A study published in the Lancet (2007 Jan 20:369(9557)208-16) involved 818 subjects who took either 800 mcg of folic acid per day, or a placebo for three years. The subjects had homocysteine levels that were between 13 and 26 micromoles per liter at the start of the study.
The group receiving the folic acid had an average 26% decrease in homocystine, and a five-fold increase in serum folate levels when compared to the control group. The two groups were tested for memory, sensorimotor speed, complex speed, information processing speed, and word fluency at the beginning and at the end of the study. The group that was supplemented with the folic acid outperformed the control group.
Earlier research that appeared in the Journal of Nutritional Health and Aging. (2004; 8(4):226-32 (ISSN: 1279-7707) looked at vitamin intake and its relation to cognitive function and psychological well-being in over 1000 middle-aged Australian men and women. Specifically dietary intake of folic acid, vitamin B6 and vitamin B12 were beneficial. The subjects filled out questionnaires to determine dietary intake of these nutrients. The researchers concluded: “Vitamin B-12 and B-6 intakes may be positively related to the memory performance of middle-aged men and intakes at around the RDI are associated with better memory functioning for women. The investigation of the dose-response effects of B vitamin supplementation on cognition and mood in middle-aged men and women using objective measures of cognition and accounting for the influence of confounding factors such age and education would be informative.”