Few of the
nutrients in food attract a more negative agenda than sugar. I recall early in
my career a famous or, in hindsight, an infamous book entitled “Pure, White and
Deadly” written by John Yudkin, then Professor of Human Nutrition at the
University of London. Not a year has gone by since then, that sugar and its
attendant industry, has not been strapped to the whipping post for a thorough
reminder of its evil properties. One of the most recent was a ‘Comment’ in
Nature which equated sugar with alcohol as a substance of abuse and addiction
meriting the guiding hand of Miss Nanny State to help us free ourselves of its dangers,
through tax and other regulatory measures. In relating sugar to alcohol, the
first parallel is that there is now unfettered access to a high sugar diet,
which according to the authors, is a new phenomenon. They write thus: “First, consider unavoidability. Evolutionarily,
sugar was available to our ancestors as fruit for only a few months a year (at
harvest time), or as honey, which was guarded by bees. But in recent years,
sugar has been added to nearly all processed foods, limiting consumer choice”[1].
If I got that in an essay from an undergraduate, I would
have annotated it with the letters “WTF”. (If you don’t get that, then simply
Google it [2].)
The missing
bit is somewhere in between “our ancestors” and “in recent years”. Honey, was
one of the great luxury foods, bees or no bees, for centuries. Virgil wrote
about it thus: “Next I come to the manna,
the heavenly gifts of honey…one that can load me with fame”. The God Zeus
was fed from childhood on honey. Sugar cane came later but well over 1,000
years ago, first recorded in T’ang dynasty (AD 766 to 790). The first known industrial
sugar cane refinery was built on the Greek island of Crete in 1000 AD, the
island of Crete being known as Qandi
in Arabic, hence the name Candy[3]
(bet you didn’t know that)!!! So
sugar didn’t suddenly appear in the last few decades.
One of the
problems linking sugar with health is that the term sugar is a chemical term
referring to a very specific group of chemicals called “saccharides”: “Any of a series of compounds of carbon,
hydrogen, and oxygen in which the atoms of the latter two elements are in the
ratio of 2:1, especially those containing the group C6H10O5”.
Glucose is the most abundant saccahride and because it is alone, single in
the sugar world, it is a monosaccharide. Fructose is next and then we meet
disaccharides where sugars are paired off. The most abundant pairing is glucose
with fructose and that is what we know as “sugar”, in the sense of the white crystalline
material in the sugar bowl. Simple? You would think so but my UK colleagues
have managed to create quite a complex issue from this, fortunately not
followed by many other countries. Let me explain. Here I am at my breakfast
table. In front of me is a bowl of oranges, which contains one less orange that
two minutes earlier, since I took one of the oranges, cut it in two and used a
manual juicer to extract the juice. That juice is in a glass on my right. Now
according to the UK authorities, the sugar in the orange in the bowl in front
of me is an “intrinsic” sugar, a natural part of the plant. The fact that I
made juice from it means I changed the sugar from being intrinsic to being “extrinsic”,
that is a sugar outside its natural plant environment, which now lies in the
glass to my right. The UK decision to adopt these definitions was not based on
extensive epidemiology, which showed that intrinsic sugars were “good” and
extrinsic sugars were “bad”. Rather, it was based on the general negative
nutritional view among some (ideological rather than scientific in my analysis)
that “sugars are just plain bad” and the need to square that stance with the belief
that some foods, which were definitely “good”, such as fruits had sugar in them.
So there had to be good sugars (intrinsic) and bad sugars (extrinsic).
When the
epidemiological evidence linking sugar intake to obesity emerged as completely
inconclusive, a new concept evolved to the effect that glucose, one item of the
sucrose pair, was probably ‘ok nutritionally” (they had little choice here
since starch is digested and absorbed as glucose and starch was a very “good”
carbohydrate) but that the other half of sucrose, namely fructose was the real
culprit. According to the Comment
in Nature, sugar compares almost precisely with alcohol in its effects on
humans. In a table entitled “Excessive consumption of fructose can cause many
of the same health problems as alcohol” they list conditions such as high blood
pressure, heart disease, impaired glucose function, obesity, pancreatitis,
liver disease (fatty liver) and addiction (habituation) to chronic fructose
intake. Frankly, these are extreme views based largely on (a) the extrapolation
of animal studies with extreme diets to humans and (b) association studies in
human nutrition epidemiology, which have not been subject to verification with
dietary intervention studies. Take one example, chronic fructose intake and
obesity. A major study, which reviewed all known intervention studies
(n=41 studies) of the chronic effect of dietary fructose on obesity in humans,
was recently published by some of the world’s most respected specialists in
carbohydrate nutrition, a study fully funded by the Canadian Institutes of
Health Research with zero industry funding[4].
I report their conclusion in full: “Fructose
does not seem to cause weight gain when it is substituted for other
carbohydrates in diets providing similar calories. Free fructose at high doses
that provided excess calories modestly increased body weight, an effect that
may be due to the extra calories rather than the fructose”. So this
independent review of the direct effect of chronic intake of fructose on
obesity finds the villain innocent. Will that placate the naysayers of sugar in
human nutrition? Not at all. However, I would once again remind them of my
favourite quotes to those who resolutely adhere to pet theories. Addressing the
Assembled Church of Scotland, Oliver Cromwell exorted them so: “Gentlemen, in the bowels of Christ, I
beseech thee, think it possible you may be wrong” or Sir Peter Medawar,
Nobel Laureate in immunology who wrote in his book “Advice to a young
scientist”: “The intensity with which an
hypothesis is held to be true has no bearing on its validity”. And finally,
from Professor Rose Frisch, the subject of last week’s blog whose work was
always controversial when she was asked how did her work finally reach
acceptance, she replied: “Funeral by
funeral”!!
Whipping sugar
is popular. It makes people feel good, it is good media friendly and it is a
joy to ministers for health who would rather discuss anything bar waiting
lists. But it is rooted in
atrocious science with one exception, dental caries. Sugar is to be enjoyed and
if you’re watching your weight, artificially induced sweeteners are to be
enjoyed. My religious friends tell me, that sugar hasn’t yet reached the sinful
threshold.
[1] Lustig, RH et al (2012)
“The toxic truth about sugar”. Nature, 482,
27-28
[3] “History of Food” by
Maguelonne Toussaint-Samat, Blackwell, Oxford
[4] John L. Sievenpiper, et al
(2012) Effect of Fructose on Body Weight in Controlled Feeding Trials - A
Systematic Review and Meta-analysis. Ann Intern Med. 156:291-304.
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