SURELY the whole thing should have been sewn up long ago. It鈥檚 been 300 years
since British sailors discovered the value of limes for staving off scurvy, and
the science of nutrition was born. Now there are charts and textbooks galore to
tell us exactly what each of us needs each day, and why: energy, protein in all
its forms, the many kinds of fats, the peculiar miscellany of essentials known
collectively as vitamins, plus a catalogue of minerals that seems to include
half the periodic table; all that plus dietary fibre. There is nothing to do
now, it seems, but dot a few i鈥檚 and cross a few t鈥檚.
Wrong. On supermarket shelves and in the labs of multinational companies a
quiet revolution is taking place. Bemused consumers are being bombarded with an
ever-swelling range of products loaded with ingredients quite alien to standard
nutrition texts. There are yoghurts containing the Shirota strain of the
bacterium Lactobacillus casei, margarines containing plant sterols.
Even everyday fruits and vegetables are being presented in a new light; for
centuries regarded as 鈥渏ust food鈥�, they are now being rebranded as handy devices
for delivering antioxidants or natural repositories of agents that have
pharmacological effects over and above their role as conventional nutrients.
It is easy to be cynical, and regard these so-called functional foods and
nutraceuticals as commercial gimmicks. Or worse, to view them suspiciously as
medicines thinly disguised as food supplements, evading regulation and rigorous
clinical testing鈥攖he modern equivalent of past centuries鈥� snake oil. And
in truth, the benefits are in many cases still contentious. Does lycopene in
tomatoes really reduce the risk of prostate cancer? The evidence is incomplete.
Do plant sterols lower blood cholesterol? Some studies say yes, others no.
Should we all be consuming 鈥減robiotics鈥� so encouraging 鈥渇riendly鈥� bacteria to
grow in our guts to protect us against disease? Again, the evidence is
mixed.
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Yet there are sound scientific reasons for taking this revolution very
seriously. These nutraceuticals may represent just the first foray into a whole
new category of nutrients that lie somewhere between vitamins that we can鈥檛 do
without and toxins that we must avoid. Plants have evolved a host of chemicals
to protect them from being eaten, and we, in turn, have evolved a tolerance to
many of them. But evolution didn鈥檛 stop there.
I believe that we may have turned many of these chemicals to our benefit, and
that our diets are impoverished without them. Nutritional science so far is
actually nothing more than a first draft. I suggest that we need to rethink the
way we farm, cook and eat. Not only that, but viewed in the light of evolution,
I think that many of the chemicals we think of as damaging drugs may well have
hidden benefits.
I arrived at these ideas by asking why we need even such well-accepted
entities as vitamins. The answer is far from obvious. Vitamins are an
extraordinarily mixed bag of chemicals, which complicate our nutrition no end.
Our dependence on them seems bizarre: no engineer would design a motor with such
an arbitrary list of extra requirements. Yet in a state of nature, vitamin
deficiency does not seem to be a problem. How do we make sense of all this?
Part of the answer, of course, is that human beings are not 鈥渄esigned鈥� at
all. We are not simple machines. We are innately messy because we have evolved.
And because all creatures are constantly exposed to the presence and the
importunities of others, we are permanently locked in what modern biologists
call an arms race.
Some of the fiercest battles are fought at the level of chemistry. Below
ground, bacteria and fungi have been slugging it out for billions of years. We
take advantage of this by creaming off an ever-increasing range of antibiotics,
those organisms鈥� principal armaments. Above ground, animals slug it out with
plants. All terrestrial animal life depends in the end on the consumption of
plants; the plants, for their part, have to have ways of dealing with the
onslaught of animals. To some extent they seek simply to outgrow the animals
that prey on them. But plants also produce an array of spikes, fibres and hairs
to make themselves unpalatable. In addition, most wild plants are toxic to some
degree.
Chemical warfare is expensive, metabolically speaking. If it were not
necessary, plants would be able to spend their hard-won energy on making seeds,
to spread their own genes. But like a beleaguered nation, they must invest
heavily in defence. When animals eat the plants, as they must (or, if they eat
meat, they rely on those that do eat plants), they in turn evolve detoxifying
mechanisms. Koalas are the supreme detoxifiers. The leaves of eucalyptus, their
only food, are steeped in toxins and noxious oils, all bound up in the toughest
fibre. But the koala appendix takes the poisons in its stride.
Here鈥檚 the twist. Evolution is supremely opportunistic. Any organ or
metabolic system that has evolved in response to any one problem is liable
subsequently to be pressed into some different service. Natural selection would
favour any individuals who could turn the costly detox mechanisms, or the
residues that they produce, to some further purpose. For such organisms, detox
would not just be a matter of cleaning up. It would become a positive bonus.
Are there examples of such a progression, from negative to positive, that
would make such musings more convincing? Indeed there are. Earth鈥檚 earliest life
flourished in an atmosphere that was almost totally devoid of free oxygen. Then,
probably around 3 billion years ago, bacteria comparable to the modern
cyanobacteria evolved a primitive form of photosynthesis, harnessing energy from
sunlight and releasing oxygen gas as a by-product. Photosynthesis works, and the
organisms that could do it flourished. Suddenly, geologically speaking, the
Earth acquired air rich in oxygen.
Oxygen is extremely reactive. It rusts iron, it turns fats rancid, it makes
fire. For creatures that did not evolve in its presence, oxygen is lethal.
Natural selection would have favoured creatures that could detoxify this awful
gas. All creatures that choose to live in the modern atmosphere contain a host
of oxygen detoxifiers.
But that, of course, was not the end of the story. We may speculate that some
organisms detoxified oxygen by exposing sugars to it. The energy thus released
was presumably wasted at first, as heat. Later, though, it was harnessed: used
to create ATP, the universal currency of energy exchange. Thus was born aerobic
respiration. Oxygen, so lethal because it is so fiery, was put to good use.
A similar process, I suggest, explains our reliance on vitamins. Some, at
least, arose as toxins. Plants evolved the means to produce them because at
first this kept animals at bay. Then those animals evolved detoxifying
mechanisms in response. Later, the descendants of those first detoxifiers began
to exploit the toxins themselves, or their breakdown products. These attempts to
cope with plant toxins, I suggest, have left us with the need for vitamins.
Now apply this notion more broadly. We know that plants between them produce
an astonishing pharmacopoeia of recondite chemicals, often in the spirit of
self-defence. What they do to us, or for us, depends on where we鈥檝e got to in
the arms race. A great many materials that plants produced as toxins still
poison us: here, the arms race favours the plants. At the other end of the
spectrum are the vitamins that have become as vital to us as oxygen.
Somewhere between the two extremes lie a host of pharmacologically active
agents that affect us to some extent, but are not generally lethal except when
taken in very high and unlikely doses, and yet are not absolutely vital either.
These materials include all those that have long been recognised as 鈥渢onics鈥�:
everything from camomile tea to ginseng鈥攊ndeed embracing a great deal of
traditional, herbal medicine. But also, near the vitamin end of the spectrum, is
the growing list of beneficial but not absolutely vital materials that are now
being classed as nutraceuticals or functional foods. Our bodies have come to
terms with them, evolved ways of using them, but are not absolutely
dependent.
If nutraceuticals are so important, why has it taken so long to discover
them? Many reasons. In part, there鈥檚 simply a lot to find out. Knowledge even of
the recognised vitamins has been hard won. The notion that lack of folic acid in
pregnant women might predispose to spina bifida has been verified only in the
past few decades. (I attended a meeting in the 1970s at which doctors discussed
the ethics of conducting a controlled study of the role of folic acid, given
that its role in protecting fetuses was already strongly suspected).
Nutraceuticals might be seen as 鈥渜uasi-vitamins鈥�, with many obscure effects. It
is good to lower the blood cholesterol, as plant sterols seem to do. But most of
us live to reproductive age and beyond even if our cholesterol is higher than is
ideal. It is a tribute to modern pharmacology that the effects of these plant
chemicals have been noticed at all. A few extra years of life or a slight but
significant improvement of mood, for example, would be even more difficult to
detect. How much more is there to be found out?
Although specific tests have yet to be done, if the thesis is true then the
implications are immense. To begin with, the host of companies now involved in
nutraceuticals stand to make billions, and perhaps deserve to. They may be onto
something big. Yet there are far broader implications. For the thesis suggests
that human beings need a huge variety of chemicals that are made by plants and
fungi and microbes that are as yet unquantified or even unsuspected. People
gathering plants from nature achieved this in passing: a hunter-gatherer鈥檚 diet
typically included scores of species, most of them shot through with tannins,
terpenes, alkaloids, oils, and all the rest.
Modern diets are based on just a few domesticated plants which in general
have been bred not for their biochemical variety but for yield and succulence.
Biochemically speaking, modern crops tend to be far blander than their wild
counterparts. In general, then, I suggest that modern, agricultural human
beings, are 鈥減harmacologically impoverished鈥�: deprived of that host of
quasi-vitamins that our physiology has evolved to make use of.
The real message, perhaps, is that we should revert to a more 鈥減rimitive鈥�,
botanically far more varied, diet much closer to the diets not simply of our
hunting-gathering ancestors, but of our pre-human ancestors. All the world鈥檚
agriculturalists, both breeders and farmers, and indeed the world鈥檚 chefs,
should go back to the drawing board. Indeed, the whole of herbal medicine needs
looking at again in the light of this idea.
We might also apply a little evolutionary thinking to the great b锚te
noire of our age: 鈥渄rugs鈥�. Behind the official condemnation of opiates and
cocaine, alcohol and nicotine, marijuana and caffeine鈥攁nd the undoubted
dangers that their misuse can pose鈥攍ies the largely unexplored conceit
that 鈥渄rugs鈥� in general must be bad. Yet our brains, like our bodies, evolved in
the presence of weird, extraneous materials made by plants and mushrooms. We
know from experience that if we expose ourselves to some of them, we perceive
the world differently.
Puritans, along with most modern lawmakers and medical scientists, feel that
any deviation from the most unadulterated baseline in what we ingest is by
definition abnormal. But our ancestors, gathering wild plants, must have been
steeped in these recondite materials. Perhaps our brains work best in their
occasional presence, just as our bodies work best in the constant presence of
oxygen. Perhaps our brains, like the rest of us, are 鈥減harmacologically
impoverished鈥�. Maybe there is survival value in looking at the world from
different points of view at different times; perhaps the agents that we
recognise and have often condemned as 鈥渄rugs鈥� help us to do this.
Many people with no criminal or otherwise pathological tendencies adjust the
tenor of their lives by judicious intake of alcohol, caffeine and nicotine. Is
it because they are 鈥渨eak鈥�, as puritans have maintained, or because that鈥檚 the
way the human brain works best? Perhaps we should ask whether the current often
hysterical war against 鈥渉ard鈥� drugs is really appropriate鈥攁nd I write as
one with almost no exposure to any drug less respectable than Glenmorangie.
Only in recent years, 140 years after Charles Darwin laid out the idea of
natural selection in On the Origin of Species, has it become
fashionable to apply elementary evolutionary thinking directly to day-to-day
human affairs. When applied to nutraceuticals, such thinking suggests that they
are not mere hype. They could be the start of an even more exciting era in
biology than we have yet realised.