Not only does vitamin B12 help in the formation of healthy red blood cells (which protect against anemia), it is also involved in the maintenance of the myelin sheath, the fatty substance that covers nerves and enables them to function properly. The body also needs this vitamin for cell replication, proper energy metabolism, and to create the genetic material in cells known as DNA and RNA.
Vitamin B12 is also of potential value in treating the effects of aging and Alzheimer's disease, as well as depression, the skin disorder known as rosacea, tinnitus (ringing in the ears), and various neurologic problems. It may also help to prevent heart disease and boost the immune system.
Vitamin B12 is the only B vitamin that the body stores in substantial amounts. In addition, most people get adequate amounts from their diets. For the body to absorb the vitamin, however, it has to be separated from the protein in food, a complicated process. An individual must be able to produce enough digestive enzymes, stomach acid, and intrinsic factor (a substance secreted by cells in the stomach lining) for this separation to take place. Then the vitamin bonds with intrinsic factor and is transported to the small intestine, where it is absorbed. Some individuals are unable to make sufficient quantities of intrinsic factor or stomach acid as they age, a situation ripe for a deficiency to develop. Experts estimate that as many as 20% of older adults are deficient in vitamin B12 but don’t know it.
In addition other groups are also at particular risk for a deficiency: those with ulcers, Crohn's disease or other gastrointestinal disorders, and those taking medication for epilepsy, chronic heartburn, or gout. In addition, heavy drinkers are likely to have low levels of B12 because excessive alcohol consumption hinders the nutrient's absorption. People who don't eat any meat products (vegans) are also at risk. A deficiency can cause fatigue, depression, confusion, memory loss, muscle weakness, and numbness and tingling in the hands and feet due to nerve damage.
