Based on two biomarkers of functional vitamin B12 (cobalamin) status, B12 recommendations formulated more than a half century ago may need to be updated.
How much B12 do we need? Well, the recommended dietary allowance is 2.4 micrograms. 2.4 millionths of a gram every day. That number, I was surprised to learn, was based on a study of just seven people, performed so long ago that four were described as, capital "N" "Negroes". Both society and science have moved on a bit since then, and the new numbers were recently published and it appears "4 to 7" is the new 2.4.
How did they come up with that? Well, two reactions B12 facilitates are the metabolism of methylmalonic acid and homocysteine. And so for B12 deficient these two compounds can build up in our bloodstream because there isn't enough B12 to run these reactions. So low levels of MMA and homocysteine can be a sign of good B12 status.
And as you can see, 2.4 micrograms is good in terms of lowering levels of methylmalonic acid levels and homocysteine but 4 appears to be better. These biomarkers of functional B12 status hadn't even been discovered when quote/unquote "Negroes" walked the earth. And once you hit 7 a day, you basically max out, so there's no need to get more, though there appears to be no danger in doing so; you just pee the excess out.
So that's where they got the new 4 to 7 a day recommendation, though as we'll see, we may need to take much more than that to absorb that amount.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is transcript contributed by Bruce A. Hamilton.
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This is the first of a five-part video series on B12, similar to the series I did on vitamin D where I delve into the derivation of my recommendations, found here for B12 and here in general. To put vitamin B12 in context, please check out Vegan B12 Deficiency: Putting It into Perspective. Tomorrow I'll identify the safest sources of B12. If you can't wait until tomorrow for your NutritionFacts.org video-of-the-day fix, please feel free to check out videos on 1000+ other topics.