A prescription that may extend life

By Michael Mason / The New York Times

Published: October 30, 2006

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"The demographic wave entering their 60s is enormous, and that is likely to greatly increase the prevalence of diseases like diabetes and heart disease," said Dr. S. Jay Olshansky, an epidemiologist at the University of Illinois at Chicago, and one of the paper's authors. "The simplest way to positively affect them all is to slow down aging."

Science, of course, is still a long way from doing anything of the sort. Aging is a complicated phenomenon, the intersection of an array of biological processes set in motion by genetics, lifestyle, even evolution itself.

Still, in laboratories around the world, scientists are becoming adept at breeding animal Methuselahs, extraordinarily long lived and healthy worms, fish, mice and flies.

In 1935, Dr. Clive McCay, a nutritionist at Cornell University, discovered that mice that were fed 30 percent fewer calories lived about 40 percent longer than their free-grazing laboratory mates. The dieting mice were also more physically active and far less prone to the diseases of advanced age.

McCay's experiment has been successfully duplicated in a variety of species. In almost every instance, the subjects on low-calorie diets have proven to be not just longer lived, but also more resistant to age-related ailments.

"In mice, calorie restriction doesn't just extend life span," said Leonard P. Guarente, professor of biology at the Massachusetts Institute of Technology. "It mitigates many diseases of aging: cancer, cardiovascular disease, neurodegenerative disease. The gain is just enormous."

For years, scientists financed by the National Institute on Aging have closely monitored rhesus monkeys on restricted and normal-calorie diets. At the University of Wisconsin, where 50 animals survive from the original group of 76, the differences are just now becoming apparent in the older animals.

Those on normal diets, like Matthias, are beginning to show signs of advancing age similar to those seen in humans. Three of them, for instance, have developed diabetes, and a fourth has died of the disease. Five have died of cancer.

But Rudy and his colleagues on low-calorie meal plans are faring better. None have diabetes, and only three have died of cancer. It is too early to know if they will outlive their lab mates, but the dieters here and at the other labs also have lower blood pressure and lower blood levels of certain dangerous fats, glucose and insulin.

"The preliminary indicators are that we're looking at a robust life extension in the restricted animals," Weindruch said.

Despite widespread scientific enthusiasm, the evidence that calorie restriction works in humans is indirect at best. The practice was popularized in diet books by Dr. Roy Walford, a legendary pathologist at the University of California, Los Angeles, who spent much of the last 30 years of his life following a calorie-restricted regimen. He died of Lou Gehrig's disease in 2004 at 79.

Largely as a result of his advocacy, several thousand people are now on calorie-restricted diets in the United States, says Brian M. Delaney, president of the Calorie Restriction Society.

Mike Linksvayer, a 36-year-old chief technology officer at a San Francisco nonprofit group, embarked on just such a diet six years ago. On an average day, he eats an apple or some cereal for breakfast, followed by a small vegan dish at lunch. Dinner is whatever his wife has cooked, excluding bread, rice, sugar and whatever else Linksvayer deems unhealthy (this often includes the entr?e). On weekends, he occasionally fasts.

Linksvayer, 6 feet tall and 135 pounds, estimated that he gets by on about 2,000 to 2,100 calories a day, a low number for men of his age and activity level, and his blood pressure is a remarkably low 112 over 63. He said he has never been in better health.

"I don't really get sick," he said. "Mostly I do the diet to be healthier, but if it helps me live longer, hey, I'll take that, too."

Researchers at Washington University in St. Louis have been tracking the health of small groups of calorie-restricted dieters. Earlier this year, they reported that the dieters had better-functioning hearts and fewer signs of inflammation, which is a precursor to clogged arteries, than similar subjects on regular diets.

In previous studies, people in calorie-restricted groups were shown to have lower levels of LDL, the so-called bad cholesterol, and triglycerides. They also showed higher levels of HDL, the so-called good cholesterol, virtually no arterial blockage and, like Linksvayer, remarkably low blood pressure.