High doses of B vitamins may help to prevent Alzheimer’s disease

Increased intakes of folic acid, vitamin B6 and vitamin B12 seem to prevent shrinkage (atrophy) of key brain regions related to cognitive decline and Alzheimer’s disease in patients with increased dementia risk, reports a new study from UK.

In the randomized controlled trial, blood homocysteine concentration and volume of gray matter brain regions were measured in 156 elderly patients with mild cognitive impairment receiving daily doses of
B vitamins (0.8 mg folic acid, 0.5 mg vitamin B12 plus 20 mg vitamin B6) or placebo for two years (1).
The study results showed that the participants treated with B vitamins had significantly lower plasma homo-cysteine levels (by 29%) and a marked reduction (seven-fold) of gray matter shrinkage when compared to the placebo group. The beneficial effect of B vitamins was confined to participants with high homocysteine levels (above the median of 11 micromoles per liter) at the beginning of the study.

The researchers concluded that high-dose B vitamin supplementation can slow the atrophy (shrinkage caused by cell loss) of specific brain regions, which is a key component in the development of Alzheimer’s disease. Further trials should focus on elderly patients with mild cognitive impairment and high homocysteine levels to see if progression to dementia can be prevented by B vitamin treatment. The results indicate that
B vitamins lower concentrations of homocysteine, which leads directly to a decrease in brain (gray matter) atrophy, thereby slowing cognitive decline, the scientists noted.

Many prospective studies have shown that high levels of plasma total homocysteine are associated with cognitive impairment, Alzheimer’s disease or vascular dementia (2), but randomized controlled trials using
B vitamin supplementation as homocysteine-lowering treatment have shown inconsistent results on cognitive function (3). Factors such as dosage, vitamin combination, duration of treatment and the population treated possibly account for some of the discrepancies (4).

1. Douaud G. al. Preventing Alzheimer’s disease-related gray matter atrophy by B-vitamin treatment. PNAS. Published online May 2013.
2. Wald D. S. et al. Serum homocysteine and dementia: Meta-analysis of eight cohort studies including 8669 participants. Alzheimers Dement. 2011; 7(4):412–417.
3. Wald D. S. et al. Effect of folic acid, with or without other B vitamins, on cognitive decline: Meta-analysis of randomized trials. Am J Med. 2010; 123(6):522–527.
4. Ford A. H. and Almeida O. P. Effect of homocysteine lowering treatment on cognitive function: A systematic review and meta-analysis of randomized controlled trials. J Alzheimers Dis. 2012; 29(1):133–149.