Cell death, on a whole-body scale, is what aging is all about. During the aging process, free radicals, highly reactive by-products of our cells' respiration cause damage to the cellular machinery, especially to mitochondria, the tiny power plants that keep a cell functioning.
If malfunctioning mitochondria aren't removed, they begin to discharge suicidal proteins that lead to cell death. Fortunately, younger cells are adept at reducing, recycling and rebuilding.
In this process called autophagy, damaged mitochondria are quickly swallowed up and degraded and the broken down pieces are then recycled and used to build new mitochondria.
As part of the study, to determine how dietary restriction boosted cells' ability to reduce the toxic trash, Christiaan Leeuwenburgh and colleagues examined 22 young and old rats, comparing those allowed to eat freely with those fed a low-calorie, nutritious diet and saw how the amount of certain proteins changed with the rats' age and diet.
The study found that the stress of a low-calorie diet was enough to boost cellular cleaning in the hearts of older rats by 120 percent over levels seen in rats that were allowed to eat what they wanted. The diet had little or no effect on younger rats.
Researchers noted that some proteins responsible for degrading the damaged parts of the cell by autophagy were more abundant in older, calorie-restricted mice.
"Caloric restriction is a way to extend life in animals. If you give them less food, the stress of this healthy habit actually makes them live longer," Leeuwenburgh said.