Vitamin B12 is an essential B vitamin, predominately found in animal-derived food products. Plants do not contain significant amounts of vitamin B12, so vegetarians and especially vegans turn to alternative sources to obtain their vitamin B12. For your body to absorb B12 from food, the vitamin must combine with intrinsic factor, a protein the stomach produces. Adults need 2.4 micrograms of B12 per day; pregnant or lactating women need 2.6 micrograms. Consult with your health practitioner to establish doses for infants and children.
Symptoms of B12 Deficiency
Pernicious anemia is an autoimmune condition that affects the stomach lining and leads to a failure to produce the intrinsic factor necessary for proper absorption of vitamin B12. Symptoms resulting from a lack of vitamin B12 include fatigue, weakness, gastrointestinal problems, tingling arms and legs, mouth soreness, loss of balance, irregular menstrual cycles and disorders of the nervous system. Psychiatric disturbances, such as disorientation, irritability, depression, memory loss and dementia, are not uncommon, especially in the elderly who are more susceptible to vitamin B12 deficiency. These serious consequences of B12 deficiency should encourage vegetarians to take B12 supplements and eat foods that contain this vitamin, either naturally or by fortification.
Dairy
Dairy products and eggs are a good source of vitamin B12 for lacto-ovo vegetarians. A cup of non- or low-fat milk or yogurt contains about half the daily requirement of vitamin B12. Vitamin B12 levels in cheese range from 2 to 3 micrograms, depending on the type of cheese you eat. Goat cheese has less vitamin B12 than cheese made from cow's milk.
Plants
There is some disagreement as to whether or not fermented soy products or sea vegetables and algae are adequate sources of vitamin B12, especially for vegans. The University of Maine's 2002 "Teen Vegetarians Fact Sheet for Parents," explains that fermented soy products, such as tempeh and miso, provide some B12 and that shiitake mushrooms, green and blue algae and sea vegetables such as spirulina and nori are good nonanimal sources from which vegetarians can obtain a portion of their daily B12 requirement.
Another opinion is that fermented soy products, mushrooms, algae and sea vegetables contain little or no vitamin B12, despite being marketed as excellent sources of this nutrient. One discrepancy is that these plant products do not contain cobalamin, the active and absorbable form of vitamin B12, but they do contain nonactive analogs of B12. In addition, some products labeled as having high amounts of vitamin B12 are not reliable sources because of the different types of processing used to produce these foods.
Fortified Products
Adults do not need to consume high amounts of vitamin B12. Vegetarians and vegans can fulfill their daily requirement of absorbable vitamin B12 easily by turning to fortified foods. Some boxed breakfast cereals are fortified and supply about 6 micrograms of B12 in each serving, from 1/2 to 1 cup of cereal.
Fortified soy beverages, soy yogurts and tofu also provide vegans and vegetarians with the necessary quantity of vitamin B12 the body needs to maintain balance and health. Meat substitutes are usually soy-based or made from seitan, a wheat gluten product. Many of these foods, including veggie burgers, chicken patties and sausages, are fortified with vitamin B12 and other nutrients. Vegetarian nutritional yeast, brewer's yeast and yeast-derived spreads are rich sources of vitamin B12. If you decide to add a vitamin B12 supplement to your daily regimen, check the vitamin's nutritional facts label to be sure it provides cobalamin, the active form of vitamin B12.
References
- Physicians Committee for Responsible Medicine; Vitamin B12: A Simple Solution; November 2003
- Office of Dietary Supplements: National Institutes of Health; Dietary Supplement Fact Sheet: Vitamin B12; May 2010
- The Dairy Research & Information Center; University of California, Davis; Dairy Goat Milk Composition; John C. Bruhn Ph.D.
- University of Maine; Teen Vegetarians Fact Sheet for Parents; Kathleen Savoie, Extension Educator; 2002
- The Vegetarian Resource Group; Veganism in a Nutshell; 2004
- Agricultural Research Service; USDA National Nutrient Database for Standard Reference, Release 22
