Most individuals have enough vitamin B 12 to last several years. When vitamin B12 enters the stomach, it combines with a substance called intrinsic factor. Intrinsic factor assists with the absorption of the vitamin in the small intestine. Absence of intrinsic factor is a common cause of vitamin B12 deficiency.
Deficiency of vitamin B12 occurs when there is either inadequate intake or inadequate absorption. The main sources of vitamin B12 are meat, eggs and dairy products. In addition, several processed foods, such as cereals are fortified with vitamin B12. Vegetarians and the elderly are at increased risk of vitamin B12 deficiency as a result of inadequate intake. There are several risk factors for inadequate absorption. They include:
Inflammation of the stomach (gastritis) or intestines (inflammatory bowel disease)
Previous surgery to remove a substantial part of the stomach or small intestine
The diagnosis of vitamin B12 deficiency can be difficult because the level of vitamin B12 tends to decline gradually over time. In some cases, the level can be quite low before it is detected. As noted before, vitamin B12 is important for red blood cell development and proper functioning of the nervous system. Deficiency of vitamin B12can therefore lead to a type of anemia referred to as megaloblastic anemia. The red blood cells are enlarged and immature because of the lack of vitamin B 12. As a result of the anemia, weakness, tiredness and fatigue may develop. In severe cases, patients may develop congestive heart failure. Neurological symptoms include numbness or tingling of hands or feet, loss of balance, memory loss, visual difficulties and changes in behavior and personality. With prolonged deficiency, irreversible damage of the spinal cord may occur, causing markedly decreased sensation in the feet and loss of balance.
A blood test for vitamin B12 is readily available. When the diagnosis is unclear, additional testing may sometimes be needed. Methylmalonic acid and homocysteine levels are often elevated with vitamin B12 deficiency and are sometimes used to assist with making the diagnosis.
Treatment for vitamin deficiency involves replacing the vitamin orally, by injection, or by inhalation. The oral route is often preferred by many patients, but the injection or inhaled preparations are used if the response to oral supplementation is inadequate.
To prevent vitamin B12 deficiency, vegetarians should have their B12 intake supplemented by either a vitamin supplement or by consuming foods fortified with vitamin B12 (e.g. fortified cereals). The same advice is recommended for individuals over 50. The effects of vitamin B 12 can be very subtle in the early stages, and are sometimes irreversible, so if you have any reason to suspect that you may be deficient, make an appointment with your doctor to have your blood level checked.