John_Yudkin_-_Pure_White_and_Deadly_revised_1986_OCR

Pure, White and Deadly
discerned about the rules that govern living processes and living
organisms.
It is logical then to spend a few minutes looking at both of these
aspects: to ascertain the kinds of evidence one can hope to find about
the causes of disease and the limitations of this evidence; and also
to see if general laws can be detected that make sense in relation to
the maintenance of health. Since I am talking in this book mostly
about sugar, and since the most important disease I shall be talking
about is heart disease, I shall refer briefly to sugar and heart disease,
but the same principles apply to any cause and any disease.
I ought also to say just a little about the word 'cause', because I
am going to talk quite a lot about sugar being a 'cause' of a number
of diseases. In the first place, it is quite certain that none of the
diseases I shall be talking about are caused by sugar in the same sort
of way that heat causes ice to melt. People differ in their susceptibility
to disease, so that even in identical conditions - supposing you could
produce them - one man might have a heart attack and another
might not. This susceptibility seems to a large extent to be inherited,
so one may say that your chances of getting a coronary are less if
your parents, grandparents, uncles and aunts have mostly lived to
a ripe old age without having the disease; the chances are greater if
many members of your family have had it.
In addition to this genetic factor, environmental factors also play
a role in coronary disease. Most people accept the proposition that
several environmental factors are influential and that these include
leading a sedentary sort of life and smoking cigarettes. What I am
hoping to show is that eating a lot of sugar is another environmental
factor (or cause) in producing heart disease. I do not propose to show
that sugar is the one and only factor involved in producing this
disease, or indeed, any disease.
One more word about causes. If an event A sets off another event
B, and if without A, B would not occur, then you can call A the
cause of B. But suppose I throw a lighted match into my wastepaper
basket, and my study and then my house burn down. Was the
cause the lighted match? Or the loose paper in my waste-paper
basket? Or the fact that my house contained lots of books and an
excessive amount of wood? If anyone of these factors had been
different, the house might not have burned down at all. Alternatively,
there might have been a short circuit in the electrical supply
to my desk lamp, so the house might have burned for a reason quite
unrelated to a lighted match.
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Can you prove it?
I could say that if I eat sugary foods I get holes in my teeth. Then
pr~sumably the sugary foods are the cause of dental decay. But I
mlgh~ not ?"et dental decay, in spite of these foods, if I have a high
genetlc ~eslstance to the dis~ase; or if I brush my teeth immediately
after eatlng these foods; or If I know how to keep my mouth free of
the ~acteria that actually attack the teeth after being stimulated to
multiply and to become active by the sugar in food. Is sugar then
the 'cause' of tooth decay? Or is it the bacteria? Or the lack of
resistance of my teeth?
So in w~at follows, I do not expect to show you that a high intake
of sugar IS the one and only cause of the diseases I mention. I
do hope to persuade you, however, that, whatever your heredity,
and however much you may persist in habits that are involved in
producing one or other of these conditions, your chances of
developing it w?uld be significantly reduced if you reduced your
sugar consumptIon.
Now what about the sorts of evidence that a particular cause
produces a particular disease? Broadly, there are two chief types of
evidence: epidemiological and experimental. By 'epidemiological', I
mean eVidence that there is an association between the intensity of
the supposed cause and the presence of the disease. Such evidence
deals with these sorts of questions:
Is heart disease more common in popUlations that eat more sugar?
If there .has been an increase in the number of people suffering
from the dIsease, has there also been an increase in the consumption
of sugar?
In any popUlation, has more sugar been eaten by the people that
actually have the disease than by those who do not have it?
'Experimental' evidence is produced when you attempt to answer
these sorts of questions:
Does the feeding of sugar to animals in a laboratory lead to heart
disease?
Does removal of sugar from the diet reduce the chances of animals
or people getting heart disease?
You may also ask rather less direct questions, such as: short of
producing the disease itself, does the feeding of sugar produce the
sorts of changes you normally find associated with the disease?
~s . to general laws,. it seems to me that one or two biological
pn~clples oug~t especla~ly to be remembered in these days of very
rapId changes In our enVIronment. First, living organisms can often
adapt to change if it is not too rapid, nor too profound. If, however,