For those of us who are
concerned about our diet, the 21st century is a confusing time to
live. Almost every day there is a new food fad in the newspapers,
usually contradicting the one we read about yesterday.
If butter is bad today, it will be good tomorrow. If coffee is
harmful today, it will be beneficial tomorrow. If alcohol is
damaging today, then a glass of wine will be recommended tomorrow.
And so on. So what are we to believe? What should we be eating for
a healthy human existence? To find the answer, we have to turn the
clock back to prehistoric times and examine the way our species has
evolved over the past few million years. Our remote monkey
ancestors thrived on a diet of seeds, roots, fruits, berries, nuts,
eggs and insects. When our earliest forebears came down from the
trees and began to walk on their hind legs, their front legs were
freed from locomotion and their hands became specialized as
weapon-carriers. In this new state they began to scavenge for meat
and soon to hunt for themselves. The better they became as hunters,
the greater was the proportion of meat in their diet. This protein
boost had a major impact on their success and the human species, as
a cooperative hunter/ gatherer, was soon spreading out across the
planet and heading eventually for global domination.
As this happened, human nutritional requirements underwent certain
changes. Our physiology came to favour the special amino-acid
balance found only in meat. Proteins obtained from plants are
usually deficient in at least some of the eight amino-acids
obtained from carnivorous food. So it became possible for us to
thrive on an omnivorous diet - one that included both meat and
vegetable food. This appears to have been a genetic change and not
merely a cultural one. This information upsets some vegans who
claim that their meat-free
diet is superior to a mixed, omnivorous one. The biological truth
is that a vegetarian diet is greatly inferior to a mixed,
meat-and-veg one and it is worth pointing out that, if vegetarians
and vegans are avoiding meat because of their concerns over animal
welfare, this means that their sacrifice is even greater than they
admit. Not only do they give up the pleasures of eating meat, but
they are also prepared to stick to their principles despite the
fact that they are forcing themselves to accept a diet that is
imperfect for the digestive system of a human being. This does not
weaken their moral position: it makes it even stronger. The mixed
meat and vegetable diet of the hunter/gatherer tribes depended on
success in the hunt. Inevitably this was variable and the result
was a feast-or-famine mode of existence. Then, about ten thousand
years ago, farming appeared, cereal crops were cultivated and wild
animals were penned and domesticated. This not only made the food
source more reliable, week by week, but it also resulted, for the
first time, in a food surplus and food storage.
The reliability of this agricultural system is with us still, in
our modern industrialized towns and cities. It means that, instead
of swinging back and forth between feast and famine, we have the
chance to enjoy regular meals. The backlash from this change is the
risk of obesity. As hunter-gatherers we developed the ability to
lay down extra layers of fat beneath the skin - fat that would see
us through the periods of famine. Without such periods, our modern
citizens lay down fat but do not then use it up. Then they lay down
more fat and again do not use it up. The result is that in the more
affluent cultures there is a tendency to become overweight.
Among poorer countries another problem arises - the consumption of
a diet that favours cheap cereal foods over expensive meat foods.
With the balance between protein and carbohydrate upset, the Third
World manages to struggle on and breed successfully in large
numbers, but without the nutritional balance appropriate for the
human species. In some cultures, where careful studies have been
made, it has been discovered that the meat content of the diet has
fallen from 70% to a mere 5% in the past ten thousand years. All
over the world, the poorer populations have come to rely more and
more upon the food products obtained from five basic cereal crops -
maize, rice, wheat, manioc and millet.
Humans are so resilient that they can survive this dramatic change,
but it is far from ideal, especially in the case of infants,
children and pregnant and lactating mothers. Human beings have
simply not had the evolutionary time to adapt to this major
nutritional shift. And it is not just a surfeit of non-meat foods
that has caused us problems. In addition, mass production of
foodstuff has often tended to oversimplify our diets, removing or
drastically reducing the amount of trace-elements, minerals and
vitamins that we need for robust health. A simplified,
cereal-dominated diet, so widespread today, has created a serious
health risk to the omnivore that is the evolved human being. It
should be obvious from all this that, biologically speaking, the
ideal diet for any human being is one that is as varied as
possible, with a rough balance between protein-rich meats and
carbohydrate-rich vegetables. If we are to learn from our ancient
ancestors, we should keep on trying varied foods as often as
possible - new fruits, different kinds of nuts, berries and roots
as the seasons pass and different meats, too - fish, shellfish,
fowl and flesh in as many forms as we can find. That is the safest
way to avoid the nutritional deficiencies caused by so many
‘over-simplified’ modern diets. We evolved as omnivores
and ‘omni’ means ‘all’.
So, to return to the opening point: What are we to make of all the
new food fads we read about in the papers? It seems to me, as a
biologist, that there are three answers. First, ignore them all and
eat as wide a variety of foodstuffs as possible. That is our
evolutionary, genetic heritage. Second, if we wish to lose or gain
weight, simply eat a little more or a little less and take exercise
- that’s all there is to it! But when eating more or less,
ensure that the variety of foodstuffs consumed is maintained.
Third, avoid over-indulgence in any one particular kind of food or
drink. Too much of any one thing is unnatural and can be dangerous.
A little sugar, a little coffee, a little alcohol are beneficial.
An excessive amount of any one thing can kill.
Finally, it is important to banish all forms of anxiety from the
food table. High-stressed anxiety over obtaining a perfect diet
does more harm than an imperfect diet, which is eaten happily.
‘A little of what you fancy does you good’ goes the old
saying and there is a special reason why this is so. Anxiety over
matters of diet creates a tension in the body that lowers the
immune system and this in turn makes the individual more
susceptible to disease and ill-health. The highly-strung dieters,
nibbling nervously at some unpalatable so-called ‘health
food’ are probably in such a stressed condition that they are
undoing all the good that their ‘improved diet’ is
supposed to bestow on them. Enjoying one’s food is a good way
of ensuring a long life. A few years ago I was able to attend the
121st birthday party of Madame Jean Calment - the oldest person who
has ever lived. Right to the end she enjoyed rich Mediterranean
stews and cheap red wine. How do you manage to keep so fit? I asked
“It is because I am so calm,” she replied. “That
is why they call me Calment.”
So the next time you sit down to dine, don´t agonise over it,
try to calmly enjoy it and, who knows, you too might live to be
121.
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