Researchers Point to Fruits as Alzheimer's Preventative

WASHINGTON — Some scientists are beginning to think that eating certain fruits and nuts may delay old-age problems like Alzheimer's disease.

Blueberries, apples, blackberries, strawberries, spinach, walnuts and that old retirement community standby, prunes, are seen as promising candidates.

Stephen Ausmus/U.S. Department of Agriculture (enlarge photo) Scientists say fruits with the greatest capacity to absorb potentially health-threatening 'free radicals' in the body include blueberries, blackberries, strawberries, raspberries, plums, avocados, oranges, red grapes and cherries.

Studies on rats and mice show the theory holds promise, according to James Joseph, a U.S. Department of Agriculture researcher. He is a leading proponent of the idea that some foods inhibit inflammation or contain antioxidants that counter the buildup of destructive "free radicals" — highly reactive atoms or molecules that attack disease-causing organisms but also can damage human cells.

But there's no breakthrough discovery, and many researchers remain unconvinced because studies have produced inconclusive or conflicting results.

One study followed more than 1,000 middle-aged Japanese Americans for nearly a decade, recording various lifestyle factors. It found that those who reported drinking three or more glasses of juice per week were significantly less likely to develop Alzheimer's. Other studies have failed to produce the same results.

Epidemiological evidence suggests consumption of tea may forestall the development of problems such as Parkinson's disease and Alzheimer's. But that evidence is also fuzzy, because a lot of other factors may be involved.

The only way to sort out a tangle of conflicting and unconfirmed evidence is through carefully-designed clinical trials, said Laurie M. Ryan, director of clinical trials at the National Institute on Aging. Several trials are under way involving chemicals found in foods.

In the current issue of the journal Current Neurology and Neuroscience Reports, researchers at Columbia University said existing evidence is spotty and often contradictory, and "does not support the recommendation of specific supplements, foods, or diets for the prevention of Alzheimer's disease."

"What I say to guys like that is, 'What else you got? The fact is, you ain't got squat,' " said Joseph, a neuroscientist at the USDA's Human Nutrition Research Center on Aging at Tufts University in Boston, pioneered research on blueberries.

He noted in a telephone interview that blueberries score unusually high in a measurement known as "oxidant radical absorbance capacity," or ORAC, which is basically the degree to which a substance can scavenge free radicals from human cells.

Those radicals are "kind of like your neighbor's old sheep dog," said Joseph. "You're down South and you have on your nice white suit and you go over to visit your neighbor. His dog has been outside, playing in the mud, and when he sees you, he comes and jumps all over you and messes up your suit. He doesn't mean any harm. He's just binding to you."

As people and animals age, their ability to clean up those leftover free radicals starts to slip, Joseph said, and research has shown that persons with Alzheimer's have significantly larger concentrations of them in their brains.

Several years ago, Joseph began feeding blueberries to elderly mice to see what effect they would have on the animals' ability to find their way through a maze.

The animals were bred with a genetic mutation that caused them to produce amyloid beta "plaques," the protein that accumulates in the brains of Alzheimer's disease victims.

When they reached early adulthood at 4 months of age, half of them were given mouse chow that included the human equivalent of a cup of blueberries a day, Joseph said. The other half got mouse chow only.

At 12 months, they got the maze test. The blueberry-fed mice performed as well as healthy mice, and far better than mice with similar levels of brain plaques that got only mouse chow, Joseph said.

The researchers also found that the mice that ate blueberries had increased activity of "kinase," a family of brain enzymes that are involved in the way brain cells communicate with each other, especially in pathways for learning and memory.

A similar experiment with ordinary rats that were not bred for the plaque accumulation showed that blueberry diets were related to remarkable stamina in elderly rats and much better ability to keep their balance while crawling along a rotating rod.

Joseph is skeptical about whether food supplements made up of plant compounds will work. Consuming the substances in food may be critical, he thinks.

He believes Americans, especially the country's 77 million baby boomers, need to include significantly more fresh fruit and nuts in their diets.

"I tell people, 'Eat the walnuts, eat the berries, drink the juice. It can't hurt you, and it might help you a lot,' " he said.

FREE RADICAL FIGHTERS

Oxygen Radical Absorbance Capacity, or ORAC value, of these foods:

Blueberries, 9,019 per cup

Blackberries, 7,701 per cup

Raspberries, 6,058 per cup

Strawberries, 5,938 per cup

Cherries, 4,873 per cup

Plums, 4,118 each

Avocados, 3,334 each

Oranges, 2,540 each

Red Grapes, 2,016 per cup

Source: U.S. Department of Agriculture