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Fructose, insulin resistance, and metabolic dyslipidemia
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The PDF isn't that long.
This isn't junk science like anthropogenic global warming. It isn't any calorie from glucose is the same as a calorie from fructose. Fructose metabolism favors the production of triglycerides. The 2nd link explains fructose metabolism if you can deal with some biochemistry.
P.S. Non alcoholic fatty liver disease was unknown as a common diagnosis before the introduction of HFCS.
P.P.S. Before this latest paper mentioning the possible variations in actual fructose content of HFCS-55, it was claimed to be 55 % fructose, 42 % glucose and 3 % other sugars. That's almost 4:3 ratio of fructose to glucose, aka dextrose.
Pancreatic Cancers Use Fructose, Common in a Western Diet, to Fuel GrowthI read food labels and avoid junk food containing HFCS.
Is high-fructose corn syrup worse for our health than common table sugar? I’ve spent a lot of time researching this question.
First, consider how the two differ.
On the one hand, we have table sugar. Table sugar is sucrose. Sucrose is a disaccharide that consists of two larger molecules that are bonded together: a fructose molecule and a glucose molecule. If you look up the chemical diagrams of their common forms, you’ll see the fructose molecule has 5 atoms in a ring, while the glucose has 6.
To make table sugar, the sucrose from beets or cane basically is squeezed out of the plants and then purified.
During digestion inside our bodies, that glycosidic bond between the glucose and fructose molecules is very quickly hydrolyzed by digestive enzymes (like sucrase), converting the sucrose molecule into separate fructose and glucose molecules.
On the other hand, there’s high-fructose corn syrup (HFCS). HFCS is heavily processed using several enzymes to turn cornstarch first into glucose and then partially into fructose. In HFCS, the glucose and fructose molecules are chemically separate, not bonded together.
The molecular mixture of the form of HFCS common in the USA is approximately 55% fructose and 42% glucose. Sucrose, being a disaccaride, is exactly 50% fructose and 50% glucose. (For comparison, the composition of honey lies somewhere between these two ratios.)
So it’s clear that there is not a huge difference between the relative quantities of fructose and glucose in HFCS vis-a-vis sucrose. The proportion of fructose to glucose in HFCS is basically the same as in table sugar. Both sweeteners contain the same number of calories (4 kcal/gram).
Now, consider some differences between fructose and glucose.
Both molecules are natural sugar compounds found commonly in plants, but there are many biological differences resulting from the chemical differences between fructose and glucose. It turns out that fructose is sweeter than glucose. The 5-ring form of fructose fits more easily into the sweetness receptors on your tongue’s taste buds than the 6-ring form of glucose. So your brain thinks fructose tastes sweeter. On the Relative Sweetness Scale (where sucrose scores 100 by fiat), pure fructose scores 140, while pure glucose scores about 80.
Another biological difference is in how the two substances must be digested by the body. The metabolism of fructose is very similar to that of ethyl alcohol (which is just fermented sugar after all) in alcoholic beverages. Both fructose and ethanol must be processed by the liver before the cells of the rest of the body can make use of it. Through a complex chain of metabolic steps, fructose is eventually metabolized in the liver into glucose (glycogen) and fat. Glucose, on the other hand, is the ubiquitous biological fuel readily and directly usable by almost every cell in the body.
On account of the more complex hepatic pathway fructose must take for digestion, high fructose consumption can have a big impact on the liver, causing problems such as fatty liver disease, which is similar to cirrhosis of the liver caused by excessive alcohol consumption. In medical studies fatty liver disease is increasingly being linked with insulin resistance, type-2 diabetes, obesity, dyslipidemia, and high blood pressure.
As with alcohol, fructose increases blood pressure. Fructose reduces the production of nitric oxide within blood vessels, making it difficult for the vessels to relax and dilate. It also raises uric acid in the blood, which shrinks blood vessels. The effect is higher blood pressure on both counts.
Recent studies also show that consuming glucose triggers increases in a ‘satiety hormone’ called leptin that signals to the brain that we’ve eaten enough. It also blunts the effects of ghrelin, a ‘hunger hormone’ that makes us want to eat more. Fructose does not trigger these same ‘fullness’ cues. Fructose actually appears to increase our appetite.
A 2008 study found a substantial risk of gout associated with the consumption of fructose-rich foods.
The differences in metabolism of fructose and glucose have led some leading endocrinologists to call fructose a “dose-dependent toxin,” in the same way ethyl alcohol is. Fructose and alcohol are very similar in regard to disease and the metabolic havoc they wreak when consumed at a rate over 25 grams/day.
Now return to the HFCS/sucrose comparison.
The process of making HFCS is very cheap. It is even cheaper than making refined sucrose, due to government-regulated production quotas on domestic sugar, a 1977 import tariff on foreign sugar, and the subsidization of corn production.
On account of its greater sweetness and lower cost, the use of HFCS as an added sweetener has exploded in the USA: sodas, fruit juices, breads, cereals, breakfast bars, lunch meats, sauces, soups, yogurt, condiments, and many other processed foods are loaded with HFCS. The number of sugar calories Americans get today from food has increased 50% from the 1970s, due to the ubiquity of HFCS sweetening.
The HFCS lobby (Corn Refiners Association) says that HFCS is basically no different than table sugar. Both sucrose (50% fructose, 50% glucose) and HFCS (55% fructose, 42% glucose) contain a similar ratios of fructose to glucose.
They are probably basically right. The amount of fructose in HFCS is only marginally greater in HFCS compared to sucrose. It’s hard to believe the small difference could result in a large effect. But whether unfounded or not, there is a growing backlash against HFCS.
For most of human history refined sugars did not exist apart from the fairly rare consumption of honey. Before the 18th century refined sugar was an expensive luxury item. It became more widely popular in 18th century, and then in the 19th century it became a staple. After George McGovern’s 1977 Senate Select Committee on Nutrition issued a set of nutritional guidelines recommending that Americans consume less dietary fat, HFCS exploded on the scene as a low-fat substitute.
So, again, is high-fructose corn syrup worse for our health than common table sugar? It’s probably no worse. The point is that both are bad in large enough quantities, when fructose consumption exceeds around 25 grams/day, which is far less than the typical daily consumption in the standard American diet.
For more depth I highly recommend this popular video by Dr. Robert Lustig, an endocrinologist who specializes in pediatric obesity:
“Sugar: The Bitter Truth” http://www.youtube.com/watch?v=dBnniua6-oM
I’ve known this for a long time.
Taubes on Why We Get Fat
http://www.econtalk.org/archives/2012/07/taubes_on_why_w.html
Taubes on Fat, Sugar and Scientific Discovery
http://www.econtalk.org/archives/2011/11/taubes_on_fat_s.html
Both great discussions are worth a listen. It’s an hour long program and you can download it. It makes the commute bearable.