The information referenced below is from an article about B12 from the National Institute of Health. You can view the full article: Vitamin B 12.
What is very important in this article is the fact that less B12 is better absorbed. In the paragraph below copied directly from the article, explains that a 50% of a 1 mcg dose of B12 was absorbed compared to only 20% of a 5 mcg dose or 5% of a 25 mcg dose.
“Adams and colleagues (1971) measured fractional absorption of radiolabeled cyanocobalamin and reported that nearly 50 percent was retained at a 1-μg dose, 20 percent at a 5-μg dose, and just over 5 percent at a 25-μg dose. The second of two doses of B12 given 4 to 6 hours apart is absorbed as well as the first (Heyssel et al., 1966). When large doses of crystalline B12 are ingested, up to approximately 1 percent of the dose may be absorbed by mass action even in the absence of intrinsic factor (Berlin et al., 1968; Doscherholmen and Hagen, 1957).”
The article then goes on to say that higher B12 foods are not absorbed as well as lower B12 foods. Although liver is very high in B12, it overwhelms the B12 receptors.
“Absorption from Food. The approximate percentage absorption of B12 from a few foods is presented in Table 9-1. These values apply to normal, healthy adults. No studies were found on the absorption of B12 from dairy foods or from red meat other than mutton and liver. The absorption efficiency of B12 from liver reportedly was low because of its high B12 content.”
We’ve said constantly in the group it is better to eat three to four 1/2 slices of swiss cheese through the day versus trying to eat a high B12 food.
Although excess B12 is not as harming as B6, the question becomes what does our body do with the excess? It is urinated out. Excess urination is not a good thing for those with low blood volume.