Your nervous system is comprised of the central nervous system and the peripheral nervous system. The CNS governs the brain and spinal cord, and the PNS presides over your body, face, arms and legs. Vitamin B-12 plays a vital role in maintaining the myelin sheath, or covering, of the nerves. A diet deficient or insufficient in vitamin B-12 may cause problems with the myelin and the functioning of the nervous system.
Vitamin B-12 is necessary for ridding the body of homocysteine, a substance that is associated with stroke and cardiovascular disease. Vitamin B-12 also plays a crucial role in maintaining the integrity of the myelin sheath that covers the nerve fibers and allows for proper conduction of nerve impulses. A 1992 paper in the journal “Annual Review of Nutrition” reports that the elderly are highly susceptible to vitamin B-12 deficiency caused by their inability to absorb vitamin B-12. Reduced stomach acid, common in older people, leads to reduced absorption of vitamin B-12. Deficiency of vitamin B-12 at any age may lead to disorders of the nervous system.
Nervous System Disorders
A lack of vitamin B-12 may lead to damage of the myelin insulation that protects the nerves. Without this myelin protection, the nerves may cease to function properly leading to nervous system disorders. A deficiency of vitamin B-12 in the diet may cause a degenerative disorder of the spinal cord and nerve damage. This in turn may result in neuropathy, permanent nerve impairment or dementia. A 2007 article in the "American Journal of Clinical Nutrition" followed several studies that found reduced levels of vitamin B-12 may be linked to cognitive impairment and dementia, including Alzheimer's disease. The article stated the results are not conclusive.
Nervous System Symptoms
Deficiencies and even inefficiencies of vitamin B-12 may cause improper functioning of the brain and nervous system. Peripheral neuropathy, injury to the nerves of the peripheral nervous system, may manifest as weakness to your arms and hands, but more often to the legs and feet. There may also be a tingling or numbness and lack of coordination to the limbs. Other neurological symptoms may be disorientation, memory loss, mood changes, psychosis, optic atrophy, impairment in judgment, attention and intellectual abilities as seen in dementia and Alzheimer's disease.
Vitamin B-12 and Folic Acid
Vitamin B-12 and folic acid, part of the vitamin B family, share fundamental roles in the functioning and the prevention of CNS disorders including dementia and mood disorders, according to a 2006 paper in the journal "The Lancet Neurology." Nervous system disorders due to deficiencies in vitamin B-12 are typically seen in men and women between the ages of 40 to 90 years. To maintain healthy levels of vitamin B-12, the recommended dietary allowance is 2.4 mcg per day.