The World Turned Upside Down: The Second Low-Carbohydrate Revolution (19 page)

"...nobody
has ever been admitted to a hospital for an overdose of fructose."

It is possible that sugar
and ethanol have behavioral
effects in common, but this is not due to similarities in
metabolism.  And
even the behavioral effects are not settled within the psychology
community;
alcoholism is far different from "sugar addiction," if there is such a
thing;
polishing off the whole bag of chocolate chip cookies may not
technically
qualify as addictive behavior.

In the end, nobody has ever been
admitted to a hospital for
an overdose of fructose. People may say that your diabetes was caused
by
fructose but you can't be admitted to a hospital on somebody's opinion
of what
you did wrong. There is no diagnosis "fructose poisoning." If you are
admitted to the hospital for type 2 diabetes, that is the diagnosis.

The Threat of Policy

All of this might be okay; the
numerous
scientific papers that
find something wrong with fructose probably have little impact on
people's
behavior, but, possibly for that reason, the fructophobes have gone to
the next
step. Convinced of the correctness of their position, they have taken
the case
to politicians who are always eager to tax and regulate. There is an
obvious
sense of
déja-vu
as another group of experts tries to use the American population as
guinea pigs
for a massive population experiment, along the lines the low-fat fiasco
under
which we still suffer (not to mention the example of Prohibition). It
is not
just that we got unintended consequences (think margarine and
trans
-fats)
but rather
that, as numerous people have pointed out, the science was never there
for
low-fat to begin with (brilliantly explained in
Tom
Naughton's F
at Head
).
In other words, leaving aside the
question of when we should turn science into policy, is the science any
good?

Fructose in perspective

So where are we on fructose? It is
important to understand that
fructose is not a toxin. There is no such thing as
"fructose-poisoning."
Contrary to popular myth, the "
Twinkie
Defense
," did not argue that the defendant was
possessed by some kind
of sugar rush. The defense claimed that he was propelled to homicide by
his
depressed state and that this deranged mental condition was indicated
by his
consuming junk food. (He had previously been a health-nut). Strange
defense in
that most of us think of depressives as going for suicide rather than
homicide,
but in any case, sugar did not make him do it.

Some restraint is necessary.
Alcohol-associated liver disease is
a well-characterized life-threatening condition, and, in fact, many
people do
die from it. The idea that fructose can have the same effect has no
basis in
science and is deeply offensive to people who have had personal
experience with
alcohol-related illness and death.

Fructose is a normal nutrient and
metabolite. It is a
carbohydrate and it is metabolized in the metabolic pathways of
carbohydrate
processing. If nothing else, your body makes a certain amount of
fructose. Fructose, not music (the food of love), is the
preferred fuel of
sperm cells. Fructose formed in the eye can be a risk but its cause is
generally very high glucose. The polyol reaction involves sequential
conversion
of glucose to sorbitol and then to fructose. One truly bizarre twist in
the
campaign against fructose is the study by Johnson and coworkers
[58]
that attempted to show the
deleterious effects of
glucose were due to its conversion to fructose
via
the polyol reaction. The paper is
technical but many people reading the paper published in
Nature
don't think that
the conclusion really follows from the data. If the idea is not
actually
excluded, it sounds much like an expression of the need to say that
somehow or
other everything bad is caused by fructose.

Our review, "Fructose in perspective"
was published in 2013
in
Nutrition
&
Metabolism
(available without subscription at
http://bit.ly/1i5svGR
).
Our conclusion:

"We all agree that reducing sugar
intake as a way of
reducing calories or limiting carbohydrates, is a good thing,
especially for
children, but it is important to remember that fructose and sucrose are
carbohydrates. We know well the benefits of reducing total
carbohydrate. How
much of such benefits can be attributed to removing sugar is unknown.
The major
point is that these sugars are rapidly incorporated into normal
carbohydrate
metabolism. In some sense, any unique effects of sucrose that are
observed are
due to fructose acting as a kind of super-glucose."

That was our general take on the
problem. It is frequently
said, however, that our metabolism is not designed to handle the high
input of
fructose that was absent in our evolution and that is present in what
is
frequently called our toxic environment. Although fructose may not have
been
widely available in Paleolithic times, that doesn't mean that high
consumption
was not common. It is likely that, for our ancestors, finding the rare
berry
bush was like finding a coupon for Haagen-Dazs. Moderation was not the
key
word. This was probably true of all carbohydrates, accounting for the
likely
low satiety of  the wild corn that accidentally got popped in
the forest
fire.

While few would argue that the
wide-availability or high
consumption is without risk, it is important to hew to the science.
There is a
big difference between saying that continued ingestion of high sugar
(or high
carbs, or high anything) is not good and saying that we do not have the
metabolic machinery to deal with high intake. In other words, that sugar is a foreign substance.

Again, the threat is thinking that
fructose is sufficiently
different from glucose that substituting glucose for fructose is
guaranteed to
be better. It's not. Our review was a technical analysis of the
literature
summarized in a rather complicated figure showing what is known of the
two
sugars. It may not be easily accessible to everybody but Figure 8-3 is
an
annotated version of that figure explaining some of the key general
points.

Fructose and glucose follow separate
paths...initially but
both six-carbon sugars are broken down to three carbon fragments, the
triose-phosphates. These are the intermediates in the effects of high
carbohydrate ingestion – high plasma triglycerides and low HDL ("good
cholesterol"). The conundrum for anybody who wants to attribute special
properties to fructose is how an atom in a triose-phosphate knows
whether it
came from fructose or glucose. Of course, it doesn't, and the
outstanding
feature of fructose metabolism is that it is part of glucose
metabolism.

Figure 8-3
.
Hepatic fructose metabolism

The sequence of blue arrows in Figure
8-3 shows the path by
which fructose can be turned into glucose and, under the appropriate
conditions, into glycogen. As much as 60 % of ingested fructose can be
converted to glucose via gluconeogenesis. So, is there really no
difference
between fructose and glucose? It turns out that the differences are
small and
due to kinetic (rate) effects rather than overall pattern of
processing.
Fructose is rapidly processed. Technically, fructokinase has a low Km.
That
means that it doesn't take much fructose to get its metabolism going at
a high
rate. The carbons from fructose appear in the triose-phosphates very
quickly so
that, if one wanted to make a grand statement, it might be that
fructose is a
kind of "super-glucose.

"As
much as 60 %,of
ingested fructose can be converted to glucose via
gluconeogenesis." 

It is not academic. We need to know
whether sugar acts
mostly as a carbohydrate. Again, if we remove sugar and replace it with
starch,
how will the effects compare to the results from the many trials
showing
benefits of removing carbohydrate across the board and replacing it
with fat?
In fact, nobody has directly made the comparison. The experiment has
never been
done.

Do we have the same rush to judgment
that we had with fat?
We said that dietary fat would give you heart disease and a cascade of
changes
in medical practice flowed from that. But it had never been shown that
fat
gives you heart disease. And it still hasn't been shown. A whole
society went
all out to replace fat with carbohydrate. Somehow this led to an
increase in
obesity and diabetes and the benefit to cardiovascular disease was
questionable
at best – survival improved because of treatment and any reduction in
incidence
was more likely due to reduction in smoking. The conclusion of our
review on
fructose is: "Dietary carbohydrate restriction remains the best
strategy for
obesity, diabetes and metabolic syndrome. The specific contribution of
removal
of fructose or sucrose to this effect remains unknown." Unknown is the
key
word.

Sweetener Consumption.

What about sweetener
consumption?  Did it really go up so
dramatically? Surprisingly, not as much as one might have
thought. 
According to the USDA, about 15 %.  One question is whether
this increase
is disproportionately due to fructose. The figures below show that, in
fact,
the ratio of fructose to glucose has remained constant over the last 40
years.  While sugar or HFCS is the main sweetener, pure
glucose is
sometimes used in the food industry and has remained at a constant 20 %
explaining the deviation from 1:1 which would be expected. There is,
however,
more glucose than fructose in the food supply. One might argue that
despite the
constant ratio, the absolute increase in fructose has a more pernicious
effect
than the increased glucose but, of course, you would have to prove
that. 
The figures suggest, however, that you will have to be careful in
determining
whether the effect of increased sweetener is due to fructose or to
glucose, or
whether it is the effect of one on the other, or the effect of insulin
and
other hormones on both. 

Scapegoats.

As a good example of the hyperbole
attending discussion of
fructose, consider an article in
Mother
Jones
by Gary Taubes and Cristin Kearns Couzens
called "Big Sugar's
Sweet Little Lies."
[59]
The article is a
well-researched and quite fascinating story of how the sugar industry
has been
pushing its products, but the analogy is made between sugar producers
and the
tobacco industry's attempts to bury any information that might cut into
profits. I suspect one does not have to look hard for industries that
try to
sell their product by underhanded means but the ethical problems relate
to the
product, not its promotion. Sugar does not functionally resemble
tobacco in any
way. Whether the reduction in cigarette consumption was a response to
financial
pressure rather than education is testable: in the first case,
reduction in
smoking should be greater in lower income economic groups and should be
opposite in the second case which is observed, for example, in Gallup
polls.
(http://bit.ly/1kWzhiE).

Figure 8-4
.
Sweetener
consumption. Source: USDA

The graphics from Mother Jones are
reproduced in Figure 8-5
which is supposed to illustrate "a significant rise in Americans'
consumption
of '
caloric
sweeteners,
'....
This increase was accompanied, in turn, by a surge in the chronic
diseases
increasingly linked to sugar." The sentence is tricky, really
illogical. It
says that "the increase" in sugar is linked to diseases "linked to
sugar." You
can't use "linked" twice. The link of chronic disease to sugar is
exactly
what's in question. The graphics in the article are also a little odd.