Vitamin B12 deficiency linked to neuropsychiatric abnormalities

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KINGSTON, CANADA. Dr. Dianne Delva, MD, Assistant Professor of Family Medicine at Kingston University, reviews the evidence for and against routine supplementation with vitamin B12 (cobalamin) in the elderly. Several studies have shown that anywhere from 5 to 15 per cent of elderly people suffer from a vitamin B12 deficiency. Although the only formally recognized disorder linked to a cobalamin deficiency is megaloblastic anaemia, it is now becoming clear that many neurological and psychiatric symptoms may also be caused by a vitamin B12 deficiency. Ataxia (shaky movements and unsteady gait), muscle weakness, spasticity, incontinence, hypotension, vision problems, dementia, psychoses, and mood disturbances are but a few of the disorders which have recently been linked to possible vitamin B12 deficiencies. Dr. Delva points out that these disorders may occur at vitamin B12 levels just slightly lower than normal and considerably above the levels normally associated with anaemia. She also cautions that the blood level of cobalamin is an unreliable indicator of deficiency and that tissue levels of the vitamin may be quite low even though the blood levels are normal. The best test of cobalamin deficiency involves measuring the blood levels of homocysteine and methylmalonic acid. If the level of these two precursors to the metabolic reactions controlled by cobalamin are high then the vitamin B12 level is low. Vitamin B12 deficiencies may be treated by injections of the vitamin or by oral supplementation. Oral supplementation is just as effective as injections in most people and a lot less expensive. An oral dose of 100-250 micrograms/day is usually adequate although patients with absorption difficulties may need 1000 micrograms/day. Cobalamin has no known toxic effects.

Delva, M. Dianne. Vitamin B12 replacement – To B12 or not to B12? Canadian Family Physician, Vol. 43, May 1997, pp. 917-22