Vitamin B complex and dementia - Nutritional Influences on Illness

Townsend Letter for Doctors and Patients,  July, 2002  by Melvyn R. Werbach

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Nutritional deficiencies are common in the elderly. Perhaps 10 to 20 percent of dementias in the elderly are reversible, and malnutrition is an important cause of reversible dementia. In addition to inadequate nutrient intake, other factors -- such as impaired nutrient absorption through the gut lining -- contribute to the deficient nutriture. (1) As an example of nutritionally-caused dementia, we will review the contribution of the vitamin B complex.

Vitamin B12

A deficiency of vitamin B12 is one of the most common nutritional causes of reversible dementia. Although a B12 deficiency is also associated with a megaloblastic (enlarged red blood cell) anemia, the vitamin may be deficient even in the absence of anemia or macrocytosis.

To evaluate the possibility of a vitamin B12 deficiency by lab testing, see if a macrocytic anemia is present and if the neutrophils are hypersegmented. While the serum cobalamin level should be measured, the vitamin may still be deficient even if the serum level is at the low end of the normal range. (2) Inactive cobalamin analogs may be included when serum cobalamin is measured using the popular radioisotope dilution method, so a microbiological assay is preferable. (3)

Other useful lab tests include measurements of serums levels of methylmalonic acid and homocysteine, two metabolites of vitamin B12-dependent pathways which are highly sensitive indicators of deficiency. (4) Finally, serum folate levels should also be measured.

As with all vitamin deficiency syndromes, there is a spectrum of severity ranging from the often isolated findings of marginal deficiency to the full deficiency syndrome. Since the B12 deficiency syndrome includes neurologic deterioration, neurologic findings in a person with dementia should raise the index of suspicion and encourage more complete laboratory testing.

When adequate laboratory testing is unavailable, consider a trial of supplementing vitamin B12 by injection, say 1000 mcg IM twice weekly for several weeks. Even if the injection of vitamin B12 is 'a shot in the dark,' it is both safe and inexpensive.

Folic Acid

A deficiency of folic acid is known to be associated with apathy, disorientation, poor concentration and memory deficits in addition to pyramidal tract damage. Although even the healthy elderly may fail to ingest adequate folate, serum and red cell folate is more likely to be low in patients with dementia. (5) When folate deficiency is the cause of the dementia, the dementia as well as the neurologic symptoms may be at least partly reversible with folate supplementation. (6)

Niacin

Niacin deficiency often presents with dementia unaccompanied by the dermatitis and diarrhea of the classic triad described in pellagra (7); the dementia may be fully reversible within several weeks following the start of supplementation. Moreover, niacin deficiency is not uncommon in the elderly, even despite adequate dietary intake and oral supplementation, (8) and it appears to be fairly common among patients with senile dementia. (9)

Thiamine

Marginal thiamine deficiency is not uncommon in the elderly in general (9) and specifically in patients with Alzheimer's disease. (10) While the memory deficit associated with thiamine deficiency rarely disappears, there is some evidence that adequate supplementation can be of slight benefit in Alzheimer's cases. (11)

Vitamin B6

Perhaps one-third of the elderly population is marginally deficient in vitamin B6. (12) Higher plasma levels appear to be associated with better memory (13) although, compared to the healthy elderly, the intake and nutriture of vitamin B6 does not appear to be lower in Alzheimer patients. (14)

For a group of healthy elderly men, B6 supplementation was followed by modest but significant memory improvement. (15) Whether or not supplementation with the vitamin protects against dementia remains to be determined.

Dementia is a tragic illness, but it is even a greater tragedy for a person to slowly deteriorate in front of family and friends due to a readily treatable B vitamin deficiency.

References

(1.) Evans JR. Alzbeimer's dementia: Some possible mechanisms related to vitamins, trace elements and minerals, suggesting a possible treatment. J Orthomol Med 1(4):249-54, 1987

(2.) Goodman M et al. Are U.S. lower normal 512 limits too low? J Am Geriatr Soc 44(10):1274-5, 1996

(3.) Schilling RF. Vitamin 512: assay and absorption testing. Lob Management 20:317, 1982

(4.) Stabler Spot al. The use of homocysteine and other metabolites in the specific diagnosis of vitamin 5-12 deficiency. J Nutr 126(4 Suppl):1266S-71272S, 1996

(5.) Riggs KM et al. Relations of vitamin B-12, vitamin B-6, foists, and homocysteine to cognitive performance in the Normative Aging Study. Am J Clin Nutr 63:306-14, 1996

(6.) Melamed E et al. Reversible central nervous system dyafunction in folats deficiency. J Neurol Sci 25:93-98, 1975

(7.) Spivak JL, Jackson DL. Pellagra: an analysis of 18 patients end a review of the literature. Johns Hopkins Med J 140(6):295-309, 1977