Animal protein is the primary source of B12 in the United States. While fermented foods, nutritional yeast and algae are thought to provide this vitamin for vegetarians and vegans in Third World countries, this does not seem to be true in Western countries with sterile food manufacturing conditions. Vegetarians and vegans in the U.S. and other technologically advanced countries are advised to take a supplement in order to meet their body's B12 requirements.
Primary Sources of B12
Animal protein contains the most significant amounts of vitamin B12. Meat, oily fish like mackerel, herring, and trout, shellfish, egg yolks and dairy products, like live-culture yogurts, are very high in B12. Organ meats, particularly kidney, liver and heart, are especially high in B12.
Fermented Foods
Fermented products, like soy-based tempeh and miso, as well as soy sauce, amasake, pickles, naturally leavened bread or sourdough, nut and seed yogurts and amasake all contain B12 if processed in Third World countries where sanitation is poor and the bacteria rich in B12 are allowed to proliferate. In fact tempeh, which has its origins in Indonesia, has up to 15 micrograms of B12 in a 100-g serving, one of the highest contents of any food. However, in most Western countries, sterile manufacturing environments stops the growth of B12 in fermented foods. When tempeh was first introduced in the U.S. in the 1970s demand gradually grew until, through the mass production of the soy product, the bacteria-to-culture ratio dropped considerably. Thus, mass production and processing methods result in a tempeh that has virtually no B12 content. However, the vital digestive enzymes available from fermented foods may help in the absorption of B12 from other sources and stimulate the growth of B12 bacteria in the intestines.
Nutritional Yeast
Nutritional yeast, which includes brewer's yeast and other varieties of primary yeast, has been a source of B12 for vegetarians since the 1970s. The yeast is either grown in a B12-enriched medium or added later. The former method is better in that the vitamin becomes incorporated into the living yeast. Using nutritional yeast too regularly, however, can lead to overgrowth of the unhealthy candida-type yeast in some people. Also, yeast's high phosphorus content can deplete the body of calcium. Manufacturers have tried to get around this by adding calcium to the yeast. Most yeasts grown on hops, grain and malt pick up many chemicals and alcohol and develop a bitter flavor. Further processing is required to remove this bitterness which subsequently decreases the nutritional value. However, primary yeasts grown on molasses or sugar-beets are naturally pleasant-tasting and require no further processing. These are less common, but are considered the best grade of yeast to buy for nutritional purposes.
Algae
Micro-algae like wild blue-green, spirulina and chlorella were considered the highest food sources of B12 for a long time. However, a more specific testing method known as radioassay has since determined that 80 percent of the B12 content originally reported by past microbiological testing methods is actually B12 analogue which does not have the nutritional properties of true B12. Furthermore, micro-algae taken to treat B12 deficiency does not seem to be effective. It is possible that the greater presence of B12 analogue makes absorption of true B12 difficult. The bottom line, however, is that algae do not seem to satisfy the body's requirement for B12.
Vegetarians and Vegans
Vegetarians and vegans in Third World countries can satisfy their B12 requirements with the microorganisms and bacterial cultures that populate their food. However, in Western countries with sterile manufacturing conditions, vegetarians and vegans who consume no animal products whatsoever, will often require a B12 supplement which is easily absorbed. There have been enough instances of B12 deficiency among strict vegans--children, in particular--to warrant the use of supplements.
Considerations
B12, also known as cobalamin, is required in much smaller amounts than other vitamins: only 1 to 3 micrograms per day. Digestion and absorption need to be good in order to get enough B12. Certain types of medications like antacids and laxatives can reduce stores and absorption of B12. A mucoprotein enzyme produced by the stomach, called intrinsic factor, is required for B12 to be absorbed into the body from the intestines. Suspected B12 deficiency has often turned out to be deficiency of the intrinsic factor. Stomach problems, stomach surgery, stress, aging and genetic factors can all weaken the body's ability to produce intrinsic factor.
References
- "Healing with Whole Foods: Asian Traditions and Modern Nutrition"; Paul Pitchford; 2002
- "Staying Healthy with Nutrition: The Complete Guide to Diet and Nutrtional Medicine"; Elson Haas, M.D.; 2006
