Aging, like the weather, is a subject everyone talks about but no one seems able to do much about. Theories and nostrums abound, from wrinkle creams to hormone supplements, many with compelling evidence in their favor, but none has earned the consensus of the scientific community, save one. There is substantial and accepted evidence that caloric restriction (CR) can increase lifespan by at least 30% in every animal tested. So far these experiments have indicated that the maximum effect is reached at a 33% reduction in daily calories, but a more modest 10% is presumed to have at least some beneficial effect. They also suggest that a longer interval between meals is an important factor, independent of total calories consumed. The principal drawback to these studies is that they are by-and-large limited to subjects with short life spans, like mice, rats, flat worms, insects and a variety of one-celled organisms. The few human subjects that have produced reliable data, such as those in Biosphere 2, seem to have fared well despite substantial weight loss, but they have yet to reach even their actuarial lifespan. (1)
This information certainly gives one pause to reflect on where a nation that is 60% overweight is headed, in spite of our miraculous advances in medicine and health care. One might say that the popular vote favors death and disease over hunger. Isn't there an easier way?
Although explanations abound, the stress consequent upon reduced caloric intake takes center stage as a fundamental factor. A variety of adaptive scenarios has been proposed.
* Stress induces cells to slow their growth rate, and the lifespan of cells appear to be limited to a finite number of cell divisions.
* As growth slows, so does metabolism, reducing the population of reactive oxygen species (ROS) that cause oxidative damage, a principal mechanism of disease activation.
* CR lowers blood glucose and consequently levels of insulin and the variety of associated hormones. Recollecting the numerous destructive effects of diabetes brings the advantages of this metabolic alteration into sharp perspective.
* A coincident mechanism lowers body fat, reducing the detrimental excess of adipose-generated hormones.
* At the same time, the stress of CR promotes protective hormones and stimulates the immune system.
The favored explanation currently circulating is that reduced mitochondrial damage accompanies the lowered metabolic rate. Mitochondria are poorly protected from oxidative damage by free radicals (ROS) and have but a single enzyme to effect repairs in mitochondrial DNA. As the cells' sole energy source diminishes, so do all their other functions. The result is aging.
An extension of these theories and findings has been explored by David Sinclair at Harvard Medical School. (2) He notes that the many beneficial chemical nutrients derived from plant products and...