Vitamin B12 in Vegetarian and Vegan Diets
Sources, Supplements and Deficiencies of Cobalamin in Meatless Diets
Oct 29, 2008
Vitamin B12 is a large, complex vitamin found only in foods that come from animals. It is the largest B-vitamin, which makes it difficult for the body to break down and absorb.
Because Vitamin B12 has a cobalt molecule at its centre, it is sometimes called cobalamin or cyanocobalamin.
Food Sources of Vitamin B12
Vitamin B12 is found in dairy products, meat, fish and eggs. It is not usually listed on nutrition labels.
Vegan diets contain minimal and difficult-to-measure amounts of B12. Small amounts of the vitamin may be absorbed from algae or the bacteria on food. Some vegan foods are also fortified with vitamin B12.
Vitamin B12 is bound to the protein in animal foods and must be broken down in a stepwise process. Specialized cells begin this process in the stomach. How much of the vitamin B12 we eat is absorbed depends on factors like pH and the presence of the receptors that allow the vitamin to be absorbed.
Vegan Vitamin B12 Supplements and Fortified Foods
Vegan food products may contain added vitamin B12. Fortified soy beverages and fake meats (meat analogs) have added cyanocobalamin, as do certain brands of fortified nutritional yeasts and cereals. Be cautious about relying on a single source of vitamin B12 and read labels when information is available.
Vitamin B12 supplements are available and most are vegan. Some combination iron and vitamin B12 products may be derived from animal products. Check the label to ensure supplements are acceptable for a vegetarian or vegan diet if this is a concern. Speaking with a Registered Dietitian who is familiar with vegan diets can help in selecting the right supplement for each individual.
Vitamin B12 Roles in the Body
Vitamin B12 is essential to making the red blood cells that carry oxygen in the body. It also helps to form some amino acids, which make up body protein and DNA. Vitamin B12 also helps to release energy from foods.
Vitamin B12 Deficiency
A B12 deficiency has serious consequences. It may start with anemia (which is reversible), but progresses over the long-term into neurological (spinal and brain) symptoms like memory loss and dementia. Developing these serious symptoms may take up to seven years of deficiency, but once they are present they are irreversible. For this reason, it is important to maintain a consistent supply of vitamin B12 in the diet.
Who is at risk for deficiency?
- Vegans generally have a low intake of vitamin B12. Those who avoid animal products are at risk risk for deficiency. Lacto-ovo-vegetarians (who eat dairy products and eggs) are not as likely to be deficient.
- As we age, we produce less gastric (stomach) acid and fewer of the specialized molecules required to absorb vitamin B12. As a result, older individuals may gradually lose the ability to absorb vitamin B12 from the diet.
- Breast-fed infants of vegan mothers are at risk if no supplements are taken. Always check with a doctor regarding nutritional needs during pregnancy.
Recommended Dietary Allowance of Vitamin B12
Adults need 2.4 micrograms (mcg) of vitamin B12 per day – a very small amount. Children need less than this (0.9 mcg day for ages 1-3; 1.2 mcg day for ages 4-13).
The level of B12 added to vegan foods varies: some soy beverages are not fortified at all, while others contain 50% of an adult's daily need in one cup. A large fresh egg contains 0.65 mcg and one cup of whole cow's milk contains 1.07 mcg. To look up how much B12 is found in a food, search for it in the USDA's Nutrient Database.
Selected Reference:
Health Canada Compendium of Monographs - Vitamin B12.
