How Much Vitamin D Is Right For You?

From the recommended dose to 'mega doses'—is it possible to get too much vitamin D? What's the best way to determine the right dose for your unique nutritional needs?

3 min read

How Much Vitamin D Is Right For You?

Why are we seeing vitamin D pills with doses ranging from 1,000 to 10,000 IU even though the National Academy of Sciences suggests consumption of only 400 to 800 IU of vitamin D daily?

In the early days following discovery of vitamin D in 1922 by Edward Mellanby, just 400-600 IU was deemed to be sufficient to prevent rickets (bone softening) in growing children. However, there are many health benefits to vitamin D besides preventing rickets. More vitamin D is needed to optimize the immune system.

"The Big Vitamin D Mistake"

In a report entitled “The Big Vitamin D Mistake” published in the Journal of Preventive Medical Public Health in 2017, it was revealed that the number of excess deaths from all diseases falls dramatically at blood levels of Vitamin D that exceed 100 nanomoles per liter of blood. To achieve that level, breast fed infants would need 1500 units of vitamin D, children over age 1 would need 3000 units, and young adults around 8000 units per day!  It takes 8895 units of vitamin D for 97.5% of adults to achieve the 50-point level. So now it’s just a matter of how healthy you want to be.    

When Dr. John Cannell founded the Vitamin D Council in 2003 to educate the public about “the sunshine vitamin,” many Americans thought they were getting enough vitamin D from fortified milk and were hesitant to take vitamin D pills that appeared to provide mega-doses. 

Can you get too much vitamin D?

But then it became evident that someone standing in the midday summer sun would make about 10,000 IU of vitamin D in an hour (your body produces vitamin D when the sun’s rays convert cholesterol into the vitamin). And no one is known to have developed vitamin D poisoning from spending an hour in the sun. So, fears of an overdose subsided. And these days, with the recommendations for sunscreen cutting out the amount of vitamin D people make naturally, that 10,000 IUs from being outside for an hour is pretty much out of reach.

And then there are the doctors who inject 300,000 units of vitamin D at one sitting into older women for wintertime bone protection without side effects. Suddenly, it becomes apparent that 400 IUs of vitamin D is a mere drop in the bucket.

In 1998, researcher Reinhold Vieth reported that supplemental intake of 400 IU vitamin D/day barely elevates blood levels, raising them by only 7 to 12 points. To achieve a desirable range of 50 to 80 nanomoles per liter requires an intake of approximately 2100 IU vitamin D per day.

More is better but excessive mega-doses are stored in the liver, can crowd out vitamin A, and may produce side effects if blood levels go over 150. Mega-doses taken over a long time can (rarely) produce headaches, fatigue, frequent urination, nausea, vomiting, poor appetite, and constipation—but these are reversible symptoms.

How much vitamin D is right for you?

The bottom line is, when you read the Supplement Facts box for 5000 IU vitamin D supplements and it says you are getting 625% of the recommended Daily Value, that is not an overdose.  For most adults, 5000 IU achieves desirable blood levels. And balancing vitamin D with co-factors such as zinc, vitamin K, magnesium, and boron makes for an ideal vitamin D supplement. These nutrients work together with vitamin D for a host of benefits including bone health, immune system function, cardiovascular integrity, and more.

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Purity Products

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