"Everything we already know about fighting off chronic disease, like getting sufficient sleep, staying active throughout life, and having a healthy diet" may stave off premature aging of the immune system, too, Epel said.

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Looking at 2, 250 individuals from the Washington Heights-Inwood Columbia Aging Project, researchers found a 40 percent lower risk among those who stuck to this diet, scientists reported in the Annals of Neurology in 2006.

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One of the first solid clues that humans may possess genes that protect against aging came in the 1930s, when researchers at Cornell University showed that rats fed an ultralow-calorie diet lived much longer than normal.

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