Robert Lustigs' talk pissed me off the other day. I kept having flashbacks to him saying that fructose is basically "ethanol without the buzz." And then I read someone on this site saying, "My personal opinion is that there is no obesity without sugar. There's weight gain, but not obesity." And that made me even pissier.
I think we can all agree that drinking five Big-gulps a day is a no, no. Don't do that. You're probably going to hurt yourself. No one is saying that there isn't an upper limit on fructose. It's a dose dependent hepatoxin. Ethanol is also. But if you moderately consume ethanol, you're a-okay. The question is what is moderate sugar intake. What is too much?
Alan Aragon had a blog post a while back about Lustig's fructose alarmism. Here's the gist of it:
For the specifics go here:
"There are no sacred cows" - Robb Wolf
I think it should be added that we shouldn't worship our hatred for our assumed enemies. I think that's what Lalonde's talk was about.
What says you?
Some notes from Feinmen on fructose (thanks Meredith for showing me this):
"Lustig says “ethanol is a carbohydrate.” Ethanol is not a carbohydrate. A horse is not a dog. If you said that ethanol is a carbohydrate in sophomore Organic Chemistry, you would get it wrong. Period. No partial credit."
Lustig uses the biochemistry in a misleading manner. "There is very little chemical sense in saying that ethanol and fructose are processed biologically in similar ways." "Metabolism is not static and has evolved to deal with changing conditions of diet and environment. A metabolic chart, like any map only tells you where you can go, not whether you go there." "Lustig's pathway does not show glycogen storage."
Fructose is not a toxin, is expected in the body and glucose can tautomerizes into fructose. "It is a normal metabolite. If nothing else, your body makes a certain amount of fructose. Fructose, not music (the food of love), is the preferred fuel of sperm cells. Fructose formed in the eye can be a risk but its cause is generally very high glucose. Fructose is a carbohydrate and is metabolized in ways similar to, if different in detail, from glucose but the two are interconvertible — that is why the glycemic index of fructose is 20 and not zero."
He maintains that any problem with fructose is probably a problem with glucose. I disagree.
one more day for the bounty.
Aragon says fructose is just dandy up to 100g a day. Ingest that much and report back with your TGs.
NHANES doesn't tell you how much fructose the obese consume, it gives some mean or median.
It's not the fructose that's bad, it's the uric acid that arises as a result of its metabolism. Because of their overlapping antioxidant duties, the consumption of ascorbate leads to urate excretion. In a state of nature, hyperuricemia does not occur unless there's some kind of ridiculous honey bounty that someone gorges on for a while, but that would be rare. During the course of our evolution, most of the fructose we got was from fruit and most of that fruit was packaged with vitamin C. The fruit we eat now is usually grown a distance away and shipped, which negatively impacts the amount of rapidly-degrading vitamin C. If you're eating all of your fruit freshly picked and choosing fruit that has a favorable ratio of vitamin C: fructose, then there is no risk. If you are drinking soda, it is not the same.
I advocate that people either decrease fructose consumption, increase ascorbate intake (without a commensurate increase in fructose intake) or both. I don't see why people buck against what can only be considered to be sound advice, given that most of the negative effects of fructose intake are ultimately the result of hyperuricemia.
Lustig mentions that fructose is packaged in nature with fiber, with attentuates its absorption, but I doubt that has much effect at all on serum uric acid levels. There are some fruits, such as bananas that have so much fructose and so little vitamin C that they become very potent uric acid generators. If you must eat them, you ought to supplement with vitamin C.
I did some digging after our last exchange in order to find some more info about the mechanisms by which, and under what circumstances, fructose becomes dangerous. There appear to be three major potential problems with it: hyperleptinemia, hyperuricemia (and hyperinsulinemia as a result).
The former occurs as a result of heavy and prolonged fructose intake, which raises VLDL/TGs, which block leptin's ability to cross the blood-brain barrier. People are always talking about leptin resistance around here, but they're rarely mentioning fructose.
Hyperuricemia occurs as a result of the specific metabolic pathway of fructose. In short (sort of), fructose becomes phosphorylated to fructose-1-phosphate by fructokinase and fructose 1-p later becomes glyceraldehyde which is itself phosphorylated by triokinase to glyceraldehyde-3-phosphate. The reason why this minutiae matters is that these processes soak up so much phosphate that ATP is depleted since it can't be oxidatively phosphorylated from ADP and because it's utilized to make G3P. The enzymes that degrade AMP are no longer allosterically inhibited, so AMP breaks down to IMP which become inosine, which becomes hypoxanthine which becomes xanthine, which becomes uric acid. The precipitous decline in adenine nucleotides triggers a positive feedback mechanism that may fail at the IMP stage and cascade down again, creating more uric acid. The reason why any of this matters is that hyperuricemia leads to insulin resistance
If I were working for a pharmaceutical company and needed to create a pill that caused insulin resistance, leptin resistance (and thus, diabetes and obesity) I would just make it pure fructose and advise a high dose.
In spite of the information I came across, in digging deeper I have actually softened my position slightly on fructose. It would seem that the first problem (hyperleptinemia) can be prevented with exercise, and that the sedentary are the ones who would actually be affected by it.
I also found that the threshold for hyperuricemia appears to be at around .5g/kg of body weight. Staying below that point may be harmless, especially if sufficient ascorbate is consumed.
So to sum all of this up, exercise every day and take your vitamin C and you'll probably avoid most of the major effects of fructose. One thing to keep in mind however is that absorption by the liver isn't 100%, so some amount is making it into the bloodstream and potentially glycating proteins all throughout the body. The larger the dose, the more this would be a problem, so at the very least we may endeavor to stretch out the consumption of fructose-bearing foods over the course of the day.
You should be alarmed by the politics that Lustig is trying to utilize with fructose......but make no mistake about whether fructose in excess in our diet is very very dangerous. It is. And when you mix it with pufa intake.......it's the perfect storm.
Rats fed a diet of 45% sucrose, 30% casein, 20% lard, 4.5% salts, cod liver oil, dried yeast, and wheat germ, do not develop fatty liver or any other signs of disease http://jn.nutrition.org/content/3/1/61.full.pdf+html. Another nutritious diet (milk, yeast, coconut, etc) reported good general health of rats fed 67% sucrose http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1275514/pdf/biochemj00921-0130.pdf , but this amount of sucrose regularly causes problems in modern lab-chow fed rats. I think results contradictory to the above are due to rats being fed deficient diets.
Kitavans healthfully consume 11% of their diet as fruit (roughly 39 grams of sugar, depending on the fruit). 67% also comes from sweet potato, yam and taro. If 1/3 of their tuber intake consisted of sweet potato (this is speculation), then their total sugar intake would be roughly 61 grams sugar/day, or 12% of their total calories as sugar (~30.5 grams or ~6% total calories as fructose). For context, the mean American fructose intake is 55 grams or ~9% of total calories (although some segments of society consume more, reaching 15% to 20%).
But I wouldn't feel safe recommending a diet of 12% sugar unless the person was eating a nutritious diet (ex., choline aka beef liver/eggs/etc). In other words I believe the answer to 'how much fructose?' depends on how much nutrition you're consuming.
I do feel it's important not to wrongfully condem sugar because I feel there are some unique health benefits to sugar consumption.
People get caught up in Lustig's (misguided) policy recommendation...but you have to understand he's from San Francisco, the world capital in nanny state nonsense.
HOWEVER, if you watch his talks and understand the biochemistry, you can see why he's alarmed by fructose. I just watched his AHS talk this weekend and that's 100x more clear than his original you tube talk that everyone references.
There are two things that make me mad about the whole Lustig nonsense that always shows up:
1) his talks get the same "credibility" (or lack there of) rating as other non-scientists. He is actually more credible than most of the talks at AHS (see Lalonde's talk for why). He's right, and you can't just randomly dismiss him because he's actually done (or worked with colleges who have done) the biochemistry.
2) people dismiss his science because they don't like his policy. He can be right about the science and wrong about policy. He IS! (in my opinion). I totally respect his analysis of the biochemistry, and would point anyone to the work he's done. But at the same time, I'd go toe to toe with him getting the state involved in the control of fructose for anyone.
I guess there's a third thing too: I guess this goes with the Nikoley's "beware of your biases" comment. We're a select group of people who have bought into "grains are bad!" but if you talk to a "regular" person, they don't believe you because they "could never give up bread, it's healthy whole grains!". I see the same thing happening here. We have a guy (who's done the science) telling us maybe fruit isn't as good for us as we thought. But we're all "addicted" to fruit for our sweets and it feels good to us because it's "natural", and so we go all "I could never give up fruit" and then it's off to shoot the messenger.
Now, I don't know at what level fructose becomes toxic. There probably isn't enough research on that (or maybe I just haven't looked hard enough). But the biochemistry of the whole fructose-insulin-leptin interaction looks convincing to me to at least be wary of fructose and not call Lustig an alarmist.
I think fructose is ok in moderate amounts, on occasion and perhaps in large amount under some circumstances, in a metabolically healthy individual. The 'but' here is 'occasionally' not in the amounts the average person consumes in today's western society. We evolved to handle some fructose, that much is obvious, but not the toxic levels we find in the typical SAD. The whole obesity thing is not a one-trick-pony there are a myriad of factors at play and a toxic load on the body from any source will have a negative impact. The biochemistry speaks for itself, the conclusions we draw from that can vary due to interpretation bias.
I think there's a conflation of issues going on here. Lustig is talking about extremes (no obesity without sugar), while Aragorn is addressing the middle (normal people can handle some amount of fructose just fine). They're talking across each other to prove themselves right in their particular domain.
Yes, drinking a shitload of sugar is bad and probably plays a big role in obesity. Lustig is right about that. I think he's wrong to suggest that sugar in itself is the reason for all obesity. Aragorn is right that normal people can handle some amount of fructose, probably more than Lustig would say, but then he's wrong to basically dismiss it entirely and go back to energy balance. Zero-nutrient liquid energy deserves more attention when it comes to obesity than steak, but barebones calorie counting doesn't make a distinction.
I'm surprised nobody has brought this study up yet...
Shifting 25% of dietary calories from glucose to fructose caused a 4-fold increase in abdominal fat. Maybe not cause for alarmism but certainly it must be important?
Animals fed a low-fat, high-sucrose (LH) diet were actually leaner than animals fed a high—complex-carbohydrate diet. Fat was also found to be the critical stimulus for hyperglycemia and hyperinsulinemia in B/6J mice. In the absence of fat, sucrose had no effect on plasma glucose or insulin.
I know this is mice but it's still pretty interesting
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