Elderly mice on a very low-calorie diet for as little as four weeks
reversed many of the changes in the activity of various genes that had occurred during normal aging,
according to a new study published in the Proceedings of the National Academy of Sciences (September 11,
2001 98:10630-10635)The research study uses a new technology to pinpoint which genes are active in mice at different ages, may help scientists to understand how calorie restriction extends animals' lifespan and, eventually, to develop longevity therapies for humans. Calorie restriction and longevity research in the past 60 years have consistently shown it to the only treatment that extend mammals' lifespan, although its effectiveness in people is unproven is currently under study as well. There is no reason to expect that the result would be different in humans.
In various animal studies, calorie restriction has been shown to lower the incidence of cancer and delays the onset of other age-related diseases.
Many theories have been advanced on the exact mechanism on how calorie restriction works, and recently, researchers are able to examine how calorie restriction diets affect the function of many of the approximately 30,000 genes present in a mouse or a person.
In this study, some mice were fed a low-calorie diet -- providing just enough food to prevent starvation -- from the time they were weaned, and others were switched from a normal to a low-calorie diet for four weeks starting when they were 34 months old. The researchers found 20 genes whose expression increased with age. Also found were several genes associated with inflammation, a process that in the liver can contribute to the development of cirrhosis or cancer. Others genes were discovered to be involved in protecting and repairing cells and in preventing cell suicide. In 14 of the 20 genes, long-term calorie restriction completely or partially prevented the age-related changes.
The expression of 26 genes decreased with age. Some were responsible for putting the brakes on cell growth and division, and an age-related reduction in their activity could explain why mice of the strain studied often die of cancer. Others affected genes were responsible for detoxifying foreign substances such as drugs. Researchers found that prolong calorie restriction reversed the age-related changes in 13 of the 26 affected genes by 70 percent. This is highly significant because it shows that it is never too late to start calorie restriction, even among the elderly.
Calorie restriction is not the same as starvation. In a
properly conducted calorie restriction program, cells are maintained at optimum nutrition through eating
the right kinds of food without sacrificing nutrition. Starvation does not lead to longevity, and this
confusion must be dispelled.