Fructose

e transported from the mitochondria into the cytosol of hepatocytes, converted to acetyl CoA
by citrate lyase and directed toward fatty acid synthesis. Additionally, DHAP can be converted to
glycerol 3-phosphate as previously mentioned, providing the glycerol backbone for the triglyceride
molecule. Triglycerides are incorporated into very low density lipoproteins (VLDL), which are
released from the liver destined toward peripheral tissues for storage in both fat and muscle cells.
Metabolic syndromes
Excess processed fructose consumption has been hypothesized to be a cause of insulin resistance,
obesity, elevated LDL cholesterol and triglycerides, leading to metabolic syndrome. Fructose
consumption has been shown to be correlated with obesity, especially central obesity which is
thought to be the most dangerous kind of obesity. A study in mice showed that a high fructose
intake increases adiposity.
Although all simple sugars have nearly identical chemical formulae, each has distinct chemical
properties. This can be illustrated with pure fructose. A journal article reports that, "...fructose
given alone increased the blood glucose almost as much as a similar amount of glucose (78% of
the glucose-alone area)".
One study concluded that processed high fructose corn syrup "produced significantly higher fasting
plasma triacylglycerol values than did the glucose diet in men" and "...if plasma triacylglycerols are
a risk factor for cardiovascular disease, then diets high in processed fructose may be undesirable".
Bantle et al. "noted the same effects in a study of 14 healthy volunteers who sequentially ate a
high-fructose diet and one almost devoid of the sugar."
Fructose is a reducing sugar, as are all monosaccharides. The spontaneous chemical reaction of
simple sugar molecules to proteins, known as glycation, is thought to be a significant cause of
damage in diabetics. Fructose appears to be equivalent to glucose in this regard and so does not
seem to be a better answer for diabetes for this reason alone, save for the smaller quantities
required to achieve equivalent sweetness in some foods. This may be an important contribution
to senescence and many age-related chronic diseases.
Health effects
Figure 7: Metabolic conversion of fructose to triglyceride in the liver.
Digestive problems
Fructose absorption occurs via the GLUT-5 (fructose only) transporter, and the GLUT2 transporter,
for which it competes with glucose and galactose. A deficiency of GLUT 5 may result in excess
fructose carried into the lower intestine.[citation needed] There, it can provide nutrients for the
existing gut flora, which produce gas. It may also cause water retention in the intestine. These
effects may lead to bloating, excessive flatulence, loose stools, and even diarrhea depending on
the amounts eaten and other factors. For many people, fructose malabsorption is a major health
concern.
Compared to sucrose
Studies that have compared high-fructose corn syrup (an ingredient in nearly all soft drinks sold
in the US) to sucrose (common table sugar) find that most measured physiological effects are
equivalent. For instance, Melanson et al. (2006), studied the effects of HFCS and sucrose sweetened
drinks on blood glucose, insulin, leptin, and ghrelin levels. They found no significant differences in
any of these parameters. This is not surprising, since sucrose is a disaccharide that digests to 50%
fructose and 50% glucose, whereas the high-fructose corn syrup most commonly used on soft
drinks is 55% fructose and 45% glucose. The difference between the two lies in the fact that HFCS
contains little sucrose, the fructose and glucose being independent moieties.
Fructose is often recommended for diabetics because it does not trigger the production of insulin
by pancreatic ß cells, probably because ß cells have low levels of GLUT5. Fructose has a very low
glycemic index of 19 ± 2, compared with 100 for glucose and 68 ± 5 for sucrose. Fructose is also
seventy-three percent sweeter than sucrose (see 2.1 Relative Sweetness) at room temperature, so
diabetics can use less of it. Studies show that fructose consumed before a meal may even lessen
the glycemic response of the meal. Its sweetness changes at higher temperatures, so its effects in
recipes are not equivalent to those of sucrose (i.e., table sugar).[citation needed]
Liver disease
"The medical profession thinks fructose is better for diabetics than sugar," says Meira Field, Ph.D.,
a research chemist at United States Department of Agriculture, "but every cell in the body can
metabolize glucose. However, all fructose must be metabolized in the liver. The livers of the rats
on the high fructose diet looked like the livers of alcoholics, plugged with fat and cirrhotic." While
a few other tissues (e.g., sperm cells and some intestinal cells) do use fructose directly, fructose is
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