us ignoring this relationship. We need adequate vitamin D status in infants at a time when they are sorting out the immune system... If they don't get that right, they are subject to the various autoimmune disorders from type 1 diabetes to multiple sclerosis.

It's also recently been shown that women in their child-bearing years are more prone to preeclampsia [if they hadn't received sufficient ] vitamin D in the first year of their own lives. It's mind-shattering to realize that early life behavior has consequences later in life that are dreadful and expensive."


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