Doctor K: Could humans live longer lives?

DEAR DOCTOR K: I’ve heard it may one day be possible to slow or stop the aging process. Is there any truth to this?

DEAR READER: In the past, most experts believed that aging was inevitable. Recent research indicates that may not be true.

I remember hearing in medical school the theory that the maximum life span of any species is roughly six times the stretch between birth and maturity. Using this formula, the maximum life span for humans would be 120 years. Indeed, very few human beings have lived longer than 120 years.

On the other hand, life expectancy in developed countries has risen continually for 165 years. At the turn of the 20th century in the United States, just 112 years ago, life expectancy was about 50 years. Today, it is approaching 80 years – a 60 percent increase. Nothing like that has ever happened in human history. How far can it go? We don’t know.

One reason that some people are changing their minds about aging being inevitable is the discovery that some animals don’t seem to age. Many cold-water ocean fish, some amphibians and the American lobster continue to grow bigger, and are able to reproduce and live until something – an accident, a predator or a disease – kills them.

Clearly, though, this is not the case for humans. Why, then, are some scientists wondering if we might be able to overcome the biological cap on aging? Each of us is composed of cells, about 13 trillion of them. When we age, it’s because our cells age. Very recently, we have begun to understand the forces that determine how rapidly cells age – and to control those forces.

Research has shown that restricting calories slows aging. Animals forced to live on 30 percent to 40 percent fewer calories than they would normally consume live 30 percent to 50 percent longer.

We don’t know whether this would be true for humans.