John_Yudkin_-_Pure_White_and_Deadly_revised_1986_OCR

Pure, White and Deadly
limited by the methods available for carrying out the measurements.
It may be that for a particular substance either no method exists or
none that is suitable for routine use, since it may require very special
apparatus or may involve very laborious techniques. Conversely, it
may be that quite simple methods exist for measuring the substance,
even though it may not be - or may turn out not to be - very relevant
to the disease being studied.
This, I believe, is the position with studies on coronary disease.
If it is true - and I am still far from convinced - that the most
important change in this condition is the increased level of some of
the fatty materials in the blood, then there is a lot to be said for the
view of many workers that levels of other fatty substances are more
informative than levels of cholesterol. One such substance is triglyceride'
another is one of the particular compounds that holds the
choles~erol in the blood. This is the cholesterol bound to highdensity
lipoprotein ('HDL cholesterol') which is now accepted as a
better indicator of coronary risk than the total amount of cholesterol.
Indeed, not everyone is convinced that, in most people, much inf~rmation
is gained from measuring only total cholesterol. One dlstinguished
American research physician. h~s written ~a~ blo?d
cholesterol is a biochemical measurement sull ill search of clinIcal SIgnificance!
One final sort of experimental evidence is to see what will cure or
prevent the disease; from this, within reason, ?ne can draw. co~clusions
about the cause. An obvious example IS scurvy, which IS
cured by giving oranges or lemons; it was this discovery that. ultimately
led to the identification of the cause of scurvy: a deficIency
of vitamin C, which is contained in fruits and vegetables. .
But there are two possible ways in which one can be mlsled,
one obvious and one less obvious. The obvious one, though often
overlooked, is that there are some conditions, like the rheumatic
diseases, in which the symptoms fluctuate. A period of pain is frequently
followed by a period of remission, so that any treatment
given while the disease is worrying the patient is likely to be thought
to have produced the subsequent improvement. .
One can also fall into a rather more subtle trap. I can best explam
this by an example. Many older people who suffer from a variety of
diseases gradually develop a degree of heart failure, and one of the
effects is swollen legs due to dropsy (oedema). This can be relieved
if large amounts of vitamin C are taken, for the vitamin acts as a
diuretic and increases the loss of fluid through the kidneys. Yet
Can yo1f, prove it?
although this treatment is curing a symptom of heart failure, the
condition is clearly not due to a deficiency of vitamin C.
A more obvious example, if perhaps a rather ridiculous one, is
that curing a headache with aspirin does not imply that the headache
was caused by aspirin deficiency.
Let me here refer to the results of experiments on the effect of
changing the diet in attempts to prevent coronary disease. Since
these experiments have all been designed to test the effect of altering
the fat content of the diet, and not the effect of altering the sugar
content, it will be best to discuss these experiments at this point
rather than later, when I shall be concentrating on the case against
sugar. It is also useful to do this here because I shall be able to
demonstrate another of the difficulties of research into the subject
of diet and heart disease.
There have been several experiments, or trials, in which fat intake
was changed by reducing the amount of saturated fats like butter
fat and meat fat, sometimes also adding vegetable oil like corn oil.
In some trials, the doctors studied people who had already had one
or more attacks of coronary disease. The research workers tried to
see whether the change of diet reduced the patients' chances of
getting another attack compared with a similar group whose diet
had not been changed.
This sort of study is called a 'secondary prevention trial'. The
other sort of study is the 'primary prevention trial', in which the
investigators change the diet of apparently healthy men and see how
many develop coronary disease, again compared with a matched
group whose diet has not been changed.
Several trials of each sort have now taken place, the most important
being those attempting primary prevention. One was in a veterails
(ex-service) centre in Los Angeles, in which 424 men were put
on an experimental diet with reduced saturated fat and cholesterol,
and increased polyunsaturated fat. During the next five years the
researchers compared these men with 422 men whose diet was not
changed. It turned out that there were 63 deaths from coronary
disease in the experimental group and 82 in the control group; however,
the number of deaths from all causes was the same in both
groups. One unwelcome result was that more of the men in the
experimental group developed gallstones.
A trial in Helsinki lasted 15 years. This involved patients in two
different mental hospitals. In one, the patients received the standard
Finnish diet, and in the other a diet with a high proportion of