A multicenter, randomized, double-blind controlled trial included a total of 409 subjects. The trial evaluated high-dose folate, vitamin B6, and vitamin B12 supplementation in individuals with mild to moderate Alzheimer’s disease (AD). The patients received either 5 mg folate, 25 mg vitamin B6 and 1 mg vitamin B12 or placebo daily for 18 months. The outcome was a change in the AD Assessment Scale (ADAS-cog). Vitamin supplement was effective in reducing homocysteine levels (mean [SD], –2.42 [3.35] in the treatment group vs. –0.86 [2.59] in placebo group), but it had no beneficial effect on the rate of change in ADAS-cog score during 18 months (0.372 points per month for placebo group vs. 0.401 points per month for the treatment group, 95% CI –0.06 to 0.12), or on any secondary measures.