Vitamin B-12, how much should I take? How much is too much?
Due to the extensive process required to get B-12 from the diet into the blood and then the cells, which requires adequate stomach acid, intrinsic factor, pepsin and R-binder proteins, pancreatic proteases, and in the blood, transcobalamin II to carry the B-12, it should not surprise you to learn that very little of the supplement of B-12 that you take makes it into the cells. In the book, “Could It Be B-12?”, a quote from a previous NIH document states that, “About 10 mcg of a 500 mcg oral supplement (listed as 8,333% of daily value or DV) is actually absorbed by healthy people“. Taking the standard 6 mcg recommended by the FDA/ RDA would clearly be futile. I would recommend 1000 mcg oral dissolve tabs or lozenges daily and for those with symptoms, I recommend Methyl B-12 shots until symptoms resolve and levels have returned to normal.
The NIH states on its B-12 fact sheet that “Vitamin B12 has not been shown to cause any harm“.
The B-12 fact sheet for professionals states that “undetected and untreated vitamin B-12 deficiency can result in severe and permanent neurological damage“. I feel we must start supplementing with adequate levels during pregnancy, especially for our vegetarian moms and continue to supplement infants.