To be sure, some of these methods do have what appears to be a rejuvenating influence, not unlike that seen in the use of growth hormone as described in earlier chapters. That is to say there may be the apoearance of a restored youthfulness in certain respects' with definite signs of a reversal in some of the outward manifestations of aging (wrinkles lessened, muscles firming, memory improving etc.) . . but there remains little evidence of any extension of life as a result.

The truth is that only one method of life extension has been proved to be effective, beyond any reasonable doubt, and that is the use of calorie restriction diets within the framework of full intake of all other nutrients. Even antioxidant nutrition, for all its known health benefits (whether through diet or supplementation), has only been shown to extend life in some species (not in all those tested, unlike calorie restriction). Reduction in oxidation activity is, in any case, itself a feature of what happens on calorie restriction diets. Also, a feature of what happens in calorie restriction is the reduction in metabolic rate and the consequent lowering of core temperature, making this a result of the life extension programme, rather than something necessarily needing to be engineered outside of it (although there seems to be no reason why use of methods which achieve this, as outlined in the previous chapter, should not be used to reinforce the dietary methods).

As we hear the siren calls of the various advocates of different life extension methods we need to keep in mind the fact that the one proven method of life extension (calorie restriction) also produces major health benefits, such as a far lesser chance of the diseases associated with old age ever appearing, and the very real chance of those which might already be apparent disappearing.

Do any of the other purported methods of life extension offer these benefits as well? Such health benefits would certainly be easier to prove than the somewhat hard to prove chance of a longer life. The answer is almost always no. Those supposed methods of life extension which I briefly outline below, offer little in the way of proof of prevention of ill-health or of the likelihood of promoting restoration of health once serious disease is present.

Some which do offer health enhancement potentials, such as lowering of excessive serotonin levels (see below) are also related to effects produced on the calorie restriction diet, as one of its many benefits.

So, just what is on offer in the marketplace of ways of increasing the human life span?

Hormones, serotonin inhibitors and the benefits of negative ions

1. Hormone replacement therapy in menopausal women is an example of the way in which a more youthful appearance, and some health benefits, can be created by use of medication. Possible side-effects are apparent in most cases, and none of the hormone replacement methods currently in use make any claim to extend life, merely to ensure that what remains of it has less physical impact.