Fountain of
Youth

The primal search for the Elixir of Youth has never ceased. Just as Ponce deLeon's fountain of eternal youth proved an illusion, so too have all the many nostrums advertised over the years to ward off old age. Longevity is at least in part hereditary, and the affirmation by an American jazz musician, that he had achieved extreme old age thanks to never eating anything that wasn't fried, should be treated with reserve. Nor can one be too sure about the 150-year-old yoghurt eaters of Asia Minor

Perhaps the most rational of all the measures that have been tried to prolong life is based on the theory that the agents of decrepitude are free radicals, formed as by-products of some metabolic reactions. These are highly active molecules and can be destroyed by "scavengers," prominent among which are vitamin E and the carotenes, related to vitamin A. But, while these may certainly do some good, it has never been established that they really do retard the ageing process, and as we have seen, taken in the huge quantities that are not now uncommon in the developed world (and especially in the United States), they probably do harm rather than good. The only experimental means yet discovered of prolonging life in laboratory animals is calorie restriction. This strikingly increases the life-span and reduces the symptoms of ageing in rodents, but a corresponding reduction in human calorie intake would mean a drop from an average 2500 to 1750 calories per day. Such a dismal regime would certainly make one's existence seem longer, but the criticism that what applies to rodents need not apply to man was countered by similar experiments on primates, which bore out the effect.

One direction that the inquiry into the mechanism of ageing has taken is a search for the changes in levels of various metabolic intermediates in relation to calorie intake. All theories of ageing now embody the premise that evolution can act only in the interests of procreation, since (by definition) natural selection operates by favouring traits (genes) that promote the propagation of the species. Therefore increased survival beyond the age of reproductive activity is of no evolutionary benefit. When food is plentiful an animal can both grow and reproduce, while when it is scarce it does best to suppress both processes and switch to a mode in which the body's resources are husbanded and its reproductive capacity protected for the future. If the metabolism is boosted in times of plenty there should be more rapid utilization of the blood sugar (glucose) for the production of the body's energy source, ATP. It is the reactions by which ATP is formed in the cell's power-houses, the mitochondria, that generate free radicals.

In any event, a group of researchers at the National Institutes of Health near Washington discovered that the sequence of reactions could be interrupted by a chemical analogue of glucose, which would jam the enzymic machinery. This analogue is a simple substance, 2-deoxy-D-glucose, or 2DG. When given to rats, the 2DG reduced the level of blood glucose and the amount of circulating insulin, the hormone that, as we have seen, allows the blood glucose to do its work. The metabolism slowed and the body temperature fell somewhat. The animals did not eat less, but they became leaner and apparently fitter. These results have stirred up a good deal of interest (especially, one might hazard, among older scientists), but 2DG is not yet the Elixir of Youth because, for one thing, it is toxic at only slightly elevated concentrations or when administered for an extended period. But the results do suggest that a substance may eventually be found that will simulate the effects of eternal fasting without biting back in some other way. The social consequences of course could be too alarming to contemplate.

Meanwhile, your best chance on current, and highly incomplete, evidence of dying old lies in not growing fat (for obesity, as we have seen, hugely increases the likelihood of terminal and lesser ailments); eating generous amounts of fruit and vegetables --- tomatoes, which contain free radical scavengers are especially recommended; keeping dairy foods down to reasonable limits; eating fish regularly; drinking alcohol (though, sadly, only in moderation); drinking coffee, at least if your blood pressure is not too high (for this seems to diminish the incidence of bowel cancer); and possibly taking one multivitamin pill (containing folic acid) every day. And then there is the Second-World-War mantra, now seldom heard, that "a little of what you fancy does you good."

--- From The Terrors of the Table
The Curious History of Nutrition
Walter Gratzer
©2005 Oxford University Press