Vitamin B-12 is necessary for the proper growth and development of your body's red blood cells. Pernicious anemia, a disease that was fatal before 1920, can result when the body does not absorb enough vitamin B-12. It was discovered that pernicious anemia could be cured by eating large amounts of liver, and later it was found that liver contains both vitamin B-12 and a substance (intrinsic factor) which your body requires to effectively absorb vitamin B-12.

It is thought that B-12 may also play a role in controlling blood levels of homocysteine, the amino acid which is believed to cause damage to blood vessels. Taking supplements of vitamins B-12, B-6 and folic acid has been shown to return the level of homocysteine to normal, and thus it is believed that these B vitamins may provide valuable protection against heart disease.

Additionally, vitamin B-12 is necessary for the function of all nerve fibres, and for the production of genetic material within cells and the metabolism of fats, carbohydrates and proteins. Vitamin B-12 deficiency is more common in the elderly than in younger people.

Foods are your best sources of all nutrients. If your chart shows deficiencies of any B vitamins, increase your intake of vitamin B-rich foods, take a good multivitamin/mineral capsule or a B-complex tablet daily (with a meal) and follow all recommendations to improve your digestion.

Vitamin B-12 is the only vitamin that is found in very few vegetarian sources. It is most plentiful in meat, fish, milk, milk products, and eggs.

Sea vegetables (arame, bladder wrack, dulse, hijiki, kelp, kombu, nori, sea palm and wakame), mushrooms and tempeh (a fermented soy product) contain some vitamin B-12. Although reports vary about their reliability as sources, they are very nutritious foods and it would be a good idea to add them to your diet. We need only very tiny amounts of vitamin B-12 but it is crucial.

Vitamin B-12 is the only vitamin that is stored in the liver and most people have enough stored in the liver to last at least five years. The only people who may not get enough vitamin B-12 in their diets are long-time vegans who haven't eaten any dairy food or eggs for some years. They may need supplements, especially pregnant or nursing women. (Note that many vegans have adequate B-12 blood levels and never need supplements.) Vitamin B-12 works with vitamin B-6 and folic acid. Low levels of B-6 inhibit B-12 absorption. Smoking also inhibits absorption of B-12.

Most people who have a vitamin B-12 deficiency have plenty in their diets, but are unable to absorb it, due to lack of intrinsic factor (a substance necessary for the absorption of B-12). Sufficient stomach acid is also necessary for vitamin B-12 absorption, therefore many older adults are at risk of vitamin B-12 deficiency.

Many of the symptoms of vitamin B-12 deficiency (fatigue, headaches, irritability and light-headedness) resemble those of other nutritional imbalances. A blood test will determine if you have a B-12 deficiency. If your doctor does prescribe a supplement, look for a sublingual (under the tongue) pill or a nasal supplement as they are easier to absorb. B-12 supplements should be taken about one hour before meals for best absorption.