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010310 Burger and Fries: Brain Food It's Not

March 3, 2001

HealthScout - Remember what you ate yesterday? If not, maybe it's because your diet was full of high-fat foods like fast-food burgers, ice cream and potato chips.

High-fat foods not only clog the arteries, but damage brain function -- at least in laboratory rats, says a new Canadian study.

Researchers compared the cognitive function of rats fed a high-fat diet to that of rats that ate standard, lower-fat laboratory chow. The high-fat diet consisted of 40% fat, similar to what many Americans eat, says study co-author Gordon Winocur, a senior scientist at the Baycrest Centre for Geriatric Care in Toronto and a psychology professor at the University of Toronto.

After three months, the rats on the high-fat diet showed severe impairment on a wide range of learning and memory tasks, the study says.

The same thing might happen to people as well, the researchers say.

"It's entirely possible that people who eat too much fat in their diets over a long period are at risk of reduced brain function," Winocur says.

High-fat diets are known to contribute to cardiovascular disease by clogging arteries and causing a buildup of dangerous plaque and reduced blood flow.

"It stands to reason," Winocur says, "that if blood flow is affected, brain function will be, too."

Fat also can hinder the ability of cells to metabolize glucose, which the brain uses for energy. And glucose deficiency, Winocur says, is known to cause brain impairment.

To test this, the researchers injected the rats on the high-fat diets with glucose. They found that, when given the extra glucose, the rats' cognitive function improved, he says.

"Most interesting was the fact that the glucose worked selectively on one part of the brain, the hippocampus," Winocur says. The hippocampus, near the center of the brain, is critical for memory function.

Rats in the study were divided into three dietary groups: those fed high-fat foods derived from saturated fat (beef tallow); those fed polyunsaturated fat (soybean oil); and those on standard, low-fat lab chow.

Each rat had 21 days of training to learn a simple task: to press a lever to get a food pellet. The trick for the rats was remembering to press the lever every other time researchers placed it in their cage, not every time, to get the food pellet.

After three months, rats on the high-fat diet pressed the lever willy-nilly, the researchers say. The longer the interval between the appearance of the lever in the cage, the worse they performed.

"You could say they were so impaired they were demented," Winocur says. Details of the study appear in the March issue of the journal Neurobiology of Learning and Memory.

Paul Gold, a psychology professor at the University of Illinois, says earlier studies have shown glucose to have dramatic effects on cognitive function in people, including college students and people with Alzheimer's disease.

But experts generally agree it's too soon to recommend glucose as a treatment for memory problems or to enhance memory.

For one thing, doctors don't know yet just how much glucose an individual would need. Too little glucose can impair memory, but so can too much glucose, they say.

"My students ask me if they should load up on glucose before an exam," Gold says, "and I tell them it may help -- but it may hurt."

Winocur adds that high-fat diets, and the resulting glucose deficiency, may affect young children and the elderly more severely than other adults because their brains are more vulnerable.


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