John_Yudkin_-_Pure_White_and_Deadly_revised_1986_OCR

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A host of
diseases
I now want to talk of a number of quite unrelated
conditions in which there is evidence of very varying strength that
sugar might perhaps be involved.
Damage to the eyes
Ophthalmologists had for a very long time wondered
whether nutrition could affect the way the eye developed,
and thereby affect such conditions as long-sightedness or shortsightedness.
There was some suggestion that short-sightedness
(myopia) occurred in children when their diets were short of
protein. The research on which this notion was based was not
considered acceptable by the experts, and there is nowadays no
support for this view. One of my colleagues, ~ogether with ~
ophthalmologist, looked at the problem by domg some expenments
with rats. They too could find no effects of diets that were
simply deficient in protein.
They then studied the effects of diets that were low in protein but
also high in sugar, the types of diets known to be common among
the rapidly increasing popUlations of the large cities in th~ poorer
parts of the world. In one experiment, they fed rats on diets low in
protein and with or without sugar. After six or seven months, both
of these groups had grown poorly compared with control rats fed
the normal high-protein diet. The investigators found no significant
difference in refraction between the normal rats and those on the
low-protein. high-starch diet, but the rats fed the low-protein highsugar
diet had a considerable degree of myopia, amounting to one
dioptre.
In a second experiment they took another three groups of rats:
one group was placed on a normal diet; the second on the 10wprotein
diet with sugar; the third group on the normal diet but wi?t
the amount restricted so that the rats grew at the same low rate as did
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A host of diseases
the rats on the sugar diet. After nine weeks there was no difference in
refraction between the groups. But by 15 weeks the sugar-fed rats
had developed myopia, again to the extent of nearly one dioptre,
compared with the normal group and with the poorly fed group.
At this point the diets of the second and third groups were
reversed. One result was that the poorly fed group, with normal
refraction up to the time of the change, became myopic within three
weeks of having started the diet with sugar. The other result was
that the sugar-fed group with myopia at the time of the change-over
did not improve during the whole of the rest of the experiment, even
though it lasted for 23 weeks after the change.
We also measured eye refraction in student volunteers who were
the subjects of one of our experiments. As before, we took a large
number of measurements before and after they were given a highsugar
diet. After two weeks on this diet there was a small but quite
significant change in their refraction - but this time it was a change
towards long-sightedness, not towards myopia or short-sightedness.
At present, we are suggesting thai the reasons have to do with the
level of glucose in the blood. Doctors have known for some time that
diabetics develop a mild but noticeable degree of short-sightedness if
their blood sugar is not properly controlled and consequently rises
to an unduly high level. We believe that this may be the cause of
the myopia occurring after a long period in our rats on the highsugar
diet; we know that such animals become mildly diabetic with
a high blood sugar and that a low-protein diet probably accentuates
the condition. In our students, the two weeks on a high-sugar diet
tended to produce a low blood sugar, as I have shown, so one would
have expected not myopia but long-sightedness.
I have already mentioned (p. IIo) that severe changes occur in
the retina of the eye in diabetes. And I pointed out that similar
changes can be produced in rats by feeding them with sugar.
Damage to the teeth
Each year, millions of teeth are extracted by dentists
from children all over the Western world. In the UK alone,
the loss is four million teeth weighing more than four tons. In one
survey in Dundee in Scotland, I 3-year-old boys and girls were found
to have an average of ten decayed teeth. More than one third of
British adults over 16 have had everyone of their teeth extracted.
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