Germs for Good Health

Although vitamin B12 is found in animal foods it is not synthesized by plants or animals.  Only bacteria make biologically active vitamin B12—animal tissues store “bacteria-synthesized B12,” which can then be passed along the food chain by animals eating another animal’s tissues. Ruminants (like cows, goats, sheep, giraffes, llamas, buffalo, and deer) are unique in that bacteria in their rumens (stomachs) synthesize vitamin B12, which is then passed down and absorbed by their small intestines.  Lions and tigers get their B12 from eating these grazers.

The human gut also contains B12-synthesizing bacteria, living from the mouth to the anus.⁸  The presence of these bacteria is an important reason that disease from vitamin B12 deficiency occurs very rarely in people, even those who have been strict vegetarians (vegans) all of their lives.   The colon contains the greatest number of bacteria (4 trillion/cc of feces), and here most of our intestinal B12 is produced.  However, because B12 is absorbed in the ileum, which lies upstream of the colon, this plentiful source of B12 is not immediately available for absorption—unless people eat feces (don’t gasp). Feces of cows, chickens, sheep and people contain large amounts of active B12.  Until recently most people lived in close contact with their farm animals, and all people consumed B12 left as residues by bacteria living on their un-sanitized vegetable foods.

The human body has evolved with highly efficient and unique mechanisms to absorb, utilize, and conserve this vitamin.  Our daily requirement is less than 3 micrograms a day—one microgram is one-millionth of a gram (1/1,000,000 gram).⁹ Which means, by design, people are expected to be exposed to only miniscule amounts of this essential nutrient. 

Vitamin B12 is the only nutrient that requires a cofactor for efficient absorption.  The cells of the stomach produce a substance, called intrinsic factor, which combines—after the acidic digestion of the food in the stomach—with the B12 released from food.  This “intrinsic factor-B12 complex” then travels to the end of the small intestine (the ileum) where it is actively absorbed. 

There is a second, much less efficient process, called “the passive absorption of B12” which also occurs in the intestine.  This mechanism does not use intrinsic factor and as a result it is 1/1000 as efficient. But by consuming very large doses of oral B12, passive absorption will correct B12 deficiency even for patients with diseases of the stomach and small intestine.

On average, for someone raised on the Western diet, about 2 to 5 milligrams of B12 are stored, mostly in the liver.  This means most people have at least a three year reserve of this vital nutrient. Conservation of B12 by the body boosts the time this supply lasts by 10-fold. After excretion through the bile into the intestines most of the B12 is reabsorbed by the ileum for future use. As a result of this recirculation it actually takes, on average, 20 to 30 years to become deficient after becoming a strict vegan. That is if no vitamin B12 were consumed—which is impossible, even on a strict vegan diet, because of bacterial sources of B12 from the person’s bowel, contaminated vegetable foods, and the environment. 

If you are an otherwise healthy vegan and are using typical dosages of B12 (500 micrograms or more per pill), a weekly dose of this vitamin will be more than sufficient.

You will often find B12 sold under its proper name. Because vitamin B12 contains one molecule of the mineral cobalt, the scientific name is Cobalamin. As a food additive and a supplement pill, vitamin B12 is usually found in the form cyanocobalamin. The effectiveness of this “cyanide complex” for treating neurologic problems has been questioned; therefore, other forms, such as methylcobalamin and hydroxycobalamin may be better choices for the prevention and treatment of B12-related conditions.

Choosing a bioactive form of B12 is important. There are many B12-like substances called analogues found in food supplements, such as spirulina and other algae—these are ineffective and should not be relied upon. Foods fermented by bacteria, such as tempeh, and miso; as well as sea vegetables (nori), have been recommended as sources of B12.  Miso and tempeh do not contain B12.  Nori—the dried green and purple lavers commonly used to make sushi—has been tested and found to have substantial amounts of active vitamin B12 and has been recommended a “most excellent source of vitamin B12 among edible seaweeds, especially for strict vegetarians.