Transcript: Is Vitamin D3 Better Than D2?
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Years ago, it was shown that vitamin D isn’t just the sunshine vitamin for us, but for mushrooms, as well. You take some shiitakes, for example, put them under a sun lamp for an hour, and they make vitamin D—just like we do, lounging at the pool.
Now, most mushrooms you buy at the store don’t have any vitamin D, because they’re grown in the dark. But, there are now sun-bathed varieties on the market that boost significant levels—even now available in sprinkle form. Some mushrooms grown outside in the wild may have some as well—but, only about 12% of one’s recommended daily allowance per cup.
Is the vitamin D in mushrooms bioavailable, though? In 2008, there was a case report of a dark-skinned individual living in England in the winter, who—like the other nine out of ten South Asians living in the UK—was vitamin D-deficient. His physician prescribed a vitamin D supplement; “however, after doing his own research [this] patient decided to self-treat. He bought a UV[B] bulb from a local hardware shop and proceeded to shine this directly onto” two cups of regular mushrooms a day, before stir-frying and consuming them. “He repeated this on a daily basis for 3 months.” And, indeed his vitamin D levels shot up, and he was cured. So, it’s reasonable to assume that such mushrooms may be able to provide a source of vitamin D for those at risk for deficiency. This was only one person, though, so further studies are necessary.
And, finally, those studies have been done. “Bioavailability of vitamin D from [ultraviolet light]-irradiated button mushrooms in healthy adults deficient in [serum 25-hydroxy]vitamin D: a randomized controlled trial.” They compared the mushrooms to vitamin D supplements, to placebo. And, both the mushrooms and the supplements were equally effective in raising D levels, compared to placebo.
The type of vitamin D made by mushrooms, though, is vitamin D2, which is typically derived from yeast, and is the form traditionally prescribed by doctors to cure vitamin D deficiency. Most supplements, though, are D3, which is the type found in plants and animals, and typically derived from sheep’s wool.
Back in 2008, it was established that vitamin D2 was effective as D3 in maintaining one’s vitamin D levels at standard daily doses. Whether folks were given D2, D3, or a combination of half D2/half D3, it didn’t seem to matter much, in terms of improving vitamin D levels in their bloodstreams.
But that was five years ago—what’s the update? Is vitamin D2 better than vitamin D3? It apparently depends on how much you take, and what your starting levels are. Taken daily, in doses up to 4,000 units a day, there appears to be no significant difference in the ability of D2 or D3 to raise vitamin D levels. But, if you take megadoses on a weekly or monthly basis, in doses up to 50,000 units at a time, D3 works better than D2.
And, if you’re not vitamin D-deficient; if your vitamin D levels are normal—for example, you live in California and get enough sun—then D2 from mushrooms or supplements doesn’t appear to raise your levels further.
But, if your levels are fine, why take supplements in the first place? The only reason we care about the levels in our blood is because of the benefits we expect to get from those levels—such as a longer lifespan. The latest Cochrane review on vitamin D and mortality found that while D3 supplementation may be able to reduce mortality, other forms of D (including D2) did not. This may be because most of the D2 trials used megadosing regimens—up to 300,000 units injected into people.
But, you know, until we have good data suggesting D2 supplementation can actually extend one’s life, D3—the type of vitamin D found in animals and plants—may be preferable to vitamin D2, the vitamin derived from fungi.
The best animal to get D3 from is—yourself. But, if you live at a latitude where you’re not able to make enough, then there are both animal and non-animal sources of vitamin D3 supplements.
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