ATHENS, Ohio -- A lifelong diet that's low in fat may prevent some health problems that occur with aging, but it doesn't do anything to preserve memory, new research suggests.
Earlier studies of low-calorie diets in mice suggest a physiological benefit to eating healthfully. Mice that ate balanced meals lived longer, had stronger immune systems and showed a greater resistance to cancer. Researchers expected to find a similar preserving effect on the brain.
"We expected to find that a healthy diet would protect memory, because it protects so many other things during aging. But it offered no help," said Linda Bellush, associate professor of psychology at Ohio University and co-author of the study.
Studies of mice revealed diet had no impact on memory loss. Some old mice retained their good memory and others didn't, regardless of their diet.
"We see this in humans as well," Bellush said. "Some older people remain very keen and others don't. We don't know why this happens, but our study suggests diet doesn't play a role."
Researchers compared the cognitive abilities of old mice that had been on a low-calorie diet since 14 weeks of age to those of old and young mice whose diet was not restricted. The mice in the diet-restricted group were fed about 50-60 percent of what the other mice consumed.
The mice were trained to find their way to a hidden platform in a water tank, using landmarks located outside the tank, but within vision of the mice. Researchers found that about 30 to 40 percent of the old mice were unable to find the platform, regardless of their diet.
"We were looking for changes in spatial memory, which is how animals associate objects with their location," Bellush said. "This parallels declarative memory in humans, which is our memory of facts and information that are formed based on relationships among concepts."
Eliminating diet as a cause of memory loss adds some weight to earlier studies in rats that suggested a correlation between changes in the brain and cognitive impairment, Bellush said.
Some theories suggest that calorie restriction causes the brain to release an abundance of certain stress hormones, which can cause damage to cognitive function over time. Another theory, one that Bellush and her colleagues are now exploring, is that certain genes in the temporal lobe of the brain -- where memory is controlled -- either cease gene expression or work too hard, causing memory loss.
"Given the increase in our aging population, many of whom experience cognitive decline, it is very important to understand why this happens," she said.
The study was published in a recent issue of the journal Physiology and Behavior. Other authors were John Kopchick, professor of microbiology; Robert Colvin, associate professor of pharmacology; Aimee Wright, a graduate student in psychology; and Jon Walker, an undergraduate student in biological sciences, all at Ohio University.