Common Dietary Supplements for Cognitive Health

MK Gestuvo; WW Hung

Disclosures

Aging Health. 2012;8(1):89-97. 

In This Article

Vitamins B6, B9 & B12

Previous studies have examined the effect of vitamin B supplementation, which included vitamin B6, B9 (folate) and B12 (cyanocobalamin), on cognition. Because elevated homocysteine levels have been associated with an increased risk of dementia and as the most common causes of homocysteine elevation are deficiencies in vitamins B6, B9 or B12,[35] enhanced homocysteine metabolism through vitamin B supplementation may have a beneficial effect on reducing the risk of dementia. Vitamin B6 is an essential cofactor in homocysteine metabolism; vitamin B9 acts as a donor of methyl groups for the methylation of homocysteine to methionine; and vitamin B12 is also required for the methylation of homocysteine to methionine.[36–38] Systematic reviews, which included small trials on the use of B vitamins to prevent or halt the progression of cognitive decline in healthy or cognitively impaired older adults, had not shown any benefit to recommend their use.[36–38] In a recent randomized controlled trial conducted by Ford et al., vitamin B supplementation (400 µg B12, 25 mg B6, 2 mg folic acid) did not result in better cognition over a period of 24 months compared with placebo among cognitively intact older men aged 75 years and older. In the same study, at 8 years follow-up, there was a nonsignificant decrease in the risk of cognitive impairment (OR: 0.72; 95% CI: 0.25–2.09) and dementia (hazard ratio: 0.72; 95% CI: 0.29–1.78).[39] In another randomized controlled trial of cognitively intact older adults with elevated homocysteine levels, supplementation with B vitamins (500 µg B12, 10 mg B6, 1000 µg folate) for 2 years lowered homocysteine levels, but did not demonstrate any improvement in cognitive performance compared with placebo.[40] Another large trial was conducted in older adults with mild-to-moderate dementia (with a mean Mini-Mental State Examination score of 21); 18 months of high-dose B vitamin supplementation with (25 mg vitamin B6, 1 mg vitamin B12, 5 mg folate) showed no benefit on the rate of decline in the AD Assessment Scale-Cognitive subscale score (0.372 points per month for placebo vs 0.401 points per month for vitamin group; 95% CI: of rate difference, -0.06–0.12; p = 0.52).[41] Most studies cited above did not report any significant adverse events with vitamin B supplementation.[36–39] However, the study by Aisen et al. noted an increased incidence of depression in the high-dose supplement group.[41]

Although prior studies did not demonstrate substantial benefit of vitamin B supplementation on cognition, vitamin B is one of the most commonly used supplements.[42]

Adequate intake of B vitamins is essential for health maintenance as they participate in key metabolic processes. However, there is no clear benefit in high-dose vitamin B supplementation for preventing cognitive decline.

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