Why Do We Age ?

   

  Ponce de León sought the fountain of youth. People today pin their hopes on diets, supplements, exercise, or plastic surgery. It’s a fact: Humans age, and lots of us don’t like how aging makes us look or feel. But what if we were able to slow the aging process?

   Scientists call the process of aging senescence. Why we age, according to Marquette University professor Sandra Hunter, is rather simple: “Cell death… eventually leads to systems malfunctioning and whole body death.” For example, muscle fibers and nerves connected to them gradually die, leading to a loss of strength that begins at age 50 and continues steadily thereafter.

  A deeper question for scientists is, why do the cells die? They’ve come up with several theories, and most likely a combination of them explains the aging process. One theory rests on oxidative damage. Normal cell processes release harmful molecules called oxygen free radicals. Substances in the body called antioxidants neutralize some of them, but a few free radicals escape unscathed and damage cells. Oxidative damage is linked to such diseases and conditions as heart disease, diabetes, and Alzheimer’s.

     Other theories pin cell death on genes, which limit how often the cells can replicate. Parts of our chromosomes, called telomeres, get shorter with each cell division until they are so short the cell can’t divide anymore. Like free radicals, shortened telomeres have been linked to a number of illnesses. Certain genes might also control the life span of an entire organism. Research on worms shows that when scientists mutate genes related to the aging process, they can extend a worm’s life to four times its normal life span. If similar genes exist in humans and can be changed the same way, people could live up to 300 years old.

   For rats, cutting their calorie intake by 30 percent of what’s considered normal lengthens their life span. Scientists predict that similar extreme dieting could have the same effect on humans. And studies in humans have shown that diet and exercise can play a role in lengthening telomeres. “Metaphysically speaking, we age because time passes without our having ied,” says Marquette philosophy professor Susan Foster. “Aging, at least, seems to beat the alternative.”