Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, April 19, 1990 TAG: 9004190077
SECTION: NATIONAL/INTERNATIONAL PAGE: A1 EDITION: METRO
SOURCE: NATALIE ANGIER THE NEW YORK TIMES
DATELINE: LENGTH: Long
Here is a diet that extends lifespan by 50 percent or more. It prevents heart disease, diabetes and kidney failure, and it greatly retards all types of cancer.
It eliminates or forestalls many of the usual banes of aging, including cataracts, gray hair and feebleness.
Adherence to the diet keeps the mind supple and the body spry to an almost biblical old age.
On a microscopic level, the diet protects the genes against environmental insults, keeps important enzymes operating at peak efficiency and cuts back on dangerous metabolic byproducts in the body.
And, oh yes, the dieter stays slim. Very, very slim.
These claims are not mere snake-oil phantasms, but the results of astonishing studies that lately have captured broad attention among scientists in the fields of aging, toxicology, oncology and other disciplines.
In laboratory experiments, investigators have discovered that animals raised on a meal plan containing all the necessary vitamins and other nutrients, but only 60 to 65 percent of the calories of the animal's normal diet, will live significantly longer than expected.
By nearly all measures, from the health of the creature's organs and the robustness of its immune system to the lustrous appearance of its fur, the animal on the restricted diet maintains the vigor of youth long after the well-fed control animals in the experiment have become weak, sluggish and grizzled - indeed, long after the controls have died.
Laboratory mice fed the restricted diet, for example, have lived to 55 months.
The average life span of lab mice eating a normal diet, in which they consume as much as they want to, just as most laboratory rodents do, is about 36 months.
"The outcome of caloric restriction is spectacular," said Richard Weindruch, a gerontologist at the National Institute on Aging in Bethesda, Md.
"Gerontologists have tried many things to extend life span, but this is the only one that consistently works in the lab."
Much to their surprise, researchers have found that it does not matter whether the sharply restricted diet is composed largely of fat or of carbohydrates.
As long as the animal receives a minimum amount of protein and enough vitamins and minerals to prevent malnutrition, the creature survives to the same venerable old age.
But researchers warn against people undertaking an ascetic regimen too hastily.
"At this point, I definitely would not recommend a calorie-restricted diet for people," said Dr. Angelo Turturro, a biologist at the National Center for Toxicological Research in Jefferson, Ark., a division of the Food and Drug Administration that is studying caloric reduction.
"There are still too many unknowns about its physiological effects that we have to sort out."
Nevertheless, gerontologists are excited about the insights they will glean by studying caloric restriction.
As a measure of the new enthusiasm surrounding the field, the National Institute on Aging will spend about $3 million this year on studies related to the effects of calorie restriction on longevity, compared with less than $1 million for 1987.
A report on the ability of a low-calorie diet to suppress the growth of breast tumors in lab mice is the lead article in this month's issue of The Proceedings of the National Academy of Sciences, a prominent science journal.
And 400 researchers from around the country and abroad flocked to a recent meeting held in Washington on the physiological consequences of dietary restriction.
"Six years ago you would have had 10 people show up," said Dr. Roy L. Walford, a professor of pathology at the University of California at Los Angeles School of Medicine and one of the pioneers in the field.
Studies are now under way to examine the effects of a low-calorie menu on two species of primates, squirrel monkeys and rhesus monkeys, which scientists hope will be applicable to another sort of primate, human beings.
Most researchers suspect that the monkeys will reap in years what they are losing in calories, and that, by analogy, reduced food intake probably would prolong the life span of humans as well.
"One argument in its favor is that so far dietary restriction has worked in lower animals - worms, insects, protozoans, all across the board," said George S. Roth, a molecular geneticist at the National Institute on Aging who heads one of the primate trials.
But Roth offers an explanation of how caloric restriction might work for lower species but be less effective for animals already endowed with relatively long lives.
By this theory, short-lived species such as insects and rodents could possess a built-in mechanism that allows them to withstand a couple of famine years and still live long enough to reproduce.
But longer-lived species, such as primates, are fertile for so many years that they may not need to have a life-prolonging mechanism set in motion when confronted by a couple of lean years.
To resolve the issue, said Roth, "we really have to wait and see what we get from the monkeys."
Walford said he believes that humans could live to an extraordinarily advanced age if they were to limit their caloric intake.
"Right now, the maximum human life span is about 110 years, and only a few people live to that age," he said. "But if what is true for other species is true for man, then with a sufficiently vigorous caloric restriction, the maximum life span could be extended to about 170."
Walford himself, 65, has been on a low-calorie diet for about five years.
He eats between 1,500 and 2,000 calories a day, compared with an average daily intake for men of about 2,500 calories (for women the figure is about 2,100).
by CNB