Absorption of Various Forms of B12
Breaking news from 1971 for vitamin B12 junkies!
A reader alerted me to a 1971 study comparing absorption rates of cyanocobalamin, hydroxocobalamin, methylcobalamin, and adenosylcobalamin (1).
They found that at doses of 1 µg, 5 µg, and 25 µg, all forms were absorbed at about the same rate for practical purposes.
However, the researches suggested, based on other research, that at higher doses, cyanocobalamin is better absorbed. They theorized that this could be because absorption of methylcobalamin by way of intrinsic factor is efficient while cyanocobalamin is better absorbed through passive diffusion.
Based on this study, I’ve cleaned up the VeganHealth.org page Methylcobalamin & Adenosylcobalamin where you can also see a table of the absorption rates from this 1971 study.
1. Adams JF, Ross SK, Mervyn L, Boddy K, King P. Absorption of cyanocobalamin, coenzyme B 12 , methylcobalamin, and hydroxocobalamin at different dose levels. Scand J Gastroenterol. 1971;6(3):249-52. | link