John_Yudkin_-_Pure_White_and_Deadly_revised_1986_OCR

Pure, White and Deadly
is reason to believe that arterial disease may arise from a continuing
high level of insulin. I shall then discuss the interesting association
between diabetes, overweight and arterial disease, and the fact that
people with any of these conditions are likely to have excessive
insulin in the blood.
There are several reasons why I believe that eating too much sugar
is one cause of diabetes - mostly of Type II diabetes, but possibly
Type I too. First there is the epidemiological evidence. Much of it
parallels what I have already cited for coronary thrombosis, but here
the evidence is fraught with even more difficulties.
In some ways, one could have expected an association between
diabetes and dietary sugar, or any other environmental factor, to be
simpler than that for coronary thrombosis because diabetes is more
readily diagnosed during life. But in fact not many countries have
the facilities for the large-scale and fairly elaborate surveys that
would be needed to detect early diabetes. And as for mortality statistics,
the difficulty here is that people with diabetes often die of one
or other of the many complications of the disease, and the death
may then be certified as having been due to the complications rather
than to the diabetes itself. So science is on rather uncertain ground
about the prevalence of diabetes, and I can only give you the views
that are commonly, but not universally, held by the experts.
They believe that diabetes in the well-off countries is much more
prevalent today than it used to be. If you look for it carefully, by
checking for sugar (glucose) in the urine, or testing the level
of glucose in the blood, you can find at least mild diabetes in something
like 2 per cent of the popUlation in Western countries. Currently
it is on the whole more prevalent in these countries than in
the poorer countries. Among the people of Indian descent studied
by Dr G. D. Campbell in Natal, South Mrica, there is a much higher
prevalence than in India itself. The average intake of sugar in Natal
is said to be IIO pounds or more a year; in India it is between 15
and 20 pounds a year. Moreover, there is much more disease among
fairly wealthy Natal Indians than amongst the poorer.
One other epidemiological study worth mentioning is that of Dr
E. Ziegler of Switzerland. He compared the mortality due to diabetes
in Switzerland with sugar intake, using a rather novel method
of assessing this as the 'sugar climate' - the total amount of sugar
consumed over a period of years. He then demonstrated that the
mortality from diabetes over a period of 20 years is correlated, both
in men and in women, with this 'sugar climate'.
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Too much blood sugar - or too little
The view that diabetes may be caused by eating sugar has long
been held by many people. The name 'sugar diabetes' of course
refers to the fact that sugar (glucose) is found in the urine of affected
persons. But people also take the name to refer to dietary sugar as
a cause of the disease as well as to one of its symptoms. Again, for
more than 100 years before insulin was discovered, it was known
that diets low in carbohydrates and especially in sugar were the best
treatment for diabetes.
Yet the first detailed epidemiological evidence, put forward by
Sir Harold Himsworth some 50 years ago, suggested that the disease
was associated most closely with fat consumption. He showed that
the mortality from the disease in different couritries was often proportional
to the average amounts of fat in local diets. But he himself
expressed surprise that this was so, knowing that a diet high in fat
was the currently accepted treatment for the disease. Himsworth
wrote:
The dietary factor which parallels these changes [in
mortality and prevalence of diabetes] most closely is the
consumption of fat, and this correlation is surprisingly
consistent ••. We are thus left with the paradox that,
though the consumption of fat has no deleterious
influence on sugar tolerance, and fat diets actually
reduce the susceptibility of animals to diabetogenic
agents, the incidence of human diabetes is correlated
with the amount off at consumed.
Looking at the problem again some years later, I wondered
whether Himsworth's difficulty arose from making the common
assumption that all carbohydrate was equivalent. Since total carbohydrate
consumption is similar in most countries, there was no
reason to suspect carbohydrates as a cause of diabetes. But when
you consider the different forms of carbohydrate, then you find that
the prevalence of diabetes is more closely related to the amount of
dietary sugar than to dietary fat. This is especially true if you take
into account the probability that it may take 20 years or so for the
diet to produce diabetes, as Dr Campbell suggests.
When I related the number of people dying of diabetes in different
countries to the amount of sugar or fat that was eaten some 20 years
earlier, I found a high correlation with sugar and no correlation with
fat. The sort of relationship with fat that is sometimes found, and
was found by Himsworth, comes about because, as I pointed out,
average fat consumption in different countries is frequently related
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