Roughly 5 million Americans suffer from Alzheimer's disease, and those numbers are expected to more than triple by 2050. Certain supplements show promise in elderly patients with dementia, but unfortunately, "where brain-health supplements are concerned, there's no real data to guide what a healthy, middle-aged person should be doing," says Dr. Barry Oken, a professor of neurology and behavioral neuroscience at Oregon Health and Science University in Portland. Still, if you're at high risk for the disease, many experts recommend these supplements.

Omega-3 Fatty Acids
These essential fatty acids appear to have a crucial influence on neurotransmitters in the brain by helping cells better communicate with each other. Although some experts suggest taking DHA (docosahexaenaoic acid), an omega-3 that is a primary structural component of brain tissue, research has focused on fish oil, which contains both DHA and EPA (eicosapentaenoic acid). Vegetarians can try flaxseed oil as a substitute, but experts say the body may not be able to convert flax oil efficiently.
Dosage:  Up to 3,000 mg per day split among three doses.

Folic Acid
In looking at more than 400 elderly patients, University of Iowa researchers found that 75 percent consumed too little folate, a B vitamin that might help prevent heart disease and stroke. In a more recent study published in "The Lancet," supplementing with folic acid (the synthetic form of folate) for three years was shown to improve cognitive function in adults. Even so, experts aren't sure whether taking a supplement can delay or prevent the onset of dementia. If you don't eat a lot of fortified foods such as cereals and store-bought bread, taking a supplement might help. It probably won't hurt, either: Folic acid and other B vitamins are water-soluble, so any excess is flushed from the body.
Dosage: 400 micrograms each day.

Vitamin C and Vitamin E
A 2004 study conducted by the Bloomberg School of Public Health at Johns Hopkins University found that older people who took large daily doses of the antioxidant vitamins C and E were 64 percent to 78 percent less likely to be diagnosed with Alzheimers disease. Although vitamin E lost some of its luster a year later when a report suggested that taking the supplement raised the risk of death, experts say that much of that data focused on synthetic tocopherols and that research techniques were flawed. When choosing a vitamin E supplement, make sure you look for one that contains natural mixed tocopherols, says Dr. David Rakel, director of the Integrative Medicine Program at the University of Wisconsin's School of Medicine and Public Health.
Dosage:  500 to 1,000 mg of vitamin C per day; 400 to 1,000 IU of vitamin E.