For those not already familiar with it, in the simplest terms, vitamin B12, one of the eight B vitamins, is the most chemically complex of all the vitamins. This vitamin plays a special role in the nervous system and brain's normal function, and it is integral for the blood's proper formation. Involved normally in the metabolism of all the cells in the body, particularly with DNA synthesis and regulation, it is also important in the synthesis of fatty acids and is involved in energy production. B12 is a vitamin that is soluble in water. Many other vitamins are soluble only in oil, which makes B12 easier for the body to utilize.

Vitamin B12 was originally discovered by those researching how it related to the disease known as pernicious anemia. It is an autoimmune disease that destroys parietal cells in the stomach that secrete a substance known as “intrinsic factor.” The lack of intrinsic factor prevents the normal absorption of B12, causing vitamin B12 deficiency.

In addition to Biermer's disease (pernicious anemia), a deficiency in vitamin B12 can possibly lead to severe and irreversible damage, specifically to the brain and nervous system. At blood levels that are only slightly lower than what is considered normal, a person could experience symptoms like fatigue, depression, and poor memory. Elevation of a compound called homocysteine in the blood and urine can lead to a condition called homocysteinuria. This particular malady might result in additional long-term damage to the arteries and promote clotting which leads to stroke and heart attack. Vitamin B12 deficiency has also been known to cause symptoms of mental disorders like irritability, problems with focus and/or concentration, depression with suicidal tendencies, mania, and psychosis. One major problem for people experiencing these symptoms is that they aren’t specific enough to diagnose a deficiency of the vitamin by themselves.

Vitamin B12 is found naturally in food sources that come from animals like fish, meat (especially liver and shellfish), poultry, eggs, milk, and products made from milk. Lacto-ovo vegetarians can obtain enough B12 by eating dairy products. Unfortunately, vitamin B12 might be deficient in those vegans whose diets are only plant-based foods. They must take care to add supplements to their diets such as multivitamin products or eat B12 fortified foods. Some of the few reliable vegan sources of B12 are in foods that have been fortified with B12, including certain soy products, some breakfast cereals, and fortified energy bars. Brewers’ yeast is also high in B-12.

Vitamin B12 comes as a supplement in lots of processed foods, and can be found in pill form, including added to multi-vitamins. Other forms include liquid, transdermal patches, nasal sprays, or injection and may be purchased alone or in combination with other supplements.

The sublingual form of vitamin B12 is absorbed more directly into the bloodstream by placing it under the tongue, much like heart medicines such as digitalis. In many ways, this form is a more convenient one since no liquids are needed to swallow a pill that may prove to be hard to get down. It is also good for the treatment of B12 deficiency because this version has a higher delivered amount (500 micrograms) for the body’s use, unlike almost any form other than sometimes painful intramuscular injections. The sublingual vitamin b12form also dissolves quickly and generally leaves no unpleasant aftertaste for the user.