Vitamin B12

Vitamin B12 is made by bacteria and fungi, but not by yeasts or higher plants. Friendly bacteria resides in large quantities in the gastrointestinal tract of animals and humans. Since the manufacturing site of B12 in humans is not located where absorption occurs, humans can not rely on its availability.

The total vegetarian must find vitamin B12 from other reliable sources.

For the lacto-ovo-vegetarian, reliable sources would include dairy products and eggs that can supply substantial amounts of B12. For example, one cup of milk contains 0.9 micrograms of vitamin B12 while 8 ounces of yogurt has 1.5 micrograms. Sterilized, boiled or canned milk destroys about one half of the vitamin B12. Since most of the vitamin B12 resides within the cholesterol-laden yolk, it would be better for the lacto-ovo-vegetarian to rely on low-fat dairy products for their source of B12. Vegetarians who use B12 supplement should ensure that it contains an active form of the vitamin - namely, cyanocobalamin or hydroxocobalamin.

There is another story for vegans. Fermented soy products, such as miso and tempeh, shiitake (dried mushrooms) and algae such as spirulina and nori contain practically no vitamin B12. While these foods are often sold in health food stores as "excellent sources of B12" and are widely used by the macrobiotic community, they actually contain little, if any active B12 (cobalamin). Instead they contain analogues of B12 that are not active and may actually block the absorption of true vitamin B12. Vegans who previously ate animal-based foods may have vitamin B12 stores that will not be depleted for 20 to 30 years or more.

Since there isn't a reliable and adequate source of vitamin B12 in plant foods, total vegetarians should obtain their dietary needs from either foods fortified with B12, such as some fortified, ready to eat cereals, fortified soy beverages, fortified meat analogues, or from the regular use of vitamin B12 supplement. A B12 supplement of five micrograms taken daily is probably adequate. Some suggest that B12 supplements should be thoroughly chewed for better absorption. As mentioned earlier, the B12 supplement for the total vegetarian should include an active form of cyanocobalamin or hydroxocobalamin. Seaweed and soy products do not contain significant levels of active B12 despite the claims made for such products. The basis for the erroneous claims stems from the fact that the method that is often used to measure B12 does not distinguish between the active and inactive forms of the vitamin.

To prevent the risk of psychiatric problems and permanent neurological damage, a total vegetarian who avoids all animal products should have their serum B12 levels checked periodically. Total vegetarians who are pregnant should routinely have their serum B12 levels checked. Anyone found to have a serum B12 level below 300pg/ml should be tested for urinary methylmalonate levels.

The General Conference Nutrition Council recommends the total vegetarian should include fortified food high in vitamin B12 supplement.