Fructose1 – T2D 27

posted in: Diabetes, Health and Nutrition | 46

The Deadly Effects of Fructose

In 2009, Dr. Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco delivered a ninety minute lecture entitled “Sugar: The Bitter Truth”. It was posted on YouTube as part of the university’s medical education series. Then a funny thing happened. It went viral.

It was not a humorous cat video. It was not a video of a toddler throwing a baseball into Dad’s groin. It was a nutrition lecture filled with biochemistry and complicated graphs. But there was something about this particular lecture that grabbed the world’s attention and refused to let go. It has now been viewed more than six million times. What was this attention-grabbing message? Sugar is toxic.

Sucrose, against all logic and common sense, had not always been considered unhealthy. The U.S. Food and Drug Administration undertook a comprehensive review in 1986, eventually declaring “there is no conclusive evidence on sugars that demonstrates a hazard.” Even as recently as 2014, the American Diabetes Association website stated “experts agree that you can substitute small amounts of sugar for other carbohydrate-containing foods into your meal plan.”

The tide began to turn in 2004 when Dr. George Bray from the Pennington Biomedical Research Center of Louisiana State University showed that the increase in obesity closely mirrored the increased use of high-fructose corn syrup in the American diet. In the public consciousness, high-fructose corn syrup developed as a major health issue. Others correctly pointed out that high-fructose corn syrup use increased in proportion to the decreased use of sucrose. The rise in obesity really mirrored the increase in total fructose consumption, whether the fructose came from sucrose or from corn syrup.

Dr. Lustig was not the first physician to warn about the dangers of eating too much sugar. In 1957, prominent British nutritionist Dr. John Yudkin warned anybody who would listen about the danger. Faced with the growing incidence of heart disease, Yudkin recognized that sugar likely played a prominent role. However, the world instead chose to follow Dr. Ancel Key’s condemnation of dietary fat instead. Sugar’s main danger, other than the increased calories, was dental cavities. After leaving academic medicine, Yudkin wrote an eerily prescient book entitled “Pure, White and Deadly”, but his warnings have largely been unheeded.

The 1977 Dietary Guidelines for Americans distinctly warned the general public about the dangers of excessive dietary sugar, but this message got lost in the anti-fat hysteria that followed. Dietary fat was public enemy number one, and concerns about excess sugar faded like the last rays of sunset. Sugar consumption rose steadily from 1977 to 2000, paralleled by the rising obesity rates. Ten years later, type 2 diabetes followed doggedly like a bratty little brother.

Obesity alone, however cannot explain the entire upsurge in diabetes. Many obese people have no evidence of insulin resistance, diabetes or metabolic syndrome. On the other hand, there are also the skinny type 2 diabetics. This is obvious on a national level, too. Some countries with low obesity rates have high diabetes rates while the opposite is true, too. Sri Lanka’s obesity rates have remained at 0.1% from year 2000 – 2010 while diabetes rose from 3% to 11%. Meanwhile, over the same time period, in New Zealand, obesity rose from 23% to 34% while diabetes fell from 8% to 5%. Sugar consumption may well explain much of this discrepancy.

What was it specifically about sugar that makes it particularly toxic? It isn’t simply that sugar is a highly refined carbohydrate. The Chinese diet of the early 1990s, as documented by the INTERMAP study, was based primarily upon white rice and therefore very high in refined carbohydrates. This presents an apparent paradox, since they suffered little obesity or type 2 diabetes.

One crucial point is that the 1990s Chinese diet was extremely low in sugar. Most refined carbohydrates such as white rice, are composed of long chains of glucose, whereas table sugar contains equal parts glucose and fructose. As Chinese sugar consumption started to increase in the late 1990s, diabetes rates moved in lockstep. Combined with their original high carbohydrate intake, this is a recipe for the diabetes disaster.

To a lesser extent, the same story played out in the United States as well. Carbohydrate consumption gradually switched from grains to sugar in the form of corn syrup. This paralleled the rising incidence of type 2 diabetes.

When data from over 175 nations is reviewed, sugar intake is intricately linked to diabetes even independent of obesity. For example, Asian sugar consumption is rising at almost 5 percent per year, even as it has stabilized or fallen in North America. The result has been a made-in-China tsunami of diabetes. In 2013, an estimated 11.6 percent of Chinese adults have type 2 diabetes, eclipsing even the long-time champion: the U.S., at 11.3 percent. Since 2007, 22 million Chinese were newly diagnosed with diabetes—a number close to the population of Australia.

Things are even more shocking when you consider that only 1 percent of Chinese had type 2 diabetes in 1980. In a single generation, the diabetes rate rose by a horrifying 1160 percent. Sugar, more than any other refined carbohydrate, seems to be particularly fattening and leads specifically to type 2 diabetes. Yet the Chinese were being diagnosed with diabetes with an average body mass index of only 23.7, which is considered in the ideal range. By contrast, American diabetics averaged a BMI of 28.7, well within the overweight category.

The prevalence of diabetes climbs 1.1 percent for every extra 150 calories per person per day of sugar. No other food group showed any significant relationship to diabetes. Diabetes only correlates with sugar, not other sources of calories.

Similar data can be found for sugar-sweetened beverages, one of the largest sources of sugar in the American diet. Between the late 1970s and 2006, the per capita intake of SSBs almost doubled to 141.7 kcal/day. Each additional 12-oz serving of SSB increases the risk of diabetes by 25%. Risk of metabolic syndrome is increased by 20%.

High fructose corn syrup consumption, chemically almost identical to sugar also shows a tight correlation to diabetes. Countries using large amounts of HFCS suffered a twenty percent increased prevalence of diabetes compared to those that did not. The United States, by the way is the undisputed heavyweight champion of HFCS with a per capita consumption of almost 55 pounds.

What distinguishes sugar from other carbohydrates? What is the common link to disease? Fructose.

Fructose

Paracelsus (1493-1541), the Swiss-German physician considered the founder of modern toxicology neatly summarized one of its most basic principles as “The dose makes the poison”. Anything, even if typically consider beneficial, can be harmful in excessive amounts. Oxygen can be toxic at high levels. Water can be toxic at high levels. Fructose is no different.

Natural fruit consumption contributes only small amounts of fructose to our diet, in the range of 15 to 20 grams per day before the year 1900. By World War II, the increased availability of sugar allowed yearly per capita consumption of 24 g/day. It rose steadily to 37 g/day by 1977.

The development of high-fructose corn syrup allowed fructose intake to skyrocket to 55 g/day in 1994 accounting for 10% of calories. Consumption peaked in the year 2000 at 9 percent of total calories. Within the space of 100 years, fructose consumption had increased by five fold. Adolescents in particular were heavy users of fructose often eating as much as 25% of their calories as added sugars at 72.8 grams/day. Currently, it is estimated that Americans eat 156 pounds of fructose-based sweeteners per year. The dose makes the poison.

High-fructose corn syrup was developed in the 1960s as a liquid-sugar equivalent of sucrose. Sucrose was processed from sugar cane and sugar beets. While not exactly expensive, it wasn’t exactly cheap. High-fructose corn syrup, however, could be processed from the river of cheap corn that was flowing out of the American Midwest—and that was the decisive factor in favor of high-fructose corn syrup. It was cheap.

Soon, high-fructose corn syrup found its way into almost every processed food imaginable. Pizza sauce, soups, breads, cookies, cakes, ketchup, sauces—you name it, it probably contained high-fructose corn syrup. It was cheap, and big food companies cared about that more than anything else in the world. They raced to use high-fructose corn syrup at every opportunity, often replacing sucrose due to its cost advantage.

Sugar basics

Glucose is the main sugar that is found in the blood. The terms “blood sugar” and “blood glucose” are used interchangeably. Glucose can be used by virtually every cell in the body, and circulates freely throughout the body. In the brain, it is the preferred energy source. Muscle cells will greedily import glucose from the blood for a quick energy boost. Certain cells, such as red blood cells, can only use glucose for energy. Glucose can be stored in the body in various forms, such as glycogen in the liver. If glucose stores run low, the liver can make new glucose via the gluconeogenesis process.

Fructose is the sugar found naturally in fruit and the sweetest tasting naturally occurring carbohydrate. Only the liver can metabolize fructose and it does not circulate freely in the blood. The brain, muscles and most other tissues cannot use fructose directly. Eating fructose does not appreciably change the blood glucose level, since they are different sugar molecules.

Table sugar, known as sucrose, is composed of one molecule of glucose linked to one molecule of fructose, making it fifty percent glucose and fifty percent fructose. Chemically, high-fructose corn syrup is composed of fifty-five percent fructose and forty-five percent glucose. Pure fructose is generally not consumed directly, although is can be found as an ingredient in some processed foods.

Carbohydrates are single sugars or chains of sugars all linked together. Glucose and fructose are examples of single sugar carbohydrates. Sucrose is a two-chain carbohydrate since it contains one molecule each of glucose and fructose.

Starches, the main carbohydrate in potatoes, wheat, corn and rice, are long chains of glucose. Produced by plants, starch functions mostly as a store of energy. Sometimes they are stored underground, as in root vegetables, and other times above ground as in corn and wheat. By weight, starch is approximately 70% amylopectin and 30% amylose. Animals, including humans, link glucose together in chains for storage in the form of glycogen instead.

Once eaten, the chains of glucose in starches are rapidly broken down into individual glucose molecules and absorbed into the intestines. The Glycemic Index measures the blood glucose raising ability of various carbohydrates. Pure glucose will obviously cause the largest rise in blood glucose and is therefore given the maximal value of 100. All other foods are measured against this yardstick. Bread, made predominantly of white flour also has an extremely high glycemic index since the refined starch from wheat is quickly digested into glucose.

Other dietary sugars, like fructose or lactose (the sugar found in milk) do not raise blood glucose levels appreciably, and therefore have correspondingly low glycemic index values. Since sucrose is half glucose and half fructose, it has an intermediate glycemic index. Only the glucose portion of sucrose raises blood glucose appreciably.

Fructose, which neither raises blood glucose nor insulin was considered more benign than other sweeteners for many years. An all-natural sweetener found in fruit that didn’t raise the Glycemic Index sure sounded healthy. But it had a hidden dark side, one that was not obvious for many decades.

The toxicity of fructose could not be seen by looking at the blood sugars, only by looking at the slow accumulation of fat in the liver. The key was the fatty liver.

46 Responses

  1. sten bjorsell

    Great Post again! You rightfully gave Robert Lustig great credit for his lecture. I was astounded when it came out, with just some 10,000 youtube views in 2009. Did my little bits to spread this important information. Last time I checked it was 3 million views and good to see it has doubled again! If both your blog and Lustig’s lecture can be picked up in China we may soon see a further 10 folding!

    Summary: Fructose -> Fatty Liver -> Metabolic syndrome -> (Diabetes-2) -> Heart disease. Being “fat” or not! According to doctor Joseph R. Kraft, most heart disease involves undiagnosed diabetes-2, the reason for my brackets (Diabetes-2). Looking forward to you exploring this and other consequences of fatty liver and metabolic syndrome in future posts now when we know the origins better.

  2. Rajesh Pankaj

    Bravo Dr. Fung

    Once again you hit the bulls eye. If Fructose is equally responsible for T2D (even in lean diabetics like me), what should we eat. Technically everything is sugar, whether its Fructose or Sucrose. One hit you from from while other kicks your A**.

    • Is there not a difference in eating fruit which has natural fiber vs eating processed fructose/sugar? I think the big issue is everything is processed

      • Yes, kind of. With processing, yes, you can eat much much more fructose than was possible before.

        But because fruit is much more available, it is now possible to overeat on it where most Americans wouldn’t have had this option prior to 1900. Source: people get fat eating fruitarian diets.

  3. Stefan Constantinescu

    So how much fruit can one consume?

    I mean, I love a green apple, and bananas make my oatmeal taste even better than it already does.

    • I think it’s most likely individual, and can vary over time. I’ve personally ruined by body by eating a high carb, low fat diet for decades. If I eat fruit (even so-called low glycemic index fruit like grapefruit), I get high blood sugar and feel terrible. I still eat fruit at times, typically berries in season. Otherwise, I avoid fruit. I have no fruit at all for months out of the year.

      There are definitely people who don’t seem to be affected by it, though. For instance, you mention oatmeal. That’s another product that makes my blood sugar go through the roof (not to mention that oatmeal, with or without fruit, is not filling for me — I’ll be hungry 15 minutes after eating, which is likely an insulin response).

      If you can eat oatmeal with no problems, then some fruit won’t be bad.

      • Have you listened to Jason Fung on YouTube about fasting and keto diet for diabetics? Very interesting. According to him diabetes 2 is totally reversible.

    • Kresser’s book says a few pieces a day is okay. I believe the Jaminets of the Perfect Health Diet recommend a 5:1 glucose to fructose ratio.

  4. Sometimes a little knowledge can be hazardous to your health. I remember so well back in the 1970s or 1980s, when we learned that pure fructose didn’t raise blood glucose, we hurried to the health food store to buy bags of the stuff to use in place of regular sugar. We thought we’d found a natural sweetener with no bad side effects. Big mistake!

  5. Does this mean we should avoid fruit / what would be an acceptable amount to eat. I’ve switched from the “hard stuff” e.g. chocolate to fruit as a replacement which is obviously better albeit not perfect. Are we just trying to keep total fructose consumption under x g/day or would not having any be optimal. Ideally I want something that satisfies my sweet tooth whilst not screwing over my body – it seems hard to find.

    • Have you looked at the low carb, high fat way of eating? The fat is very satisfying and I find I don’t crave sweet food when I eat this way. A maximum of 2 fruits a day seems to be the General recommendaton

    • Take a look at the Diet Doctor website under what to eat. The website lists 3 options to choose from–Strict Low Carb; Moderate Low Carb and Liberal Low Carb. It is a good way to test what your body responds to best.

  6. ON Fructose, it is much worse than the article above states:
    I was hoping that Dr. Fung was more aware of the work of Dr. Robert Lustig. His technical work is at http://advances.nutrition.org/content/4/2/226.full Fructose: It’s alcohol without the Buzz. In his book chapter 11, Fat Chance, he explains that fructose: 1) 7 times more reactive than the sugar glucose; 2) that glycation is the random bonding of a sugar to a protein (certain amino acids); 3) that when bonded to the protein it adversely affects the protein’s function. 4) that there is a cellular method for clearance of glycation; 5) that Lustig estimates that at over 40 gm daily that system is over whelmed. 6) 100% is metabolized in the liver; 7) that when eaten with starches (glucose) is metabolized in the liver after glucose; 8) that like ethanol, fructose is toxic to the liver. If you are looking for a starting point for insulin resistance, fatty liver, and much worse, the big one is fructose. .
    For more on its health consequence a start is at https://en.wikipedia.org/wiki/Advanced_glycation_end-product
    Among the articles I posted is one by the Harvard Heart Letter Abundance of fructose not good for the liver, heart. http://healthfully.org/dja/id5.html

    • Look at the title. This is part 1 of a series. With all due respect, don’t assume this comprises Dr. Fung’s total familiarity with the literature on fructose, for Pete’s sake.

  7. Roger Bird

    Yesterday I rebounded for 30 minutes while breathing 95% pure oxygen. I do this every day. For 2 months I breathed 95% pure oxygen while working out on an elliptical. I lowered my resting heart rate from 54 to 49. I felt great. I want to do this again today. What this is called is EWOT, or Exercise With Oxygen Training (or Therapy). If I could get 100% oxygen, I would.

    I am not going to stop admiring and respecting Jason just because of this. No one is perfect. Jason has the most perfect grasp of the ins and outs of diabetes. He just doesn’t know about EWOT.

    • Christine S.

      Roger Bird, what does this have to do with a post on fructose? If and when Dr. Fung does a post on EWOT I’m sure he’ll welcome comments. However, since EWOT has nothing to do with obesity or diabetes, I suspect this will never happen. Have a nice day.

      • Rajesh Pankaj

        Christine, He was just making his point as, at one place in this Blog, Dr Fung mentions that Oxygen could be toxic at high levels.

        • Roger Bird

          Exactly. And, of course, it gives me an opportunity to spread the word about EWOT. (:->) It has been said that EWOT can probably improve any health condition imaginable. I do not doubt that for a second.

        • TJtheGrouch

          FYI: premature babies subject to high concentrations of oxygen become blind.

          • Roger Bird

            It’s true. I have met a grown-up person who was such a baby. And she was not all that crazy about the medical profession. But the Medical Deities also put babies in bright lights, and any moron can figure out that that isn’t a good idea. With our two babies, we did not let that happen. It was very easy to drape a towel between the light and my children’s faces. Neither difficult nor rocket sciencey.

  8. sten bjorsell

    Regarding fruit, hold off a little before you worry! It is mainly the added sugar in sodas and low-fat processed foods that are the culprits, but fruit can be bad too!
    A recent Swedish study clearly showed different health outcomes in terms of heart disease when fruit & vegetables (f&v) were eaten, depending on the amounts of fat consumed !

    The study ran for 12 years with 1752 men; end point: hospitalizations plus deaths in heart disease, called ‘events’ below.
    High-fat: Dairy-fat as full-fat milk, cream, and butter. Low-fat: modern low-fat products and vegetable oils.

    In the groups that did not eat f&v daily, the high-fat group had 8% events and the low-fat group 10% events over the 12 years. An insignificant difference in favor of high fat.

    With f&g, however, (unexpected) huge differences were seen, in opposite directions!
    Events were then found to go from 8% to 13.3% in the low-fat group and from 10% to 3.1% in the high-fat group.
    That is 60% more events with f&v in the low-fat diet while events are 70% reduced with f&v in the high-fat group!
    Comparing end outcomes, over 400% more disease with f&v in the low-fat group than in the high-fat group!

    So why did f&v make people sicker on a low-fat diet but healthier on a high-fat diet?

    Most micronutrients and antioxidants are fat soluble which means that much of it is bound to get lost, expensive urine, with too little fat to absorb them on a low-fat diet.

    The f&v did damage one way or another on the low-fat diet, seen from 30% higher disease rate, and fructose is a prime suspect. Same potential damage was protected for by absorbed good stuff in the high-fat group. (70% lowered disease rate)

    Finally, there are neither fat nor antioxidants in sodas and not much if any in modern low-fat processed food, likely making both substantial health risks when consumed often.
    Full-text study link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2790097/

  9. Ron Hunter

    So Doc – how good are imaging techniques to diagnose fatty liver? Do you just assume it when someone has metabolic markers and bad liver enzymes? I suppose a punch biopsy would be the best but who wants to go through that?

    • Ron, it shows up well. Take a look at the attached talk by Dr Michael Mosley at 16.17 he shows a scan of his own visceral fat. The sort created by fructose and sugar. The good news is that it’s the first fat your body uses and loses when eating a LCHF type diet.

      Dr Mosley is a BBC science producer and advocate of the 5:2 pattern of fasting. I don’t agree with everything he says, but mostly I do and he’s become a useful voice.

      https://www.youtube.com/watch?v=6d-LMzIlr5I

  10. Judy Clauss

    I am a Latent Autoimmune Diabetic, (diagnosed as an adult0, and wonder if it is safe and or beneficial for this category of diabetics?

  11. Fructose is indeed more benign then glucose, by a good margin. We certainly consume way too much sugar, sucrose, and in this case the dose does make the poison, although starches do us in even more, including whole grains, which not only are ultimately digested and contribute to glycemic load, they are even higher in toxins like lectins.

    The damning evidence against fructose is actually based upon junk science, you need to control for all variables and in this case they gave people an excess of calories by having them drink a bunch of extra cokes and not surprisingly this contributed to liver fat. Ray Peat has some great discussions on this to serve to balance out Dr. Lustig’s fanaticism against glucose, and straighten us out as well.

    High fructose corn syrup though is bad news, even Dr, Peat can’t argue against that, although he does feel that diabetics are fructose deficient, an idea that even I found crazy at first but he does present some pretty good evidence.

    The real problem with sucrose is that one does not achieve satiety like you do with normal foods, and thus the junk food junkies can go crazy with this, as they so often do. I do think though that sucrose is healthier for us than grains, gram for gram, as sucrose is only half glucose where grains are converted to pure glucose, and this is where the glycemic model has some sway.

    The worst upshoot of people like Lustig is they have people focusing on sugar so much when we should be focused on excesses of carbohydrate consumption, and this is the epidemic we need to be worried about, including sugar and all other forms of carbs. We also have been lulled into a false sense of security with going with whole grains and this stuff is just plain bad for us in excess.

    The dose does always make the poison though 🙂

    • “Dr. Lustig’s fanaticism against glucose”
      You lost me here right around here.

      • “Fructose is indeed more benign then glucose, by a good margin.”

        What is your theory here? Because it doesn’t raise BG and is shunted off into the cells instead, including the liver? WHY do you think fructose is so benign?

        It isn’t an accident that Dr. Fung placed this post immediately after his last post “Insulin resistance protects against…insulin! T2D 26”: they’re related. The point is it isn’t only excess food energy in the blood that’s a problem, it’s also when it’s excessive on a chronic basis in the cells. That’s what he’s getting at here.

        Yes, fructose doesn’t raise blood glucose much. No, that doesn’t mean it’s benign: quite the opposite.

    • Roger Bird

      Anyone who uses the phrase “junk science” is automatically dismissed around here. I did not get past that phrase.

    • Mike Ellwood

      @Ken Stephens:

      Richard (“The other”) Feinman (Richard David Feinman) also dissents from Lustig’s views on Fructose. He takes them apart quite comprehensively in at least one of his blog articles. And Feinman is probably much better qualified in this field than Lustig is.

      (I also find a lot of Ray Peat’s views very interesting. His views on sugar generally are controversial, to say the least).

      One thing I don’t get about Lustig’s argument is that if fructose is so evil, why is it ok in fruit? He claims that the fibre is enough to slow down absorption so it’s not a problem. I don’t buy this. I used to be able to demolish a pound of sweet grapes in one very short sitting (and then be looking for more grapes). There may be fibre, but it’s mostly sweet liquid, and I’ll bet it’s absorbed pretty fast. And (sorry Dr Fung), it _is_ possible to become addicted to sweet fruit, (contrary to what you write in “The Obesity Code”): Reader, I was that addict.

      The sad fact is that for many of us, struggling with weight and insulin resistance, sweet fruit is a guilty sin that just has to be avoided. (Obviously does not apply to everyone, of course). It should also be said that the sugar in fruit is not all fructose of course, but a variable mixture of fructose, glucose, and sucrose. Arguing which is worst: glucose, fructose, or sucrose, seems moot. For some people at least, they all should be severely restricted.

      • Mike, I also find the argument over which is wrose – fructose or sucrose – a bit academic, although the point about fructose making visceral fat is important. I avoid both as much as possible.

        I’m careful with fruit because modern fruit is so much sweeter than its ancestors and is available all year around, but I eat rasperies and other berries in smallish quantities. Grapes are very high in sugar and I see why they can fly down. Sven’s basic point about soda and sugar-laden junk being the main problem is surely right.

  12. I’m a bit confused here as I read above, “Eating fructose does not appreciably change the blood glucose level, since they are different sugar molecules.”

    Nearly 3 1/2 years ago I wanted to improve my overall health, lose weight, lower FBG and A1c and decrease my symptoms of CAD which I already have. I started a transition from a high carb diet to a very low one, increasing healthy fat and ultimately trying to switch body fuel from glucose to ketones, or dietary ketosis. It took me me nearly 3 months of eating <30g carbs a day to become fully "keto adapted". I've been an avid hiker for 20 years and at the high range of healthy BMI. I did develop a blocked coronary artery which was stented 12 years ago.

    Before becoming fully keto adapted, even though in dietary ketosis, under extreme energy demands for a long time, such as continuous hiking or climbing up steep mountains, I would experience low blood sugar. I'd feel shaky, energy depleted, light headed and the need to eat, preferably something high carb. Once my BG dropped into the 40 range and I thought I was going to pass out. I sat on a ledge and ate some raisins and a banana and felt better in a few minutes. My BG did in fact go up. I did carry a tester and checked BG often while hiking. Was it coincidence that my BG stabilized and increased after the fructose I ate, or is there other BG increasing sugars in fruit?

    After becoming fully keto adapted, I can hike for hours, even all day, expend tremendous energy and my BG will remain flat. I will momentarily tire, may need a rest for a minute or two, but recover quickly and do not need food. I may generally take bacon, almonds, sardines. My partners have to stop every couple of hours for energy bars and sugar to keep them going. So now, I'm 6', 162 lbs. 67 yo with the energy of a 30 yo or better, A1c 5.6, no signs of CAD.

    • Fruit is about half glucose, or a bit more, as far as the sugars go, and contains varying amounts of starches and fibers.

      For that matter, the fructose is processed in the liver and ~25-50% of that is eventually converted to glucose under normal conditions.

  13. Mike Ellwood

    By the way, this point about fructose being as toxic to the liver as alcohol is another of Lustig’s “facts” that Feinman disputes.

    And it seems unlikely, because studies like this:

    https://www.ncbi.nlm.nih.gov/pubmed/1854373

    …show that fructose actually speeds up the metabolism of alcohol. I don’t see how it could do that if it was also poisoning the liver.

    • maybe they induce metabolism by inducing the same enzymes in the genome ? because they are metabolised the same way? did not occur to you?

  14. Word “fruit” sounds natural and healthy so (almost) no one dare say nothing against them. Anyhow todays fruits aren’t the same as what they were when we were cavemen. Today even apes in zoos have become diabetic by eating too much fruits.

    • Quantity matters. The bear survives the winter with that big fat that it has acquired. How did it do that? Bears eat berries all the time. It makes perfect sense – they eat berries, they become insulin resistant, in the prolonged period of hyperinsulinemia they put everything to fat and then fast for the winter and burns off all energy and insulin resistance becomes normal again.

    • Where did you pick up this hoary tale, JR62? Sure, many of our fruits are bigger, but they’re not sweeter.

      • Trust me—aboriginals gorged themselves on fruit whenever and wherever they could.

        Honey too.

      • Actually fruit in the US has been cultivated to be bigger, juicier, and more sugary. It isn’t what aboriginals ate. And, it is also now available year-round which would have not been the case in most locations in a far off time. The fruit and the eating patterns have drastically changed.

        • “Actually fruit in the US has been cultivated to be bigger, juicier [huh?], and more sugary [!].”

          With respect, you are wrong.

          http://donmatesz.blogspot.com/2010/03/paleo-basics-how-much-sugar-in-wild.html

          • With respect, It isn’t true that modern fruits are significantly sweeter than wild fruits.

            Blackberries, salmon berries, thimble berries? (Going by my local environment.)

            Yes, they’re SMALLER — but less sweet than, say, an apple?

            Not true.

            I’d like you to point to a study where modern fruit is sweeter than natural fruit.

            Anyway, the point being I’ve tasted many varieties of both wild and cultivated fruits—as a teenager, I lived of the land alone for three months using a food guide of what the British Columbia coastal natives ate.

            And I remember some delicious sweet fruit. Lots of it at times too, since the natives would of course gorge on it in season when they came across a source (and/or mix it with other items to create pemmican, etc.). After all—they have to eat it before the bears do!

            I’ve eaten many store bought fruit that while good, were nowhere near as sweet.

  15. I saw a lecture (you tube; Low Carb Down Under, if I remember correct), where was proposed an interesting theory:

    Fructose is meant to act as a switch to turn animals fat (metabolic syndrome) in late summer. Fat storage is needed to survive long winter. When spring came, they were lean again. Maybe people who didn’t have this quality died during Ice Age winters and now we (almost) all have this feature.

  16. Dr Fung comments that glucose is the brain’s favoured fuel. I’ve read several times that the brain prefers ketones. Any views or clarification?

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