Of all the millions of animals on Earth, only humans get Alzheimer’s disease, which is caused by the formation of metallic "plaques" in the brain, particularly iron ones.

This may be because this dreaded disease somehow facilitated human evolution. But scientists have discovered a new way to stave it off: EXERCISE.

In PhysOrg.com, Alvin Powell quotes neurologist Bruce Yankner as saying, "Something has occurred in evolution that makes our brain susceptible to age-related change." Was that "something" the same thing that makes humans so SMART?

Powell writes, "Studies of other creatures show no sign of similar conditions even in our closest animal relatives. That means susceptibility to Alzheimer’s evolved recently, likely during a period marked by a rapid increase in our brain size. Size alone probably isn’t the determining factor, though, since other animals are known to have even larger brains, including whales, elephants, and even our extinct relative the Neanderthal. Instead, (Yankner says) it is likely that brain complexity and the new large number of cells in the human brain have something to do with it.

"Neurons use more energy than most other cells, (and) with the brain’s increase in complexity over time, its energy demands also rose. Iron plays a key role in a cell’s energy-producing mitochondria, and so iron accumulation leading to genetic damage could be a byproduct of our neuron-rich, energy-gobbling brains."

But a cautiously optimistic new study suggests that, for some people anyway, a daily walk or jog could alter the risk of developing Alzheimer’s or change the course of the disease if it begins. Neurologists obtained the DNA from a group of older volunteers and found that about half of them had the gene that is thought to predispose them to get Alzheimer’s. All of them filled out a questionnaire about their exercise habits.

Previous studies on exercise and Alzheimer’s haven’t shown a correlation between exercise and postponement of the disease, but in the January 24th edition of the New York Times, Gretchen Reynolds quotes psychologist Denise Head as saying that this is probably because this study was the first time that participants were selected for the Alzheimer’s gene. For the group as a whole, exercise provided marginal benefits, but the people with the "bad" gene who reported walking or jogging regularly had plaque accumulation similar to that of volunteers who tested negative for that gene, while those with bad gene variant who rarely or never exercised had the most plaques, putting them at heightened risk for Alzheimer’s in the future.

In her famous diet book "What I Learned From the Fat Years," Anne Strieber (who developed this diet using scientific principles and lost 100 pounds) tells us how to eat, but she also emphasizes exercise, in her chapter titled "The Tyranny of the Body." You don’t have join a gym or be athletic to be fit–she explains that WALKING is the best way to exercise–and it not only exercises the body, it’s good for the brain!

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