 How much B12 do we need? Well, the recommended dietary allowance is 2.4 micrograms, 2.4 millions 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 has 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 is 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 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 walk 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 4-7 a day recommendation, though as we'll see, we may need to take much more than that to absorb that amount.