Vitamin B12, a water-soluble vitamin, plays an important role in neurological function, as well as in red blood cell formation, DNA synthesis and fat and protein metabolism. Inadequate intake or absorption of this nutrient can cause vitamin B12 deficiency, a condition that, when left untreated, can cause permanent neurological damage. Once diagnosed, vitamin B12 deficiency can be treated with B12 injections or high oral doses of the vitamin.
Neurological Damage
Prolonged, untreated vitamin B12 deficiency can cause permanent neurological damage, leading to dementia, paranoia, psychosis and hallucinations. B12 deficiency may exacerbate dementia associated with Parkinson's disease or Alzheimer's disease, notes the Centers for Disease Control and Prevention. The specific causes of B12 deficiency's effects on nervous system and neurological functions remain unknown. The CDC recommends that doctors test the B12 status of all patients with unexplained cognitive decline.
Symptoms
Vitamin B12 deficiency often causes megaloblastic anemia, with symptoms such as weakness, fatigue, shortness of breath, difficulty concentrating, reduced appetite, constipation and weight loss. Symptoms of nervous system damage caused by B12 deficiency may include peripheral neuropathy, or numbness and tingling in the hands and feet, as well as sensory loss and difficulty maintaining balance. Symptoms of neurological damage caused by B12 deficiency may include confusion, memory problems, depression, vision loss and cognitive and behavioral changes.
Neurological Damage Without Anemia
Large amounts of folic acid can correct the megaloblastic anemia commonly associated with vitamin B12 deficiency, making the condition harder to detect. High levels of folic acid do not correct the neurological damage associated with B12 deficiency, however, and, in some cases, high levels may worsen cognitive symptoms, notes the National Institutes of Health Office of Dietary Supplements. For this reason, adults should limit their daily intake of folic acid from supplements and fortified foods to 1,000 mcg.
Neurological Damage in Infants
Low vitamin B12 in pregnant women increases the risk for neural tube birth defects in babies. Infants exclusively breastfed by vegetarian or vegan mothers have a higher risk for serious effects associated with vitamin B12 deficiency, including failure to thrive, hypotonia, ataxia, developmental delays, anemia and general weakness. Irreversible neurological damage can occur if the deficiency is not diagnosed and treated.
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