Supplement marketers have been aggressively claiming that vitamin B12 and folic acid reduce the risk of memory loss, but a large study on long-term use of supplements found no benefits.
The study involved people with high blood levels of homocysteine, an amino acid. High levels of homocysteine have been linked to memory loss and Alzheimer's disease. Early observational studies claimed there may be some benefit to thinking and memory skills in taking folic acid and vitamin B12, but the results were not duplicated in later randomized, controlled trials.
For the current study in Neurology, 2,919 people with an average age of 74 took either a tablet with 400 μg of folic acid and 500 μg of vitamin B12 or a placebo every day for two years. Tests of memory and thinking skills were performed at the beginning and end of the study. All of the participants had high blood levels of homocysteine.
"While the homocysteine levels decreased by more in the group taking the B vitamins than in the group taking the placebo, unfortunately there was no difference between the two groups in the scores on the thinking and memory tests," said
study author Rosalie Dhonukshe-Rutten, PhD, of Wageningen University in Wageningen, the Netherlands.
"Since homocysteine levels can be lowered with folic acid and vitamin B12 supplements, the hope has been that taking these vitamins could also reduce the risk of memory loss and Alzheimer's disease."
The study was supported by the Netherlands Organization for Health Research and Development, the Dutch Dairy Association, MCO Health, Netherlands Consortium Healthy Aging, Dutch Ministry of Economic Affairs, Agriculture and Innovation, Wageningen University, VU University Medical Center and Erasmus Medical Center, all based in the Netherlands.