It is in the integrated concepts of cellular and organ-related changes that a truly manageable understanding of the ageing process becomes possible. John Mann, writing in his book Secrets of Life Extension (Harbor, San Francisco, 1980) describes some of the 'integrated theory' thinking of a number of researchers. He discusses the work of Howard Curtis of Brookhaven National Laboratory who held that there was a 'composite theory of ageing', in which factors such as radiation, mutation and toxic accumulation all worked together to hasten the speed of degeneration.
He also says that:
In their 'integrated theory of ageing', Carpenter and Loynd explain how interactions of stress, metabolic waste production, free radical build-up, and somatic mutations work together to accelerate the rate of cross-linkage and other molecular changes that immobilize many of the body's active molecules.
He continues by describing Hans Kugler's 'combination theory of ageing, in which several contenders appear together as causes of this process. These stress factors are seen to be problems which could at one time have been adequately dealt with by the body, but which, in combination, become overwhelming and thus accelerate the ageing process.
So, whether we are looking at integrated, composite or combination theories we seem to be seeing the same thoughts emerging; that a number of the cellular-change patterns lead on to organ dysfunction and a collapse of the body's ability to deal with the continuing onslaught.
Newsweek magazine journalists Sharon Begley and Mary Hager ('Fountain of Youth', 5 March 1990) summarize the varying theories thus:
The first [theory] holds that the changes that accompany aging
are the inevitable result of life itself. DNA, the molecule of
heredity, occasionally makes mistakes as it goes about its
business of synthesizing proteins; metabolism produces toxic
avengers (free radicals) that turn lipids in our cells rancid and
protein rusty. This damage accumulates until the organism
falls apart like an old jalopy . . .
The other theory argues that aging is genetic; programmed
into the organism like puberty. There is evidence for both sides.
In fact, since we know that all sorts of outside factors influence life expectancy, it has become increasingly clear that both theories are correct and that it is on the underlying, genetically predetermined, maximum life expectancy (say 120 years in humans) that the multiple forces of toxicity, energy, infection, nutritional deficiencies or excellence, stress factors etc. are acting, and that it is to these areas that we need to address our attention in order that the potential life span might be approached, in a good state of health. I will show in great detail that it is possible to beneficially influence life expectancy in animals and humans by means of dietary manipulation, and the effects of this are to first improve health and only second to allow a longer life to emerge, not the other way around as so many research scientists seem to imagine.
This is because, unlike the rusting jalopy of the Newsweek analogy, we have something which no automobile has - a self-adjusting, self-repairing, self-healing potential called homoeostasis working for us - and it is dietary manipulation which can trigger its efficiency when it is doing its job in an unsatisfactory way.
In the next chapter I describe the complex, hard-working and often dangerous life of a typical cell, indicating some of the amazing qualities and properties it possesses as it performs its multitude of tasks in the face of a remarkable array of hazards. It is important to understand the effect of these hazards (e.g. free radical activity) and to realize that the changes which result from them are the commonest age-associated features which can be identified at the cellular level. These changes are dominated by the gradual accumulation in cells of what are called 'altered proteins' which result in all or some of the following states: