The brain shrinks with age and dementia. In one study, 168 people, aged at least 70, with mild mental impairment, took 800 mcg of folic acid, 500 mcg of vitamin B12, and 20 mg of vitamin B6 per day, or a placebo. After two years, the rate of shrinking had increased 8 percent for placebo and decreased 24 percent for the B vitamin group. Those in the B vitamin group who began the study with higher levels of inflammatory homocysteine saw shrinking slow by 53 percent. Doctors suggest more study to see if B vitamins can maintain brain health.