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Boosting immunity in the elderly.

Boosting Immunity in the Elderly

In study after study spanning decades, laboratory animals have maintained strong immune systems and lived substantially longer when raised on far fewer calories than they would normally eat. But why this works has been a mystery.

Now a clue as to how lifelong calorie restriction improves immune function in aging mice could point the way to improving older people's ability to fight infection and nip would-be cancers in the bud.

Researchers at ARS' Human Nutrition Research Center on Aging at Tufts found that mice who were raised on about 80 percent of their normal calorie intake synthesized significantly less prostaglandin E2 (PGE2). This hormone-like substance is known to suppress immune function, explains nutritional immunologist Simin Nikbin Meydani. So reducing the hormone helps to boost immune function.

Restricting food intake for extended periods is not practical for lean people. But Meydani says, "It is possible to reduce PGE2 levels through other dietary modifications, such as increasing vitamin E intake."

In fact, Meydani reported success in improving immune function in senior citizens with vitamin E supplements last year before she knew the results of the mouse study. (See Agricultural Research, Feb. 1989, pp. 12-13.)

She expects that a reduction in PGE2 is only part of the answer, but it's a beginning. Now, she says, researchers can design studies to see how individual nutrients known to alter PGE2 synthesis affect the immune system in elderly people.

The eyes of older people could also benefit from follow-up studies. Colleague Allen Taylor, who heads the Nutrition and Vision Research Laboratory at the center, found that calorie restriction significantly delayed cataracts in the test mice--which are from a strain that develops cataracts much as older people do. He says this is the first study that demonstrates the delay of senile-type cataracts in a living animal.
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Author:McBride, Judy
Publication:Agricultural Research
Date:Nov 1, 1991
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