What Is The RDA Of Vitamin D?
“RDA” stands for “recommended dietary allowance.”
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In the United States, for an adult with, or under, 70 years of age, the recommended dietary allowance (RDA) for vitamin D is 600 IU. If you are over 70, the RDA for vitamin D is set at 800 IU. (1)
However, if you look at a bottle of a bestselling vitamin D supplement, you’ll most likely find a much larger number like 5,000 or 10,000 IU.
This raises two important questions:
- 1Why is there such a large gap between what is officially recommended and what people are routinely supplementing with?
- 2How much vitamin D should you take?
In this article, you’ll learn the answer to this question and the science behind it.
In a Hurry?
At the end of this article you can find a nice summary of the answers to these questions.
How was the Recommend Daily Allowance of vitamin D set?
You may think of the word "allowance" as the name given to the amount of money a parent gives to his child each month.
In the same way, the RDA is an attempt to define the recommended amount of a given substance that you need to give your body, not each month, but each day.
When experts get together to decide what the RDA for a given nutrient will be, there’s one key question on their mind:
“If a person is healthy, how much of this nutrient would she need to take every day to continue healthy?”
Can you feel the weight on their shoulders?
If they get it wrong, healthy people can become deficient in an important nutrient and become unhealthy.
But, if they recommend too high a dose, who can foresee all the potential side effects?
Besides, every body is different. Even two healthy people will have different nutrient requirements based on their genetic makeup, lifestyle and their medical history.
For this reason, researchers tackle the problem in a clever way. They’ll ask themselves:
“What happens when you don’t get enough of a given nutrient?”
Take vitamin D for example.
“What happens when someone doesn’t get enough vitamin D?”
To answer this question researches will learn about the role of vitamin D in the body. This allows them to make predictions.
For example, Vitamin D is essential to regulate calcium metabolism.
“If this is the case,” they reason, “if you don’t get enough of it, your bones should get soft and weak.”
Researches will also look at historical records.
They’ll learn about the children who, due to their lack of vitamin D, would develop rickets.
They’ll crunch all the data and reach an important conclusion:
“If you don’t get enough vitamin D, you’ll definitely develop soft and weak bones.”
In adults, this is known as osteomalacia and is the answer to “What happens when someone doesn’t get enough vitamin D?”
Now, they’re better able to answer their first question:
“If a person is healthy, how much vitamin D would she need to take every day to continue healthy?”
And you already know the answer they’ve reached:
If a healthy adult wants to continue so, he needs at least 600 IU of vitamin D every day, if he has less than 70 years of age, and 800 IU if he is older.
Of course, if you are ill, your health care provider might decide you need a much higher dose. But the point remains:
The board of experts who defined the RDA for vitamin D wasn’t concerned with the specific daily dose an ill patient might need, but rather, with what a healthy individual would require to keep their bones strong.
What about supplement manufacturers?
What questions are they trying to answer when deciding how much of vitamin D they should place in each capsule?
How does a supplement manufacturer decide how much vitamin D should be on the bottles they sell?
When deciding how much vitamin D should be on a capsule, manufacturers ask themselves:
“What do people want?”
To answer this question, manufacturers will gather a team of marketing experts and ask them to research consumer’s habits and wants.
Then, they’ll try and answer this question:
“Is it safe to give the people what they are looking for?”
Answering this question will require consulting with health professionals and a team of lawyers.
For example, suppose their marketing team finds out that people are looking for capsules with 10,000 IU of vitamin D. That’s the answer to their first question: “What do people want?”
Next, they’ll consult with their team of medical and legal experts. “Are 10,000 IU a safe dose?” Why?
Because no company wants to get sued.
If they decide to carry on with the production of capsules with 10,000 IU, then you, the consumer, can rest assure that’s because they believe the profits of selling 10,000 IU capsules outweigh the costs of any potential lawsuits.
And there you have it.
This is the reason for the difference between the amounts defined by the RDA panel of experts and the amounts sold in the form of over-the-counter supplements.
To define the RDA, experts are asking these two questions:
In the case of supplement manufactures, they are asking a set of very different questions:
Who is being evil?
When looking at the values set for the RDA, people might assume these experts were being evil when they decided to set the RDA so low.
Yet, I don’t believe that’s the case.
I believe these researchers were doing their best to answer a specific set of questions concerning the daily needs of healthy individuals who were not deficient in vitamin D to start with.
This means these experts were not evaluating the needs of an individual who might suffer from an autoimmune disorder and who would, therefore, benefit from high-dose vitamin D therapy.
What about manufacturers?
Are they evil in the way they do business?
Only they can know their true ulterior motives. However, the fact that they care about the wants of the people can be a good thing.
Well, without supplement manufacturers, a healthy individual could still get their daily vitamin D needs met by spending a few minutes exposing his skin to the midday sun. No problem there. But what about an unhealthy person?
The high doses of vitamin D required to gain control over an immune system that has gone awry are impossible to get from Sun exposure alone. Moreover, if your body has trouble metabolizing vitamin D in your skin, or in activating it in your kidneys, high-dose supplementation is essential.
Besides, there are manufacturers who employ knowledgeable and caring health professionals who are enthusiastic about the health benefits of the supplements they help create.
For these reasons, whatever the motives behind the entrepreneurs who started supplement manufacturing companies, in many cases, we can be grateful that they did.
Should the RDA for Vitamin D be higher?
As we’ve seen when we analyzed the benefits of supplementing with vitamin D when a woman is pregnant or lactating, supplementing with vitamin D can cut several of the risks associated with pregnancy while also benefiting the developing baby. For example, it can reduce the chances of your child being born with autism.
Also, if you have an autoimmune disorder, or any other health issue that responds well to higher doses of vitamin D, and you have access to a Doctor willing to support you, you should go for the high-dose protocol.
However, since the dosages used in the studies that reached those conclusions have not been widely accepted, it may take some time until the RDA of vitamin D is revised.
Still, there are countries where the RDA is even lower.
For example, when I was researching for the Brazilian edition of my book, I learned that the recommended daily intake of vitamin D by the Brazilian authorities is much lower than in the United States. In Brazil, if you are healthy, you are advised to take only 200 IU of vitamin D per day. (2 – source in Portuguese. Look for page 34).
Will things change?
Nowadays we have a much better understanding of the role of vitamin D in the human body than when the RDA for vitamin D was set, hence my hope that, in the near future, the RDA will be revised and a higher value will be set.
What is the generally accepted safe upper limit of vitamin D intake?
Many vitamin D supplements reflect this consensus that higher doses are safe offering 1,000, 2,000, 5,000 and up to 10,000 IU per gelatin capsule.
If daily doses of 10,000 IU were easily toxic, we can’t imagine these supplements being made freely accessible in most of the world, year after year. Likely, health authorities would have acted to remove them from the market to protect the populations.
Moreover, according to the Vitamin D Council:
"Exposing your skin for a short time will make all the vitamin D your body can produce in one day. In fact, your body can produce 10,000 to 25,000 IU of vitamin D in just a little under the time it takes for your skin to begin to burn" (6)
With this in mind, we are ready to answer a final question:
How much vitamin D should you take daily?
If you are unwilling, or unable, to follow all the safety guidelines associated with high-dose vitamin D, then you shouldn’t be supplementing with doses higher than 10,000 IU per day.
Also, if you are pregnant or lactating, you should be even more careful and only do any supplementation under the guidance of a Doctor well familiarized with vitamin D.
In conclusion, the current RDA set for vitamin D seems to be able to help children avoid rickets while also helping healthy adults to avoid developing osteomalacia. If, however, you are not healthy and perfectly capable of getting all the daily Sun exposure required to maintain your good health, supplementing with 10,000 IU of vitamin D would be a good idea, once you get the green light from a qualified health care professional who is aware of your medical history.