PureInsight | March 26, 2006
[PureInsight.org] In the cultures of Far East Asia, getting older was considered to be a good thing and used to increase one's social status. In modern times, the Confucian principle of reverence toward the older generations still lingers.
In modern Western society, the general view of aging is closer to that of ancient Greece, where beauty was worshipped and youth was adored.
Whether good or bad, the processes of aging have been considered to be inevitable and a mystery to modern science. Recently, researchers have started to make breakthroughs in this field.
Caloric Intake and Oxidative Stress
There is a Chinese saying that the amount of food one eats in one’s lifetime is predetermined, so one should eat sparsely in order to extend one’s life. It sounds unbelievable but scientific experiments indicate that there is some truth behind it. Scientists have proposed a theory that low caloric intake could slow down aging after observing that caloric-restricted rats live almost 60 percent longer than expected.
It should be noted that “caloric restriction” does not equal starvation. Closely related to the caloric theory is the theory of oxidative stress. Cells use food and oxygen to generate the energy that keeps the body running. This process is most essential for life but it is also a quite hazardous. It is estimated that three percent of oxygen consumption goes to producing free radicals, molecules that are highly reactive and will attack the structures inside the cells. It is estimated that the DNA in each cell will be attacked 100,000 times in a 24-hour period. This is despite the presence of a potent antioxidant system with the sole purpose of neutralising these by-products of metabolism.
Fortunately, there are repair systems, but they are not foolproof. Many people believe that oxidative stress, which leads to a gradual destruction of intracellular structures by free radicals, is one of the major causes of aging.
In one widely publicized experiment that seems to support this theory of oxidative stress, scientist found that genetically altered banana flies with an enhanced antioxidant system live significantly longer than normal banana flies.
Number of Cell Divisions Limited
Molecular biologists have long known that human cells can divide a limited number of times. This phenomenon, known as replicative cell senescence, has been extensively studied in fibroblasts, a type of cells commonly found in connective tissue. Viable fibroblast taken from humans and cultured in vitro start dividing vigorously, but as time passes, the proliferation rate gradually decreases. After approximately 60 rounds of cell division, they stop dividing and cannot be made to divide any further.
The reason behind the replicative cell senescence is mainly thought to be due to the gradual shortening of the telomeres, repetitive DNA sequences at the ends of the chromosomes. Each time a fibroblast divides, the telomeres are shortened. When the telomeres are gone, further division is no longer possible. The telomeres can therefore be thought of as “counting sticks” that limit the number of times a cell can divide.
Whereas a fibroblast may only go through 60 cell divisions, human stem cells (not fully differentiated cells) seem to be able to divide millions of times. These so called stem cells have the ability to produce telomerase, an enzyme that can compensate for the shortening of the telomeres. Stem cells can be found in almost all tissues, for example in the deeper layers of the skin where they constantly divide to produce new skin cells to replace the old ones that are gradually worn out.
However, every time a stem cell divides, some mistakes are bound to be made in the DNA-copying process and these errors accumulate over time as the cell continuously divides. For instance, the skin of a 70-year old is no longer as smooth and beautiful as it was 50 years ago. A stem cell cannot divide indefinitely as it sooner but probably later (after millions of divisions) will have accumulated so many errors in its DNA that it transforms into a tumour cell. Cancers are indeed much more common among the elderly.
The Way Out
Many people pin their hopes on physical training. Whereas exercises indeed can strengthen the body and lessen morbidity, they cannot slow down aging per se. Theoretically, physical exercises make the body age more quickly, since they will make you eat more (increase caloric intake), boost the cellular metabolism (more oxidative stress) and speed up the turnover of cells. However while they might not be able to slow down aging, certain types of physical exercise can most definitely strengthen the body and keep the doctors at a safe distance.
Much contemporary research suggests that mind-body practices can slow down aging. It was known among the ancient Chinese that those who practiced Tai Chi were healthier and lived to be much older than others. Research on yoga has found that the practice significantly decreases oxidative stress. Recently, a study on qigong practitioners found that the turnover of cells had been greatly reduced by the practice.
Mind-body methods are probably the best and most affordable way to stay younger longer.
Resources:
Rubin E, Gorstein F, Rubin R, Schwarting R, Strayer D, editors. Rubin’s Pathology. 4th ed. Philadelphia: Lippincott Williams & Williams; 2005. p. 34-38.
Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P. Molecular Biology of the Cell. 4th ed. New York: Garland Science; 2002. p. 983-1062.
Li QZ, Li P, Garcia GE, Johnson RJ, Feng L. Genomic profiling of neutrophil transcripts in Asian Qigong practitioners: a pilot study in gene regulation by mind-body interaction. J Altern Complement Med. 2005 Feb;11(1):29-39.
Orr WC, Sohal RS. Extension of life-span by overexpression of superoxide dismutase and catalase in Drosophila melanogaster. Science. 1994 Feb 25;263(5150):1128-30.
Yadav RK, Ray RB, Vempati R, Bijlani RL. Effect of a comprehensive yoga-based lifestyle modification program on lipid peroxidation. Indian J Physiol Pharmacol. 2005 Jul-Sep;49(3):358-62.
