You raise an important issue about which we have more questions than answers. I can tell you that studies of twins have shown that genes influence only about 25 percent of the variation in human longevity. Beyond that, we have to look at many other factors including “gerontogens” – substances that can accelerate aging. These include the mix of some 4,000 toxic chemicals in tobacco smoke, arsenic in groundwater, benzene in industrial emissions, ultraviolet radiation from the sun, as well as the health effects of obesity, nutrition, and psychological stress.

One approach to the study of aging is to focus on the brain by measuring levels of the beta-amyloid protein linked to Alzheimer’s disease, but that would tell us only some of what’s going on in the brain, and nothing about what’s happening elsewhere in the body.

Another clue could come from the length of telomeres, repeating DNA sequences at the ends of chromosomes. Intact telomeres prevent chromosomes from fusing with one another or rearranging – undesirable changes that can lead to cancer and other life-threatening diseases. Research has shown that as cells replicate and age, telomeres get shorter and shorter and that when they finally disappear, cells can no longer replicate. Some experts suggest that the length of telomeres may be a marker for biological aging. The shorter your telomeres, the “older” you are, regardless of your chronological age.

In one study involving the effect of green tea on aging, investigators reported that the average difference in telomere length corresponded to “approximately a difference of five years of life,” which suggests that people who drink green tea regularly may be younger biologically than those who don’t. The researchers suggested that the “antioxidative properties of tea and its constituent nutrients may protect telomeres from oxidative damage in the normal aging process.”

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