The Dutch study is the first to show that a vitamin can really improve memory.

The research, which was released this week, adds to mounting evidence that a diet high in folate is important for a variety of health effects.

Research suggests it helps prevent heart disease and strokes, and it has already been proven to reduce birth defects.

The new study however does not show folic acid prevents Alzheimer's as the people who tested the vitamin had no symptoms of that disease.

As people age, some decline in memory and other brain functions is inevitable, and according to the study's lead researcher, Jane Durga of Wageningen University in the Netherlands, taking 800 micrograms of folic acid a day slowed that brain drain.

In the study, 818 cognitively healthy people ages 50 to 75 swallowed either folic acid or a dummy pill for three years.

When it came to memory tests, Durga says the supplement users had scores comparable to people 5.5 years younger. On tests of cognitive speed, the folic acid helped users perform as well as people 1.9 years younger.

Neuroscientist Marilyn Albert, of Johns Hopkins University, who chairs the Alzheimer's Association's science advisory council, say that is a significant brain protection, achieved with a supplement that is already known to be safe.

Albert says it is known that Alzheimer's disease, begins many years before the symptoms appear and people need to think about the health of their brain in the same way they think about the health of their heart. She says she will take folic acid providing her doctor agrees.

There is now more than enough research suggesting that there are ways to guard the brain against age-related memory loss and Alzheimer's, so much so that the association has begun offering classes to teach people the techniques.

Among these are, exercise the brain to build up cognitive reserve, i.e. learn to play chess, take classes.

Staying socially stimulated, exercising the body, and following a sensible diet.

Alzheimer's researchers have repeatedly recommended a heart-healthy diet as good for the brain.

Previous studies have shown that people with low folate levels in their blood are more at risk for both heart disease and diminished cognitive function.

Durga says, although it is unclear how folic acid works to protect the brain, it has been suggested that folate lowers inflammation or possibly plays a role in expression of dementia-related genes.

Folate is found in foods such as oranges and strawberries, dark-green leafy vegetables and beans.

The recommended daily dose is 400 micrograms and doctors usually advise women of childbearing age to take a supplement.