Resistance to the evidence
Much to the anger of Drs Weindruch and Walford there seems to be a built-in conservatism in medicine which refuses to take seriously the mounting evidence, to which they have added so much, and the contention that it probably relates to humans, largely on the grounds that animal studies do not conclusively prove anything in relation to the human situation. Animal studies, across the spectrum of species, do support the argument for dietary strategies being almost certainly applicable to the human condition and yet such evidence remains inconclusive according to many conservative scientists.

Weindruch and Walford counter this sort of argument by pointing to a wide range of medical methods which are in current general use and for which there is no overwhelmingly 'conclusive' evidence showing that there remains no doubt as to either value or safety. As examples they cite the continuing controversy relating to the relative importance in cardiovascular health of lowering cholesterol levels via diet or drugs. This debate has led to changes in advice for severa1 decades, and still remains unresolved, but it has not prevented authoritative medical guidance on the subject being given to the public time and time again.

Equally equivocal is the new-found medical acceptance that diet is responsible for not less than 40 per cent of all cancers and that prevention via dietary manipulation is a highly desirable objective (increased complex carbohydrate, fresh fruits and vegetable intake and reduced fat, meat and refined carbohydrate intake, a strategy not dissimilar to that needed for lowering cholesterol levels). Since exposure to any carcinogenic factor might precede cancer by as much as 25 years there is no adequate experimental method whereby unequivocal proof of this dietary connection can be made, short of 25 to 30 year long research studies.

This shortfall in certainty has not prevented national and international medical and health organizations from making firm recommendations as to what is and what is not a sound dietary approach to cancer prevention.

Nor, it can be argued, should such a shortfall in absolutely conclusive evidence be the reason for failing to recommend safe nutritional life extension strategies (which incidentally also produce a lowering of cancer incidence and cardiovascular disease in animals). The argument that it is prudent and 'scientific' to wait until we know for sure can be countered by pointing out that sitting on the fence, waiting for evidence which is totally incontrovertible, is far from being a really neutral stance, argue Weindruch and Walford.

Staying with the cancer example, we can see that for authorities to have failed to give publicity to the general consensus of a diet/cancer connection and to not have advocated implementation of an anti-cancer dietary strategy, would in effect have been a policy decision in and of itself.

This is not a case where neutrality means little, for if the evidence pointing to a probable connection (diet/cancer) was subsequently found to be correct, incontrovertibly, the neutral 'hands-off approach could have resulted in an uncountable number of deaths, many of which might have been prevented. Much that we do has to be based on assumptions, made in the light of the evidence available to date, leading us to believe in the probability and likelihood of something being so.

This is where art and logic intervene in the scientific argument, and this is why life extension potentials can be seen to be 'probable' if the animal studies or culture results are taken as guidelines. To state, as has been done by leading members of the study of ageing who are opposed to the making of any recommendations until certainty is apparent, that: 'Dietary restriction will certainly work on rodents (increasing life span) but there is no certainty that it will work in humans' is tantamount to saying that this area of research has to comply with criteria of proof which are not required or necessary in other areas of science and medicine.