On a slightly different track, Dr. Mattson finds that restricting calories may help immunize brain cells against damage and disease in a different manner. He and colleagues have detected specific molecular changes in the brain cells of animals eating lower calorie diets. Remarkably, he finds that overeating weakens or primes brain cells for damage and conversely that restricting calories bucks up nerve cells, making them stronger and more resistant to damage. Underfed animals are much less apt to develop the signs of neuronal damage characteristic of degenerative brain diseases, such as Alzheimer’s, Parkinson’s, and Hunting-ton’s diseases.
In recent tests, Dr. Mattson cut the calorie intake of young rats (age two months—comparable to five years in humans) by 30 percent compared with rats allowed to eat as much as they wanted. All the rats were then subjected to brain toxins that mimic the destruction of neurons in the hippocampus, as inflicted by Alzheimer’s, and destruction of nerve cells in the striatum, a brain region affected in Parkinson’s. Afterward, the animals were taught to perform feats of memory, learning, and motor coordination. Unquestionably, the calorie-restricted animals performed much better on the tests of mental and motor functioning. “The beneficial effects of the dietary restriction were striking,” said Dr. Mattson.
For example, rats free to eat anything showed severe memory deficits, but calorie-restricted rats exhibited little or no memory loss, despite the toxic assaults on their brains. In tests of balance and motor skills, calorie-restricted rats lasted three minutes before falling off a slowly rotating rod. Well-fed rats toppled off within a minute. But the proof of protection was seen when the animals’ brain cells were meticulously examined postmortem. After three months, the well-fed rats had only half as many brain cells left as the calorie-restricted animals! The lower calorie intake had somehow shielded their brains from massive destruction.
The implications, of course, are that human brains could benefit as well. Indeed, new evidence suggests it’s true. About ten years ago, Richard Mayeux, M.D., at Columbia University College of Surgeons and Physicians, started tracking 1500 healthy people to determine the impact of their diet on developing degenerative brain diseases. He has discovered that calorie intake does make a big difference. “After considering body size, people who took in fewer calories had a substantial reduction in the risk of Alzheimer’s disease,” he says. Moreover, the most “protected” brains belonged to the lower-calorie group who also ate a low-fat, high protein, high carbohydrate diet. Fewer calories also cut the risk of Parkinson’s, he says.
Dr. Mattson says the “mild starvation” of fewer calories put stress on the brain cells causing them to grow stronger. “It’s much like, the more you use your muscles, the stronger they become, and resistant to injury. It’s also true for neurons,” he says. Mattson theorizes that when stressed, the nerve cells “switch on” certain genes that increases levels of growth factor in the brain, making the cells more resistant to damage from free radicals, involved in brain degeneration.
It took a month or two of calorie restriction in rats before brain protection kicked in, says Dr. Mattson. That would be several years in humans. To meet the same calorie restrictions as the animals, typical Americans would have to shave off seven hundred to a thousand daily calories, bringing consumption down from an average 2500 to 3000 daily calories to 1800 to 2000 calories per day. Mattson, who is five feet nine inches and weighs 125 pounds, says he eats about 2000 to 2200 calories a day.
Cutting drastically down on calories is a hard sell to Americans, Dr. Mattson agrees. But he believes it’s worth it considering the high stakes—your brain. He and other scientists are also looking for shortcuts, such as drugs or other less severe measures, that may do much the same thing as calorie restriction without the hardship. Still, even if you don’t make severe reductions, curtailment to any degree may help ward off eventual mental decline. Every calorie not eaten and not burned means fewer free radicals to attack your brain cells.
BOTTOM LINE: Burning more calories weakens brain cells and accelerates the aging of the brain.