High-dose folic acid pills — providing as much of the nutrient as 2.5 pounds of strawberries — might help slow the cognitive decline of aging. So says a Dutch study that's the first to show a vitamin could really improve memory.

The research, unveiled Monday at a meeting of Alzheimer's researchers, adds to mounting evidence that a diet higher in folate is important for a variety of health effects. It's already proven to reduce birth defects, and research suggests it helps ward off heart disease and strokes, too.

The new study doesn't show folic acid could prevent Alzheimer's — the people who tested the vitamin didn't have symptoms of that disease.

But as people age, some decline in memory and other brain functions is inevitable. Taking 800 micrograms of folic acid a day slowed that brain drain, reported lead researcher Jane Durga of Wageningen University in the Netherlands.

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

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

That's significant brain protection, with a supplement that's already well-known to be safe, said Johns Hopkins University neuroscientist Marilyn Albert, who chairs the Alzheimer's Association's science advisory council.

"I think I would take folic acid, assuming my doctor said it was OK," Albert said. "We know Alzheimer's disease, the pathology, begins many, many years before the symptoms. We ought to be thinking about the health of our brain the same way we think about the health of our heart."

Indeed, there's enough research now suggesting that there are ways to gird the brain against age-related memory loss and Alzheimer's that the association has begun offering classes to teach people the techniques.

Topping the list:

_Exercise your brain. Using it in unusual ways increases blood flow and helps the brain wire new connections. That's important to build up what's called cognitive reserve, an ability to adapt to or withstand the damage of Alzheimer's a little longer.

In youth, that means good education. Later in life, do puzzles, learn to play chess, take classes.

_Stay socially stimulated. Declining social interaction with age predicts declining cognitive function.

_Exercise your body. Bad memory is linked to heart disease and diabetes because clogged arteries slow blood flow in the brain.

Experts recommend going for the triple-whammy of something mentally, physically and socially stimulating all at once: Coach your child's ball team. Take a dance class. Strategize a round of golf.

Diet's also important. While Alzheimer's researchers have long recommended a heart-healthy diet as good for the brain, Monday's folic acid study is the first to test the advice directly.

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 said it's not clear how folic acid might work to protect the brain. Some studies suggest folate lowers inflammation; others suggest it may play a role in expression of dementia-related genes.

Folate is found in such foods as oranges and strawberries, dark-green leafy vegetables and beans. In the United States, it also is added to cereal and flour products. The recommended daily dose here is 400 micrograms; doctors advise women of childbearing age to take a supplement to ensure they get that much.