The Dangers of Fructose


In recent weeks I’ve heard from readers who are perplexed by an upcoming “Diabetic Ice Cream Social” where participants are invited to eat something, presumably ice cream, in order to advocate for the right of a diabetic to eat as he or she pleases. This event came to be in 2011, I’m told, after a reporter named Wendell Something suggested that giving ice cream to a diabetic is the equivalent of giving a drink to an alcoholic.


A certain stupid, idiot, alarmist, asinine, militant, Jewish, Nazi blogger (OMG, that’s me!) has publicly questioned using ice cream (even if it’s not ice cream) as a platform for diabetes advocacy.  I do not believe I have the right to tell anyone what to eat, nor do I believe I have the right to offend anyone.  I apologize to those I have offended.  I do not express my opinions out of a mean spirit, but out of genuine concern.


Now let’s so back to Mr. Something. Understandably, his alcohol analogy enraged many people with diabetes.  The irony here (and, no, I’m not defending Wendell) is that one of the world’s leading researchers and physicians, Dr. Robert Lustig Professor of Pediatrics in the Division of Endocrinology at University of California, San Francisco, and Director of the Weight Assessment for Teen and Child Health (WATCH) Program at UCSF, believes that giving ice cream to anyone, diabetic or not, is similar to giving a drink to anyone, alcoholic or not.  Why?  Because the metabolic effects and central nervous system pathways of fructose and ethanol (alcohol) are very similar.


Really?  That’s what you’re thinking right now, isn’t it?  In order to try to explain Lustig’s conclusion, I am going to pull some Lusting quotes and make an effort to summarize points from this May 2011 video, in which Lustig addresses the causes of the obesity epidemic of the last 25-30 years and what we can do to stop it.   


*This video is so worth watching. 



Curbing obesity: The first thing we have to do is ignore conventional wisdom.  Eat less, move more isn’t going to make you lose weight.  And if it does, there’s a high chance the weight will return.  Exercise is a good thing.  It keeps you healthy, but it doesn’t keep you thin.  What Lustig suggests is that changing our behavior won’t change our weight problem.  The reason is that behavior has a biochemical basis behind it. In obesity, the biochemical process has to do with a hormone called leptin.  Leptin comes from our fat cells and tells the brain that we have had enough to eat.  When leptin goes down, the brain sees starvation.  In obesity, leptin isn’t working. 


So what has changed to make leptin stop working in the last 25 years?  Something environmental? Some possibilities: Exposure to estrogens, phthalates, organo chlorines, dioxins and polychlorinated biphenyls, organotins, and/or something in our diet.


Lustig says that something is fructose.   We need to address the dangers of fructose.


Are you now thinking… WTF?  Fructose is fruit sugar and that’s natural and therefore good. Not exactly.  Fructose is the sweet part of sugar, whereas glucose is not sweet.  Glucose is the energy source for all life – every organism on earth runs on glucose.  You can find glucose in bread, potatoes, pasta, and rice.  Lustig emphasizes – it is not sweet. 

 The other ose that’s important to mention now is sucrose. Sucrose (table sugar) is 50% glucose and 50% fructose.   

 And then there’s the evil high fructose corn syrup (HFCS) we’ve all heard so much about.  HFCS is a processed sweetener derived from corn and is 42-55% fructose.  It was invented in Japan in 1966 and began to be used in America in 1975. “We’re consuming 63 pounds of HFCS a year and this is something we’ve never had in our food supply before.”

 Here’s another shocker:  According to Lustig, HFCS and sucrose are equally bad.  “They’re both poison.” 

Glucose vs Fructose: What are some of the dangers of fructose?

 Fructose is seven times more likely than glucose to cause a “browning” reaction which damages your arteries.  Fructose does not suppress gherlin, the hunger hormone that tells your brain you’re hungry.  (If a kid drinks a soda before a meal, he will eat more than if he did not have a soda.)  Acute fructose does not stimulate insulin or leptin.  If you don’t stimulate leptin, your brain thinks you’re hungry so you eat more.  And importantly, the hepatic (liver) metabolism of fructose is different. Chronic fructose exposure promotes metabolic syndrome – hyperinsulinemia, high insulin levels, insulin resistance, type 2 diabetes, obesity, hypertension, lipid problems, heart disease, fatty liver disease, polycystic ovarian disease and early data suggests cancer and dementia, as well.

 All of these diseases of energy balance, Lustig says, are a problem at the level of the liver. So keeping the liver healthy is important.

And this is where the alcohol connection comes in. You get alcohol from the fermentation of sugar – think wine. “The big difference between alcohol and sugar in terms of how your body deals with it is that for the alcohol, the yeast does the first step of metabolism, which in science is called glycolysis.

For sugar, we do our own glycolysis, but ultimately after that, the substrate, the product of that metabolism, is delivered to an area of the cell called the mitochondria. The mitochondria is the part of the cell that burns energy and creates chemical energy for your body to use.

If you overload your mitochondria, and it doesn’t matter what the substrate was that got you there, you’re going to end up having that mitochondria convert that to liver fat, and when your liver converts it to fat, it starts getting sick, and that is what we have seen.” (

How ose-s are metabolized:

 Glucose metabolism: If you take 120 calories of glucose (2 slices of bread), 96 of the calories will be metabolized by all of the organs in the body because every organ has a glucose transporter.  Twenty-four calories end up in the liver as glycogen (liver starch), a non-toxic storage form of glucose in the liver. 

 Ethanol metabolism: Ethanol is a carb, and it’s also a toxin, a regulated toxin.  Every country in the world has an alcohol policy. 

 If you take 120 calories of ethanol, a shot glass, 96 calories go to the liver.  The liver has to work four times harder than it does with glucose. 

 Sucrose metabolism: If you take 120 calories of sucrose, an 8 ounce glass of orange juice, the glucose does the same split as before, but the fructose goes entirely to the liver because the liver is the only organ which can metabolize fructose.  The result is 72 calories to the liver, or three times more than with glucose.

 [There’s an important take away message here for those of us who inject insulin: A carb is not a carb! My attitude has been that a carb is a carb – if I have to bolus for it, what difference does it make?  Apparently, I should have checked this first with my liver.  Sorry, Liver.]

 Lustig explains that our current food supply is loaded with fructose (added sugar) specifically for the food industry’s purposes, because it makes food taste better (“Add enough sugar and you can make dog poop taste good.  Your kids are eating sugar-flavored dog poop.”) and increases shelf life.  This has a toxic side effect in our livers, which drives chronic metabolic diseases.

The only thing that can reverse this constant liver toxicity is reduction in consumption of sugar.  There is no other way to treat the problem. There are no drugs for this nor will there be any.

Then what can we do?  The food industry is powerful and the federal government isn’t likely to help since we export sugar all over the world.  And let’s not forget – sugar is addictive.  Studies, both in animals and humans, show that the area of the brain, the reward center, is affected by sugar the same way it is by tobacco, alcohol, nicotine, cocaine, and heroin.

 So how do we get societal consumption of sugar to go down? (  Lustig proposes we regulate sugar like we regulate alcohol and other potentially abusive and addictive substances.  Education, like the Just Say No, campaign have failed and will fail.  Classroom education fails too, not surprising given the constant junk food marketing and advertising aimed at children.

I believe there’s something else, aside from regulation,that will work.  Peer education and peer support.  I believe we can encourage each other to skip the sugar.  I believe that there’s enough power in social media to influence the food industry and the federal government.  I don’t think we have to be doomed to an obesity epidemic or chronically sick livers. Lustig says, “Our environment has changed our biochemistry and our biochemistry has changed our behavior.  We can’t fix our behavior, but we could fix our environment.”  We have to.

For more from Dr. Lustig you can purchase this book on Amazon or pre-order Fat Chance.





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10 years ago

my take away was not “dont eat fruit” but rather watch your consumprion of sugar (especially processed and HFCS).

yes, this is not a revelation but our society is by and large ignorant to this basic idea. that is slowly changing, though. 

Padraig hogan
Padraig hogan
10 years ago

And what’s more, a “paleo” diet is full of fruit which has a very high percentage of fructose. These people calling themselves “paleo” and eating a diet low in carb are full of crap, ask the vast majority of paleoanthologists and they will tell you that primitive man before he left Africa, eat a diet very high in fruit, just like all the other great apes do to this day. 

Padraig hogan
Padraig hogan
10 years ago

“one of the world’s leading researchers and physicians” my hat. Dr. Lustig is nothing but a loud and pretentious hack. He just uses HFCS to “prove” his “theories” about fructose being the bad guy, when normal fruit causes no such damage whatsoever and people like you lap it up. So your joke idea of eating lots of ice cream and avoiding the fructose is just that, a joke. And you will remain fat (yup, I went there) like all his other “fans”, until you start facing facts and eating normal, unprocessed foods like fruit. 

Nathan Shackelford
10 years ago

Yes, the diabetes community needs to hear the same news that the progressive health conscious people around the world (Paleo/Primal/ketogenic/Protein Power) already accept. A carb is not a carb. A calorie is not a calorie. I’ve experimented on myself plenty to prove it to myself. Great info.

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