How long will you live for? Most people, irrespective of their actual lifetimes, would probably agree that they would not live quite long enough. This desire for a long life is driven partly by our universal fear of dying, and partly by our insatiable desire to see what happens next. Thus, as soon as we address the question “How long will you live?”, our minds turn instinctively to the related, and more pressing question: “How can we live for longer?”
We have been trying to extend our lives for as long as we have been able to record our thoughts. Mythology abounds with stories of magical objects that grant those who possess them eternally youthful immortality. Celtic lore told that immortality would be conferred on those who ate food from a magic golden cauldron; after the Celtic conversion to Christianity this belief morphed into the legend of the holy grail. An ancient Indian myth told of the land of Uttarakurus where the Jambu tree grew; those who ate the Jambu fruit would be protected from illness and old age, and would live for thousands of years. The Mesopotamian epic of Gilgamesh described how the Uruk king went in search of an thorny underwater plant which carried rejuvinating powers. Gilgamesh managed to obtain the magical plant, but it was stolen by a snake as he bathed. The snake gained the long sought immortality, which we can see as he sheds his skin to be born anew.
To what extent do these legends contain a kernel of truth? No extension of life brought about by a magical fruit, golden chalice or aquatic bramble has ever been recorded. Nonetheless the possibility of objects conferring rejuvenation has been the driving force behind some of history’s most bizarre therapies. Roger Bacon, the thirteenth century English philosopher-scientist, proposed that amongst other things pearls, the bone of a stag’s heart and the breath of young male virgins could slow or reverse ageing. In the late 19th century the French physiologist Charles-Edouard Brown-Séquard claimed to have discovered another rejuvenating substance: essence of crushed bull testes. Eugen Steinach, a Viennese professor, expanded this idea in the 1920s; he claimed the secret of immortality lay with the grafting of younger men’s testes onto those of older men. Other cures for ageing have included exposing the rich and elderly to X-rays, radium, and hormone injections. The mere fact that history is so liberally scattered with these anecdotes – and has recorded the deaths of their proponents – is testament to their fallibility. But the desire to believe is strong, and our enlightened century is no different. High streets abound with shops stocking the latest in 21st century crushed bull testes: antioxidants, enzymes, vitamins and minerals bound in convenient one-gulp pill forms.
Is this cynicism justified? Does the fact that we are yet to uncover a substance which confers immortality, or at least significant increases in longevity, mean that it is impossible that one should exist? The most probable, and disheartening answer is: yes.
First, let us examine what constrains our lifetimes. Assuming we do not succumb to disease or die in an accident, our longevity is determined by the interaction between our genes and our environment. Ageing is an innate function of our genes: there are evolutionary reasons that underlie why we age, and how fast it happens to us; consider the fact that all animals age but elephants do so at a much slower rate than mice. Our genes also carry predisposition for disease. But our lives are not conducted sitting still in a vacuum: whatever our innate genetic longevity potential is, our actual longevity is determined in conjunction with environmental factors. We can either shorten it through either the indulgence of enjoyable vices or lengthen it through virtuous habits and access to good medicine. Or at least, that’s what we think. It is important to note that no virtuous habit is actually guaranteed to lead to an extension in life. At most, they simply reduce some of the chances that we will fall prey to a genetic trap; for example a genetic predisposition to heart disease may well have no impact on a person’s life if they never allow themselves to become an overweight smoker. But it does not then follow that all overweight smokers have heart disease, or will die from it.
Nonetheless, the feeling that we can do something to alter our longevity, to bring ourselves up to our full genetic potential – whatever that is – is a strong one. We are conditioned to think that our health is entirely in our control, when actually it is as much due to random genetic luck as it is to our daily apple consumption. This fear of our own actions limiting our longevity is the feeling which purveyors of supplements seek to capitalize on. Supplements offer a solution: an effortless way of making up this perceived deficit between what we should be doing to attain maximum longevity, and what we actually do. Those who tout these wares are implicitly – and fallaciously – selling ageing as a disease of deficiency. Let us consider their claims.
Firstly there is often no guarantee that these modern day elixirs have any effect. A good example is that of antioxidants. A long held view on the underlying causes of ageing is that of the ‘free radical damage theory of ageing’. First proposed by Denham Harman in 1956, this theory proposes that ageing is caused by oxidative damage in cells. Free radicals are highly reactive molecules which are produced during cellular respiration. Some are mopped up by the cell’s defensive enzymes (antioxidants), but most bounce around damaging important parts of the cell such as DNA. Proponents of this theory believe ageing arises from an accumulation of this oxidative damage within cells. Whilst it is true that free radicals damage cells, it is not true that this damage necessarily underlies ageing. The battle for truth rages on in labs across the world, but those who wish to make easy money choose to ignore the debate. Instead, stores market hundreds of different antioxidant pills which claim wildly different things from “increasing the brain’s energy” (huh?) to the wondrously all-encompassing “protects against damage and disease”. Having browsed through the myriad of offers online, it is clear that very few of the products advertised can give a clear reason behind why antioxidants may be beneficial… beyond being ‘natural’ of course.
Let us now consider the case of a supplement which has been shown to be beneficial in clinical trials. Leaving aside the potential for poor design, analysis and reporting of such trials, there remains great potential for overestimating the efficacy of such a supplement. This is explained particularly well by Olshansky and Carnes in their book ‘The Quest for Immortality’, and the following example is taken from them. Imagine a trial testing if vitamin E confers a health benefit to women. Half of the women received a dose of vitamin E, the other half receive a placebo and neither the women nor the doctors giving them the dose know who is getting what (the trial is double-blinded). It is discovered that the women who get daily doses of vitamin E have 40% fewer heart attacks than those in the placebo group. The trial is held up as a demonstration for the health giving properties of vitamin E; cue rushing to the local supplement store for Value Packs of the elixir. But before you start blowing your ISA on vitamin E, let’s consider what the probability of being a healthy women who is struck down by a heart attack actually is.
In the United States about 30% of all women will experience symptoms of heart disease. Let us assume for convenience that the study treated 1000 women, of whom 500 would have received the placebo and 500 the vitamin E supplement. Of the 500 receiving the supplement, only 30%, or 150 women, would be expected to be vulnerable to heart disease in the first place. Of those 150 women, only 40% (or 60 women) would have avoided heart attacks as a result of the supplement. Now, for those 60 women, the supplement did indeed benefit them. Their particular genetic predisposition for heart problems that can be ameliorated by vitamin E meant that the supplement may well have saved them. Nonetheless, we are still left with 440 women for whom the supplement had no effect, either because they weren’t at risk of heart problems in the first place, or because their particular heart problems required another intervention.
Olshansky and Carnes compare this to playing the lottery. Most of the time, most of the people who play the lottery end up losing. Those that do win will win big, but the highest likelihood is that it won’t be you or anyone you know who does win. This leaves you with two options. The first one requires you to have an excellent gag reflex and large wallet: buy and swallow every pill or potion you can find in the hope that it may be a partial cure for an ailment which you may have. Tread carefully if you do follow this approach because it’s unlikely that all the supplements on offer will have undergone good double blind clinical trials like Vitamin E one detailed above. The other approach is to not bother with any supplements and wing it. Chances are, whatever approach you take, you’ll end up living for the same time.
In the beginning of the 20th century a citizen of the United States could expect to live for approximately 45 years; today his life expectancy would be around 78. This 33 year extension in life is not owed to any fundamental change in human biology, nor the discovery of any wonder drug. Instead, advances in basic sanitation over the century have greatly reduced the risk of contracting an infectious disease and dying as a result of it. This simple change to our environment has greatly increased our longevity potentials. Until such time as we can manipulate our genetic makeup in the same way, we will be unable to replicate such an advance. Instead, our individual genetic variations, combined with efficacious medicine and healthy habits, must determine the duration of our time on this planet.
The urge within us to look for a quick fix to fend off the grim reaper is what keeps dodgy pill dealers in business. Some supplements do doubtless help some people in some situations. But the possibility of discovering a one-size-fits-all potion which can grant everyone the longer, healthier life we crave is vanishingly small. Continue to look askance at people offering you essence of bull testes. It will not do what it says on the tin.
Much of this post was taken after reading The Quest for Immortality by S. Jay Olshansky and Bruce A. Carnes. It comes with a qualified recommendation: they do some stuff well, some stuff very well, and some stuff rather badly. It’s a nice introduction to the science of longevity.
AGEING AND ANTIOXIDANTS:
A recent primer comes from Scientific American magazine, discussing the current questions about antioxidant research. A disclaimer: my PhD supervisor was David Gems. The article can be found here: http://www.ucl.ac.uk/~ucbtdag/Wenner_2013.pdf
MYTHOLOGY AND AGEING:
Gerald Gruman “A History of Ideas About the Prolongation of Life” is a wonderful, careful work which goes into great detail about the ways in which people have tried to live longer. I am only about 10% of the way through. Has many delicious titbits; recommended.
 This land, possibly located in the Himalays (very few lands of immortality have ever been located within easy reach), was famed for its other unorthodox botany; the fruit of other trees therein included precious stones and virginal maidens.
 For those that remember GCSE chemistry, they get so reactive because they have a single unpaired electron which makes them want to react with everything
 I would recommend Ben Goldacre’s excellent and terrifying book ‘Bad Pharma’ if you’re interested in these details, but don’t expect to sleep for a while…