Fructose is a sugar found widely in the diet as a free
monosaccharide hexose, as
the disaccharide, sucrose
and in a polymerized form (fructans) as a component of plant oligosaccharides.
Because fructose is considerably sweeter than sucrose or glucose, it is used to enhance the
flavor, color stability, and freezing point depression of many foods and
beverages. Fructose is also used in place of sucrose and other
carbohydrates in
dietetic products.
Fructose is a simple sugar found in honey, fruit, table sugar
(sucrose), and high-fructose corn syrup. Because of the worldwide
increase in the consumption of these sweeteners, fructose intake has increase
dramatically
since the early 1900s. The past several decades have witnessed an even greater
acceleration in consumption, in part because of the introduction of
high-fructose corn syrup; this
phenomenon is associated with the rise in
obesity, diabetes, and
high blood pressure. Studies in animals have shown that fructose can induce most features of the
metabolic syndrome, including insulin resistance, elevated triglycerides,
abdominal obesity, elevated blood pressure, inflammation, oxidative stress,
endothelial dysfunction, kidney injury, and fatty liver. See natural ways to
reduce levels of cholesterol.
Is it a good thing or a bad thing?
Human and animal studies suggest that fructose ingestion produces deleterious
effects on the cardiovascular system, such as increase in blood pressure and
also has adverse metabolic effects, for example insulin resistance and hypertriglyceridaemia. On the other hand it has also been determined that
fructose, especially that is contained in natural sources as apples, dates and
honey may produce beneficial effects on human health; smaller amounts may even
help improve diabetic control. In conclusion, fructose appears to be not all
that bad; is essential for male fertility, small amounts of fructose,
specifically which comes from dietary sources appears to be beneficial for
health.
High fructose intake harm
High intake of fructose is associated with the biochemical alterations that
promote the development of metabolic syndrome, nonalcoholic fatty liver disease,
and type 2 diabetes. It is metabolized by the liver, where it stimulates the
production of fat molecules. The triglycerides synthesized lead to hepatic
insulin resistance and high lipid levels in the blood. Fructose-derived advanced
glycation end products (AGEs) can harm the body and age it quicker.
Q. I have read that sodas with sugar are harmful but recently
I was told that fruit juices are also not healthy and can raise blood sugar.
A. Sodas, sugary sports drinks and other sugar-sweetened beverages
raise blood sugar levels and increase one's risk of developing type 2 diabetes
and metabolic syndrome thus raising the risk of heart disease. What many people
don't realize is that even though fruit juices (for instance apple and orange)
have beneficial substances, they still contain lots of a sugar called fructose
which can cause similar problems as that found in sodas. Many people drink 8
ounces of more of orange juice in the morning. The sugar in fruit juices causes
a spike in blood sugar levels. I generally recommend no more than two to four
ounces of fruit juice at one time.
Fructose in diet, the foods that contain it
Most fructose in the American diet comes not from fresh fruit, but from
high fructose corn syrup or sucrose (sugar) that is found in soft drinks
and sweets.
In 1966, refined sugar, also known as sucrose, held the
No. 1 slot, accounting for 86 percent of
sweeteners used. Today,
sweeteners made from corn are the leader, racking up several billion in
annual sales and accounting for more than half of the sweetener market. That
switch largely reflects the steady growth of high fructose corn syrup,
which climbed from zero consumption in 1966 to more than 60 pounds per person
after the year
2000.
Fructose content in foods -
benefit through eating fruits as opposed to processed foods
and drinks
Honey, dates, raisins, molasses, and figs have a content of fructose
greater than 10%. Grapes, raw apples, apple juice, persimmons, and
blueberries have a fructose content of 5–10% by weight. Milk has hardly
any fructose, nor do most vegetables and meats. When fructose is ingested
from fruits, many other beneficial substances are also ingested including
fiber and antioxidants, whereas when fructose is ingested through soft
drinks or other processed foods, there is no fiber to slow the absorption
of the fructose and few antioxidants to prevent or minimize the adverse
effects of a high fructose intake on blood sugar or tissues.
Fructose absorption and metabolism
When ingested by itself, fructose is poorly absorbed from the
gastrointestinal tract, and it is almost entirely cleared by the liver.
Fructose differs in several ways from glucose, the other half of the
sucrose (sugar) molecule. Fructose is absorbed from the gastrointestinal
tract by a different mechanism than that for glucose. Glucose stimulates
insulin release from the isolated pancreas, but fructose does not. Most
cells have only low amounts of the glut-5 transporter, which transports
fructose into cells. Fructose cannot enter most cells, because they lack
glut-5, whereas glucose is transported into cells by glut-4, an
insulin-dependent transport system. Finally, once inside the liver cell,
fructose can enter the pathways that provide glycerol, the backbone for
triacylglycerol.
Fructose is easily metabolized and changed into fat. Studies in
rodents, dogs, and nonhuman primates eating diets high in fructose or
sucrose consistently show elevated blood lipids. The metabolism of
fructose in the liver drives the production of uric acid, which utilizes
nitric oxide, a key modulator of vascular function. George Bray, American
Journal of Clinical Nutrition, 2007.
A high fructose diet increases lipid deposition in liver and muscle and fasting VLDL-triacylglycerols and decreases hepatic insulin sensitivity.
Increase in cancer rate
Pancreatic tumor cells use fructose to divide and proliferate. Tumor cells fed
both glucose and fructose use the two sugars in two different ways. Dr. Anthony
Heaney of UCLA's Jonsson Cancer Center grew pancreatic cancer cells in lab
dishes and fed them both glucose and fructose. Tumor cells thrive on sugar but
they used the fructose to proliferate. Americans take in large amounts of
fructose, mainly in high fructose corn syrup, a mix of fructose and glucose that
is used in soft drinks, bread and a range of other foods. Cancer Research,
2010.
Fructose and diabetes, blood sugar
Diets high in fructose cause insulin resistance, a precursor to type 2 diabetes.
A particular gene, known as PGC-1 beta, appears to play a key role in the
development of insulin resistance in response to a high-fructose diet. Rats that
had the gene's activity blocked were protected from insulin resistance despite
feasting on a diet loaded with fructose. High-fructose corn syrup has been
widely used in sodas and processed foods since the 1980s, and some researchers
have blamed this trend at least in part for the concurrent rise in obesity and
diabetes. Some studies have shown that fructose is metabolized differently than
glucose is, being more readily converted into fat. Dr. Gerald Shulman and
colleagues at Yale University School of Medicine. looked at PGC-1 beta because
it activates another gene that governs the production of fat by the liver. When
the researchers blocked the gene's activity in rats fed a high-fructose diet,
the animals did not develop insulin resistance and elevated triglycerides.
Inhibiting PGC-1 beta could help treat some cases of high triglycerides, fatty
liver disease and insulin resistance. Cell Metabolism, 2009.
Excessive fructose intake from high-fructose corn syrup (HFCS) and sucrose has been implicated as a driving force behind the increasing prevalence of obesity and its downstream cardiometabolic complications including hypertension, gout, dyslidpidemia, metabolic syndrome, diabetes, and non-alcoholic fatty liver disease. Curr Hypertension Rep. 2013.
Diabetes. October 2013. Sugar, uric acid, and the etiology of diabetes and obesity. The intake of added sugars, such as from table sugar (sucrose) and high-fructose corn syrup has increased dramatically in the last hundred years and correlates closely with the rise in obesity, metabolic syndrome, and diabetes. Fructose is a major component of added sugars and is distinct from other sugars in its ability to cause intracellular ATP depletion, nucleotide turnover, and the generation of uric acid. Recent studies show that fructose-induced uric acid generation causes mitochondrial oxidative stress that stimulates fat accumulation independent of excessive caloric intake. These studies challenge the long-standing dogma that "a calorie is just a calorie" and suggest that the metabolic effects of food may matter as much as its energy content.
Fructose consumption and
gout
Consumption of sugar sweetened soft drinks and very high intake of fructose is associated with an increased risk of
gout in men. Fructose
rich fruits and fruit juices may also increase the risk when consumed as a
high proportion of the diet.. Diet soft drinks
are not associated with the risk of gout.
High fructose corn syrup and obesity
The intake of soft drinks containing high-fructose corn syrup or sucrose
has risen in parallel with the epidemic of obesity.
Made from corn starch, high-fructose corn syrup is a thick liquid that
contains two basic sugar building blocks, fructose and
glucose, in roughly
equal amounts. While soft drinks and fruit beverages such
as lemonade are the leading products containing high fructose corn syrup,
plenty of other items -- including cookies, gum, jams, jellies and baked
goods -- also contain this syrup.
High fructose corn syrup is produced by processing corn starch to
change its sugars from glucose to fructose. The sweetener became a popular
replacement for table sugar (sucrose) in the 1980s when pricing controls
and quotas made it expensive to import sugar into the U.S. Coca-Cola and
Pepsi switched from sucrose to high-fructose corn syrup in 1984, and many
other food manufacturers have since followed. Today, high-fructose corn
syrup is found in everything from cookies to salad dressing to breakfast
cereal. By 2005, the average American was consuming 60 pounds of
high-fructose corn syrup each year, compared with 58 pounds of sugar.
Dr. Elizabeth Parks, a physiologist and associate professor at the Center
for Human Nutrition at the University of Texas' Southwestern Medical
Center in Dallas has been studying this topic. Dr. Elizabeth Parks has
found that our bodies turn fructose into fat more readily than glucose.
Consuming too much fructose -- a form of sugar found in corn syrup, honey and fruit -- appears to alter levels of hormones involved in appetite regulation in such a way as to encourage overeating, a new study suggests.After people in the study ate a meal followed by a drink flavored with the same amount of fructose found in two cans of soda, they showed relatively low levels of insulin and leptin, hormones that help people know that they are full. On the other hand, they showed relatively high levels of ghrelin, a hormone that stimulates eating. These hormonal changes could promote overeating,. Sugar occurs in two forms, fructose and glucose. Glucose, but not fructose, stimulates insulin secretion, which in turn regulates leptin production. Both fructose and glucose are naturally found in fruit and fruit juices. However, over the years manufacturers have sweetened sodas and some foods with corn syrup, which contains concentrated amounts of fructose. To investigate whether drinking fructose plays a role in obesity, Teff and her colleagues asked 12 normal-weight women to wash down balanced meals with drinks sweetened with either fructose or glucose. When the women drank the fructose drink, their levels of insulin and leptin were lower than when they consumed a drink flavored with glucose, and levels of ghrelin were higher, the researchers report in the Journal of Clinical Endocrinology and Metabolism. In addition, drinking the fructose drink was associated with a spike in levels of blood fats, a known risk factor for cardiovascular disease.
Sucrose or high fructose corn syrup have similar effect on satiety
Sugars and satiety: does the type of sweetener make a difference?
American Journal of Clinical Nutrition, 2007.
The objective of the study was to compare the relative effect of
commercial beverages containing sucrose or high fructose corn syrup on hunger, satiety, and energy intakes at the next meal with the use of a
within-subject design.
Thirty-seven volunteers (19 men, 18 women) aged 20–29 y consumed
isocaloric cola beverages (215 kcal) sweetened with sucrose, high fructose corn syrup 42, or high fructose corn syrup 55. High fructose corn syrup 42 contains 42% fructose, and high fructose corn syrup 55 contains 55% fructose. Diet cola (2 kcal), 1%-fat milk (215 kcal), and no
beverage were the control conditions. The 5 beverages were consumed 2 h after a standard breakfast. Participants rated hunger, thirst,
and satiety at baseline and at 20-min intervals after ingestion. A tray
lunch (1708 kcal) was served at 1230, and energy intakes were measured.
There was no differences between sucrose- and high fructose corn syrup -sweetened colas in perceived sweetness, hunger and satiety profiles, or
energy intakes at lunch. The 4 caloric beverages tended to partially
suppress energy intakes at lunch, whereas the no-beverage and diet
beverage conditions did not; the effect was significant only for 1%-fat
milk. Energy intakes in the diet cola and the no-beverage conditions did
not differ significantly. There was no evidence that
commercial cola beverages sweetened with either sucrose or high fructose corn syrup have significantly different effects on hunger, satiety, or short-term energy
intakes.
Fructose -- a kind of sugar found in a wide variety of foods and beverages -- may encourage overeating. Fructose may be best known to consumers in the form of high-fructose corn syrup, which has long been added to manufactured foods from sodas to cookies. Distinct from sugar known as glucose (produced by the natural breakdown of complex carbohydrates), fructose is also a "simple" sugar and a natural component of fruit. However, "in a series of studies we have found that when compared to glucose, the simple sugar, fructose, is a weaker suppressor of brain areas that help control appetite and the motivation to eat," said study co-author Dr. Kathleen Page, an assistant professor of clinical medicine at the Keck School of Medicine of the University of Southern California in Los Angeles.
Fructose and glucose
consumption compared to whey protein ingestion
Appetite hormones and energy intake in obese men after consumption
of fructose, glucose and whey protein beverages.
Int J Obes (Lond). 2007.
Commonwealth Scientific and Industrial Research Organisation (CSIRO),
Human Nutrition, Adelaide, Australia, Department of Physiology, University
of Adelaide, Adelaide, Australia.
To investigate appetite responses over 4 hour to fructose beverages in
obese men, relative to glucose and whey protein. Second, to investigate
the effect of combining whey and fructose on postprandial appetite
hormones. Randomized, double-blind crossover study of four beverages containing 50 g of whey, fructose, glucose or 25 g whey+25 g fructose.
Blood samples and appetite ratings were collected for 4 h then a buffet
meal was offered. Subjects were twenty-eight obese men. Measurements were
done of plasma ghrelin (total), glucagon-like peptide-1 (GLP-1 7-36),
cholecystokinin-8, glucose, insulin and appetite ratings were assessed at
baseline and 30, 45, 60, 90, 120, 180, 240 min after beverages, followed
by measurement of ad libitum energy intake. Results: Fructose produced
lower glycemia and insulinemia compared to the glucose treatment; whereas
postprandial ghrelin, GLP-1 and cholecystokinin responses were similar
after both treatments. Whey protein produced a prolonged (2-4 h)
suppression of ghrelin and elevation of GLP-1 and cholecystokinin that
were reduced when combined with fructose, while glucose and insulin
responses were similar. Energy intake after 4 h was independent of
beverage type. Conclusion:In obese men, fructose- and glucose-based
beverages had similar effects on appetite and associated regulatory
hormones, independent of the differing glycemic and insulinemic responses.
The contrasting profile of plasma ghrelin, GLP-1 and cholecystokinin after
whey protein consumption did not impact on ad libitum intake 4 h later and
was attenuated when 50% of whey was replaced with fructose.
Fructose absorption
Free fructose has limited absorption in the small intestine, with up to
one half of the population unable to completely absorb a load of 25 g.
Average daily intake of fructose varies from 11 to 54 g around the world.
Fructans are not hydrolysed or absorbed in the small intestine. The
physiological consequences of their malabsorption include increasing
osmotic load, providing substrate for rapid bacterial fermentation,
changing gastrointestinal motility, promoting mucosal biofilm and altering
the profile of bacteria. These effects are additive with other short-chain
poorly absorbed carbohydrates such as sorbitol. The clinical significance
of these events depends upon the response of the bowel to such changes;
they have a higher chance of inducing symptoms in patients with functional
gut disorders than asymptomatic subjects. Restricting dietary intake of
free fructose and/or fructans may have durable symptomatic benefits in a
high proportion of patients with functional gut disorders, but high
quality evidence is lacking. It is proposed that confusion over the
clinical relevance of fructose malabsorption may be reduced by regarding
it not as an abnormality but as a physiological process offering an
opportunity to improve functional gastrointestinal symptoms by dietary
change.
Fructose malabsorption
Dietary fructose induces abdominal symptoms in
patients with fructose malabsorption.
I am diagnosed with fructose malabsorption disorder by Dr. Satish Rao of the University of Iowa. My gastroenterologist was unable to accurately diagnose me (after 10 years and many tests) and sent me to Dr. Satish Rao. I have been doing a lot of research on the dangers of excess fructose in your body (diabetes, cancer and liver disease).
Fructose and flatulence
Increased consumption of fructose can
cause gastrointestinal distress, resulting in symptoms such as bloating,
flatulence and diarrhea. Individuals with altered gastrointestinal
function, such as inflammatory bowel disease or irritable bowel, therefore
need to limit the amount of fructose consumed. Fructose empties from the
stomach more rapidly than other sugars and is more slowly absorbed than
glucose. When foods and beverages containing fructose as the dominant
sugar are consumed, the capacity for fructose absorption in the small
intestine can easily be exceeded. A study by Beyer et al. investigated the
frequency of fructose malabsorption and gastrointestinal symptoms in
normal healthy individuals using two doses of fructose (25 and 50 g).
Fructose absorption was measured using three-hour hydrogen breath tests.
Mean peak breath hydrogen, time of peak area under curve for breath
hydrogen and gastrointestinal symptoms were measured and differences
analysed. More than half of the 15 adults showed evidence of fructose
malabsorption after 25 g and more than two-thirds after 50 g, indicating
that commonly consumed amounts of fructose may result in mild
gastrointestinal distress in normal individuals.
High fructose consumption
and liver disease
While the rise in non-alcoholic fatty liver disease parallels the increase
in obesity and diabetes, a significant increase in dietary fructose
consumption in industrialized countries has also occurred. The increased
consumption of high fructose corn syrup, primarily in the form of soft
drinks, is linked with complications of the insulin resistance syndrome.
Furthermore, the hepatic metabolism of fructose favors de novo lipogenesis
and ATP depletion. Increased fructose consumption contributes to the
development of non-alcoholic fatty liver disease.
Questions
I came across this article, can you comment on it? "Diets high in fructose - a
type of sugar found in most processed foods and beverages - could impair spatial
memory, says a study on adult rats. To reach the conclusion, Amy Ross, a
graduate student in the lab of Marise Parent, associate professor at Georgia
State’s Neuroscience Institute and Department of Psychology, fed a group of
Sprague-Dawley rats a diet where fructose represented 60 percent of calories
ingested during the day. She placed the rats in a pool of water to test their
ability to learn to find a submerged platform, which allowed them to get out of
the water. She then returned them to the pool two days later with no platform
present to see if the rats could remember to swim to the platform's location.
"What we discovered is that the fructose diet doesn’t affect their ability to
learn," Marise Parent said. "But they can’t seem to remember as well where the
platform was when you take it away. They swam more randomly than rats fed a
control diet," the expert added. "
It is not unusual to have poor brain function when the diet
is so unbalanced with any type of sugar, it is rare for most humans to consume a
diet that is so high in fructose, but those that do may not have optimal brain
function.