Your need for vitamin B-12 is the same whether you're a vegetarian or a carnivore, but if you're a strict vegan, your opportunities for obtaining B-12 are limited. Vegans do not eat any animal-based foods. Even honey, produced by insects, is not a strictly vegan food. The vitamin B-12 is synthesized by microbes, not plants, and thus does not jibe with a strict vegan philosophy. Yet this nutrient is essential to health, even the health of strict vegans.
Functions of B-12
Your red blood cells need B-12 to develop properly. Lack of B-12 can lead to megaloblastic anemia, a condition wherein red blood cell production declines and immature, abnormally large red blood cells are produced. B-12 is also needed to keep your nervous system functioning, and B-12 deficiencies are associated with damage to the myelin sheath, an insulating layer that covers nerve cells.
The average person over the age of 14 needs to consume 2.4 micrograms of B-12 daily to maintain red blood count and protect the nervous system. If you're pregnant, you're advised to consume 2.6 micrograms of vitamin B-12 each day. For lactating women, the recommended intake of B-12 is 2.8 micrograms. You can take supplemental B-12, either on its own, as part of B-complex vitamin, or in a multivitamin. B-12 is not known to have toxic or adverse effects in high dosages, and no upper intake limit for B-12 has been determined by the Food and Nutrition Board, according to the Linus Pauling Institute.
Vegetarian Sources of B-12
Vegetarians who eat dairy products and eggs can obtain enough B-12 through responsible consumption of those foods. For instance, a cup of plain, low-fat yogurt contains 1.37 micrograms of B-12 -- about half your daily requirement. A cup of skim milk contains 1.23 micrograms. A single large egg delivers .45 micrograms of B-12. The ample amount of B-12 in these foods makes it easy for ovo-lacto vegetarians, meaning those who east eggs and dairy products, to consume adequate amounts of B-12. Vegans must rely on foods fortified with B-12 to meet their dietary needs. Fortunately, B-12 is added to many cereals, grains and nutritional yeasts. Read the labels on food products to determine whether they've been fortified with B-12.
If you aren't consuming enough B-12, it can take years for the symptoms of deficiency to become apparent. Your liver stores enough to last up to 5 years. Once these stores are depleted, however, you may experience the fatigue and weakness associated with megaloblastic anemia, or the tingling in your hands and feet associated with nerve damage. Nerve damage from B-12 deficiency can become permanent if it is not treated in time. Cognitive disorders, such as dementia, can also result from B-12 deficiency.