Why the current vitamin D recommendations may be too low, other expert recommendations may be too high, and 2000 international units a day may be just right.
Image thanks to plant nutrition.
Is there a way we can ask the body how much vitamin D it wants overall? Scientists came up with two ways. First, let’s say you give a whopping dose, and I mean whopping, 100,000 IUs, something that could be toxic if done on a daily basis. The question is, what’s your body’s saturation point. Of this massive dose much does your body actually use, and how much does it sock away in storage at for use later on down the road? Here’s the graph; 30 people followed for 4 months after the megadose. Here’s the flood of D coming into their system, but the solid circles represent the pool of vitamin D our body is keeping in our blood stream for activation, and the rest is likely stored away to be used on an as needed ongoing basis. Note that in this setting of abundance the body is keeping our levels right around that sweet spot dip found in the U-shaped mortality curve.
You can do the same thing at the other end of the spectrum too. Instead of a megadose you can start by giving really tiny doses and gradually work your way up. When you do you get a graph like this showing a so-called biphasic pattern, really steep at first, but then leveling out.
When you take in just a little bit, your body zips it into circulation, desperately needing it. But then as you increase the dose, at a certain point you kind of turn the corner when the crisis is averted, your body seems happy enough with your levels that as you take more your levels still rise, but it’s not such an emergency.
Now if this plateau was flat, completely horizontal there’s be no risk of toxicity, but because your body can’t help but let some in, your levels continue to rise with increasing intake and you can run into vitamin D toxicity problems if we take too much. But what’s this level here, right at the corner, when your body takes a big sigh of relief that you’re doing pretty good on vitamin D?
Working in from both ends, the level at which your body appears satisfied translates to about 2000 IUs a day, which should get us right into that U-shaped longevity sweet spot, whereas the Institute of Medicine recomendatiosn appear too low, and the 10,000 recommendations put forth by others appears too high.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by veganmontreal.
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Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. This is the 8th video in a nine day series on vitamin D. Be sure to check out yesterday's video-of-the-dayHow the Institute of Medicine arrived at their vitamin D recommendation.
For some context, please check out my associated blog posts: Vitamin D: Shedding some light on the new recommendations, Eating To Extend Our Lifespan, and Vitamin D from Mushrooms, Sun, or Supplements?