The Effects Of A Vitamin B12 Deficiency

Vitamin B12 and folate each activate the other and have interdependent activities, according to Eleanor Whitney and Sharon Rolfes in "Understanding Nutrition." Vitamin B12 removes a methyl group to activate folate, and when folate gives up its methyl group, the vitamin B12 coenzyme becomes activated. Vitamin B12 maintains the protective sheath that protects nerve fibers and promotes normal nerve growth. It also contributes to bone cell activity and metabolism. Vitamin B12 attached to proteins in food is released by the action of hydrochloric acid and the pepsin enzyme in the stomach. Then vitamin B12 binds with an intrinsic factor and passes to the small intestine where it is absorbed into the bloodstream and transported by binding proteins. Because vitamin B12 is recirculated in the body, even with minimal intake, healthy people rarely develop a deficiency. Most vitamin B12 deficiencies reflect inadequate absorption rather than inadequate intake.

Effects on Blood

A vitamin B12 deficiency may result from atrophic gastritis, especially in people over 60 years of age. As a result, the damaged stomach cells are unable to produce sufficient hydrochloric acid and intrinsic factor. Without these components, even with adequate vitamin B12 intake, a deficiency of vitamin B12--known as pernicious anemia or megaloblastic anemia--develops. If folate becomes trapped in the inactive state because of a vitamin B12 deficiency--or is unavailable because of a folate deficiency--DNA synthesis slows down. Rapidly dividing blood cells are the first to be affected by folate deficiency anemia. This condition is marked by large, immature red blood cells with an inability to divide. Either vitamin B12 or folate will clear up this type of anemia. Unfortunately, folate can mask a vitamin B12 deficiency. If folate is provided when vitamin B12 is needed, the result can be devastating neurological symptoms, according to "Understanding Nutrition." Folate masks a vitamin B12 deficiency by eliminating the blood symptoms while allowing nerve damage to progress undetected.

Effects on Nerves

Neurologic results of vitamin B12 deficiency include peripheral neuropathy and damage to the myelin sheath surrounding and protecting nerves. Paralysis begins at the extremities and creeps its way inward and up the spine, according to "Understanding Nutrition." Early detection and correction can prevent permanent nerve damage and paralysis. Other symptoms of vitamin B12 deficiency, according to the Office of Dietary Supplements, include difficulty maintaining balance and soreness of the mouth or tongue.

Psychiatric Effects

Vitamin B12 deficiency can manifest in irritability and personality change, according to the American Academy of Family Physicians. Other psychiatric effects include a mild memory impairment or dementia, depression, confusion and rarely psychosis.

Cardiovascular Effects

A deficiency of vitamin B12 may be associated with increased risk of myocardial infarction and stroke, according to the American Academy of Family Physicians. As with folic acid deficiency, vitamin B12 deficiency results in an excess level of homocysteine, which is a risk factor for atherosclerosis and coronary artery disease.

Effects on Infants

Infants suffering from a deficiency of vitamin B12 experience failure to thrive, various movement disorders, developmental delays and megaloblastic anemia, according to the Office of Dietary Supplements