Why We Age by Steven Austad, John Wiley £19

Title: Why we age

Key words: longevity, the ageing process, free radicals, oxidative stress, Alzheimer's, Parkinson's, anti-aging therapies, genes,

Date: April 2001

Category: Directory

Type: Book Review

Author: Steven Austad

Why We Age

by Steven Austad, John Wiley £19.99, ISBN 0471148032

I like the 1928 theory by R. Pearl of a "rate of living", which attempts to correlate a creature's level of energy expenditure with length of life-and thus provides a perfect excuse for inactivity in pursuit of longevity. But the conclusion of Steven Austad's book on ageing is that "your mother (and even more amazingly, the Food and Drug Administration) seem to be right." On average, we will live longer and stay healthier if we take moderate exercise and eat up our fruit and greens.

Austad aims, in the words of his subtitle, to introduce us to "what science is discovering about the body's journey through life". In that he is successful, and this is an interesting and well-documented overview on ageing research: when he comes in the last chapter to the fad remedies, Austad exhibits dry, exasperated humour. There is, unfortunately, no magic potion to announce: no salvation in exercise, dietary restrictions, or vitamin C in large doses.

Jeanne Calment, who died this August aged 122, illustrates the role of inheritance. She was certainly the only verified case of a human living beyond 120 years. Her family was noted for its exceptional longevity-though she attributed her long life to olive oil and port wine.

Science is making considerable progress in understanding the role of the numerous genes that contribute to our fitness and quality of life in old age. Austad introduces us to Michael Rose's work on selective breeding of longer-lived fruit flies and detection of the genes involved. Somewhat surprisingly, he does not consider in much detail the various mutant Caenorhabditis elegans worms, in which genes for longer life have been identified. He repeatedly criticises dependence on laboratory rats and mice, which are bred for early puberty and rapid weight gain-and thus are spectacularly poor subjects for diet restriction experiments in particular.

Oxidative stress is probably the most accepted general mechanism of ageing. Austad thoroughly reviews work on this, and on the particularly notorious "free radical" mechanism of oxidative damage to DNA and other cell components. In my own field of research, oxidative stress has been implicated in many neurodegenerative diseases of old age, such as Alzheimer's and especially Parkinson's-though Austad barely mentions the latter.

Many of the potential anti-ageing therapies which Austad critically discusses are based on antioxidants, vitamins and hormones. He points out that a verdict of "not proven" is appropriate for such measures-and may be overgenerous. There may be significant risks associated with taking the hormone melatonin, or certain vitamins, in abnormally large doses.

The major and most attractive part of the book is Austad's survey of theories of ageing, up to current evolutionary theories. In short, when individuals are isolated from danger and suffer reduced environmental stress, there is less selective pressure on them to breed early and quickly. Austad convincingly demonstrated an effect of this kind in his studies of opossums on an isolated island: they have no predators other than cars, and not only live longer than their mainland cousins but age more slowly.

Austad reminds us that genes whose effects occur after the end of our reproductive lives have no direct selective effect. In populations which breed later in life-almost certainly including New Scientist readers-some of these genes re-acquire direct evolutionary significance, and over many generations we may be selecting against ageing. It seems that the price of late breeding, though, is breast cancer.

This leaves the unsolved mystery of the menopause. Austad quotes Alan Rogers practically demolishing the intellectually appealing "good mother" theory of indirect selection. Does a female human (or pilot or killer whale) pass on more genes when she ceases reproduction and concentrates on the care of her last-born and her grandchildren? She would need to double the number of her grandchildren for this to work.

As we begin to understand the many genes involved in normal ageing, and the mechanisms of oxidation and repair, there is real cause for optimism. This very readable book is a thoughtful contribution to that understanding.