HOW TO LIVE TO BE 100
Since aging and lifespan are broadly determined by the genetic plan of a
species, attention has been directed to the possibilities of their modification by
altering the environment. The biologist Jacques Loeb showed early in the 20th
century that the life span of the fruit fly was halved by every 10-degree rise in
temperature. This led to impractical speculations about prolonging the human life
span by experimenting with various degrees of cooling the body. Fairly severe
restriction of caloric intake in the laboratory rat can more than double its life span,
chiefly by prolonging the period of immaturity. Caloric restriction is so far the only
factor shown to have a major effect on aging and lifespan. Unfortunately, food
restriction has less effect on species other than rodents. It has not been shown that
undernourished human populations live longer, but vitamin deficiency, disease, and
poor medical care found in such groups complicate the analysis. In geriatric
medicine, the hope is to eliminate the disease processes that prevent human beings
from living to the end of their natural lifespan.
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