Don’t take folic acid and vitamin B12 supplements in hopes of preventing age-related mental decline or dementia. Some early research suggested that these B vitamins may reduce the risk by lowering blood levels of homocysteine; people with high levels of this amino acid are at higher risk for cognitive decline as well as cardiovascular disease. But subsequent research has been disappointing, as seen in an analysis of data from 11 clinical trials published in June 2014 in the American Journal of Clinical Nutrition.
Though people taking these vitamins had drops in homocysteine levels, they were just as likely to experience cognitive decline as those taking a placebo. Similarly, other studies have failed to find cardiovascular benefits from these B vitamins.