Fructose & High Fructose Corn Syrup
Sugars are molecules like the ones shown
on the left. Sugars are "simple"
carbohydrates and they all, to varying
degrees, have a sweet taste that most
humans enjoy. It has been long-suspected
that sugars play a role in obesity, but it has
been surprisingly difficult to prove that.
Lately however, a growing body of evidence
strongly suggests that at least one kind of
sugar-fructose (or fruit sugar)- may play a
rather strong role in exacerbating obesity
and diabetes. To better understand why
fructose has taken "center stage", some
history is in order.
High Price of Table Sugar
Table sugar, called sucrose, is and has
long-been one of the most "protected"
commodities in the US. Because of a very
effective lobby in Congress, the sugar
industry has been able to keep import tarrifs
on cheap foreign sugar very high so that
the domestic sugar industry can charge a
very high price for its own. This meant that
sugar-containing soft drinks were
historically quite expensive and therefore
consumed in moderation in the US. It also
meant that there was a strong financial
incentive for industries that used lots of
sugar to develop cheaper alternatives.
It had been known for a long time that
cornstarch, which is cheap, could be
converted into glucose by boiling it in water
and adding enzymes called amylases. The
"problem" was that glucose was not a very
sweet sugar, so more was needed to
achieve the same sweetness as sucrose. In
the 1980's a process was perfected that
allowed glucose-corn syrup to be converted
into a mixture of glucose and the much
sweeter sugar fructose. This mixture was
and is called "high fructose corn syrup" and
it is a cheaper sweetener than table sugar.
Within a few years, nearly all soft-drinks
were made with high fructose corn syrup
instead of sugar. This guaranteed Coca Cola
Company bigger profits AND a bigger market
since now, because of high fructose corn
syrup, soft drinks were much cheaper.
The Obesity Epidemic in
By the 1990's, it had become
apparent that America was in the
midst of an epidemic of obesity.
While the disease was not new,
it was now striking a much larger
percent of our population and
worse, it was striking kids. As
public health experts began to
try to understand the causes of
this sudden jump in obesity, it
didn't take long to point the
finger at high fructose corn
syrup. Indeed, there is an eerie
coincidence of the introduction
of HFCS in the 1980's and a
sudden jump in rates of obesity a
few years later.
Does this mean that HFCS
caused to obesity epidemic?
No, not necessarily.
The problem is that about the same time HFCS hit the market, so did VCR's, video
games, personal computers and later, the internet-- all of these being human
activities that involve very little exercise. So it is possible that diminished exercise
and not HFCS is responsible for the obesity epidemic. Or, it could be a little of
both. It could also be that the reduced cost of HFCS allowed people to consume
more sugar than they had before and that simply by eating more sugar of any
kind, they gained weight. One thing to bear in mind is that table sugar, sucrose
(shown above) is actually a "disacharide" -meaning it is two sugar molecules
chemically bonded together. In the case of sucrose, the two sugars are fructose
and glucose. When sucrose is digested, the first metabolic step is to break it
down into one molecule of fructose and one of glucose. Thus sucrose yields a
50/50 mixture of the two sugars which is in fact very close to the composition of
HFCS-42 (42% fructose & 58% glucose). Thus, sodas made with table sugar (the
old fashioned way) are not really all that different chemically from those made
with HFCS. This argues that if there is a causal correlation between the
introduction of HFCS and obesity, it may only be related to the relative
affordability of hfcs and not to some distinctive metabolic difference.
How Could "Fruit Sugar" Possibly be Bad? Haven't People Been Eating it For
Thousands of Years?
Indeed, fruit sugar is ancient, but until HFCS, fruit sugar came with baggage
attached: fruit. It makes a big difference. All the fiber that comes with whole fruit
causes the fruit's sugar to be absorbed slowly by the body. Not so with pure
fructose. Here is a classic example:
If you fast overnight and then first thing in the morning squeeze the juice out of
an orange and drink it, you will find (if you check it) that your blood sugar level
rises very high during the hour following drinking the juice. Now, on the other
hand, if you fast overnight, wake up, take the same orange, peel the rind off and
then eat the whole thing, your blood sugar will barely rise at all. In both cases
you get the same amount of fruit sugar, but juice gets in fast, the whole fruit,
Fiber. Whole fruit is loaded with fiber. This slows down your body's ability to
absorb fructose. So even though fructose is ancient, purified sugar is not.
Specific Concerns About Fructose & HFCS
Fructose is mostly metabolized by the liver whereas glucose can be metabolized in
almost all human tissue. There is evidence that high fructose intake can cause
fatty changes in the liver reminiscent of alcoholic damage.
There is evidence that high fructose diets increase triglyceride levels in humans.
Humans tend not to fully absorb fructose so that some of it passes into the colon
where, like any undigested nutrient, it feeds colonic bacteria leading to
flatulence, diarhea, cramping and loose stools.
There is evidence that fructose may increase uric acid level in blood which can
lead to gout.
Recent studies in rats indicated that diets high in fructose caused the rats to
develop resistance to a weight-controlling hormone called Leptin that is produced
by fat cells in rats and in humans. More alarmingly still, the resistance developed
"silently"---that is the fructose fed rats did not get fat UNTIL they were given a
high-fat diet at which point they began to gain massive amounts of weight.
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