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Author Topic:   High-Fructose Corn Syrup - the Controversy
crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 1 of 47 (581206)
09-14-2010 1:32 PM


One of my goals as I study biochemistry is to be able to apply it to my life, and I've been left utterly mystified by the controversy about high-fructose corn syrup.
On the one hand, I've seen a number of scientific studies indicating that rats fed water sweetened with HFCS consumed more diet and apparently absorbed more calories from the same amount of diet than rats on water sweetened with sucrose. That would seem to implicate HFCS as not being "the same as sugar."
But I've also studied glycolysis in my classes, and I've been looking up human sugar digestion, and I just can't see any way that the extra 5% of fructose in HFCS could possibly make a difference. There's no mechanism to explain things like the rats study I linked to, above. HFCS enters the bloodstream as free fructose and glucose, but so does sucrose; the glycosidic linkage is broken by stomach acid and sucrase long before it enters the intestine. If the 5% difference means so much why don't we see the same suggested effects when people consume honey, which has roughly the same fructose/glucose ratio? Why don't we see the same suggested effects in the consumption of fruit, which are sweet primarily as a result of fructose - the "fruit sugar"?
Obviously the question isn't "is HFCS bad for you", the question is "is HFCS worse than sucrose"? That's the notion driving the anti-HFCS crusade and the popularity of things like "Pepsi Throwback", the sweetened-with-sucrose version of Pepsi. (I'm sure Buz will jump in to remind us how much his health improved ever since he stopped consuming refined sugars at all, and he's probably absolutely right about that.)
Personally, I can't taste the difference (though I started out thinking that for sure I could) and a summer of complete abstention from the stuff had no discernible effect on my weight, my health, my "wellness"/energy level, or anything. Without an actual mechanism I don't understand how these results can really be real.
I'm hoping the more experienced chemists can weigh in with their thoughts and a clearer notion of the metabolic effects at play, here. All I can conclude right now is that I should switch to a different soda to feed my rats.*
*I don't have any rats.

Replies to this message:
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 Message 3 by DBlevins, posted 09-14-2010 3:08 PM crashfrog has not replied
 Message 4 by purpledawn, posted 09-14-2010 4:27 PM crashfrog has replied
 Message 7 by Buzsaw, posted 09-14-2010 5:29 PM crashfrog has not replied
 Message 15 by onifre, posted 09-21-2010 1:22 PM crashfrog has replied
 Message 23 by Hangdawg13, posted 10-17-2010 10:27 PM crashfrog has not replied

  
crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 5 of 47 (581225)
09-14-2010 4:46 PM
Reply to: Message 4 by purpledawn
09-14-2010 4:27 PM


Re: Too Much Sugar is Too Much Sugar
Agreed that too much sugar is bad.
But these links seem completely bogus:
quote:
High sucrose diets cause diabetes because of the bodys inability to metabolize large quantities of sugar. Insulin is generated in the body for sucrose metabolism, breaking the sugar down in to small parts useful for producing energy. When large quantities of sugar are consumed, the body loses the ability to pump in enough insulin to handle or manage it over a long period.
I don't think even a single part of this has sound biochemistry behind it. They make insulin sound like a catalytic enzyme, but it's actually just a hormone that signals glucose uptake by your cells. Diabetes is caused when either an autoimmune attack against your islet cells destroys their function, or your cells become so accustomed to high levels of insulin (due to sugar and starch in your diet) that they begin to become "resistant" to it, and require more insulin to trigger the same level of glucose uptake.

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 8 of 47 (581231)
09-14-2010 5:32 PM


I'd like to just go ahead and reiterate that I'd like this to be a topic about biochemistry, human metabolic pathways, and scientific evidence for the potential harmful effects of HFCS (whatever they're supposed to be), not people's homespun dietary advice or their political notions about American agriculture.
Thanks guys, really, but I'm looking for science here, not recipes.

Replies to this message:
 Message 9 by Buzsaw, posted 09-14-2010 9:00 PM crashfrog has replied

  
crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 10 of 47 (581280)
09-14-2010 9:39 PM
Reply to: Message 9 by Buzsaw
09-14-2010 9:00 PM


I took that to mean you wanted information as to what would make your life more healthy and disease free.
My apologies for being unclear, I guess, but my intention was to have a thread about human metabolic pathways for sugars. I'm not looking for advice; that was just the context that prompted me to open the thread.

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 16 of 47 (582691)
09-22-2010 9:02 PM
Reply to: Message 15 by onifre
09-21-2010 1:22 PM


Well, that's fructose, though, not HFCS which is only 55% fructose.
Recall that fructose, or "fruit sugar", is the primary sugar in fruits so shouldn't fruits make you fat?
Have you ever heard of someone getting fat from fruit? Getting diabetic from fruit? Me neither.
That's the mystery, I guess; according to the food scare crowd, fructose (fruit) is ok, and fructose+glucose (sucrose) is ok, and glucose is ok, but 55% fructose/43% glucose gives you instant diabetes.

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 19 of 47 (582820)
09-23-2010 4:03 PM
Reply to: Message 17 by purpledawn
09-22-2010 9:39 PM


Re: Fructose Metabolism
But not worse than sucrose.
Right?

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 Message 21 by jamesio, posted 10-16-2010 4:16 PM crashfrog has replied

  
crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 22 of 47 (587228)
10-17-2010 8:00 PM
Reply to: Message 21 by jamesio
10-16-2010 4:16 PM


Re: Fructose Metabolism
As you can see fructose and glucose share the majority of the Embden-Meyerhoff-Parnas pathway.
Fructose breakdown does not have this feedback mechanism, so energy and fat production depends solely on the presence of fructose.
Doesn't that strike you as evolutionarily untenable, that human beings would completely lack any kind of regulation of our fructose intake given the near-universality of fructose as a natural sugar in fruits? I mean, we're apes. The ape diet contains a ton of fruit.
And it's all very well and good to say that fructose isn't subject to feedback satiety, but fructose is almost never eaten in isolation - in sugar, in corn-based sweeteners, and in honey, fructose comes with a nearly-equal amount of glucose.
And it seems highly contradictory to posit that "fructose doesn't elicit an insulin response, hence you keep eating it" (even though you're not just eating fructose ever; you're consuming it either with equal parts glucose, or with starches, fibers, protein, and fats, which do elicit satiety) on one hand, and then posit "fructose causes Type 2 diabetes by creating the persistent high insulin levels that lead to T2 insulin insensitivity."
I mean, which is it? I'm not accusing you of making both, or either, arguments, but both of those arguments are made by fructose's opponents, frequently simultaneously. I don't see how it can be both.
And, look, fructose is regulated by fructose-6-phosphate inhibition, just like glucose.

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 24 of 47 (587246)
10-17-2010 11:40 PM


Guys, look - if the only thing you know about human metabolism of HFCS is that "the liver processes fructose differently", thanks for contributing, honestly, but you're not exactly who I want to talk to on this subject. And we covered the liver's metabolism of fructose already. We know that the liver "processes fructose differently." But HFCS and sucrose have almost the same amount of fructose and glucose.
I'd like to try to square what I've studied as an undergraduate biochemistry major with a semester of metabolism with the claims of the anti-HFCS crowd, if possible. But if you don't know what "Embden-Meyerhof-Parnas pathway" means, for instance, then again - thank you very much for your interest but I'm looking for contributions from a greater level of expertise. No offense.

Replies to this message:
 Message 28 by Taq, posted 10-18-2010 4:41 PM crashfrog has replied

  
crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 27 of 47 (587349)
10-18-2010 1:47 PM
Reply to: Message 26 by DBlevins
10-18-2010 1:30 PM


The issue for me at least is the fact that the BT toxin has been found in streams some distance from the GM crops.
The Bt "toxin" is just a protein, and it's harmful only to lepidopterans and beetle larva, and only in the basic pH of their foregut.
Iirc they are lookiong into doing some research into what effects the BT toxin has on insect populations in these streams and other riparian ecosystems.
Cry1Bb isn't a bioaccumulating compound, it's just a protein. Proteins out in the natural world hydrolyze rapidly, or are scavenged by microflora. The safety and low ecological impact of Bt toxin is why it's one of the pesticides that organic farmers can spray.
That's right - organic farmers spray Bt "toxin" all over their crops. But you think the major source of Bt in runoff and streams is GMO corn. Once again, the conventional farmer is slammed for consequences that organic farming exacerbates. Hoocoodanode indeed?
Because sucrose is made up of both glucose and fructose less overall must be processed by the liver.
But HFCS is also made up of both glucose and fructose, at almost the exact same proportion as in sucrose. So why would there be a difference?
that the liver starts storing fats that accumulate in the liver and inhibit proper insulin production and increase LDL in the blood.
Did you see what I said before? One of you is telling me that high fructose in the diet causes insulin upregulation and therefore diabetes, due to acquired insulin sensitivity. (So-called "metabolic syndrome" or sometimes "pre-diabetes.") Now you're telling me that high fructose in the diet suppresses insulin, causing... something. Fats, I guess.
I continue to believe that the food-scare hysteria surrounding fructose and HFCS is founded on no sound science, and it's for this reason - if there were some sound science counterindicating HFCS, food-scare proponents would be able to agree on what was bad about it.

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 29 of 47 (587392)
10-18-2010 5:16 PM
Reply to: Message 28 by Taq
10-18-2010 4:41 PM


It is the fact that fructose is ONLY processed in the liver.
I don't think that's true. Fructose in muscle and kidney tissues can enter glycolysis by phosphorylation by hexokinase. It has a slightly different pathway in the liver (utilizing fructokinase instead) but Lehninger's Principles of Biochemistry is pretty clear that fructose metabolism occurs in muscles. It's a fact that the glycolytic pathway has a lot of feed-ins, because the critical intermediate - phosphorylated fructose - can be formed from a wide variety of hexoses by easily-reversible isomerizing reactions.
Is it as prominent as traditional glycolysis? No idea.
However, excess triglycerides are take up by adipocytes and stored as fat, hence fructose caused obesity.
But, again, we're not talking about pure fructose - we're talking about blends of nearly equal glucose and fructose. (I'm wondering why I have to constantly push back the efforts to conflate HFCS and pure fructose.) For the seventh time, or so: I grant the connection between sugar and obesity. Any hexose digestible by the body is going to wind up as pyruvate and acetyl-CoA, once glycogen is "full." What's the connection between HFCS-55 specifically (55% fructose, 43% glucose) and obesity that isn't present for sucrose (50% fructose, 50% glucose)?
I didn't think that I was unclear on the OP, or that I phrased the question in an unclear way. Taq, can you help me understand the difficulty you're having with the parameters of the topic?

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 Message 28 by Taq, posted 10-18-2010 4:41 PM Taq has replied

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 31 of 47 (587582)
10-19-2010 3:43 PM
Reply to: Message 30 by Taq
10-19-2010 2:16 PM


The question is whether this increase in fructose over an even balance like that with pure sucrose is enough to increase TG levels and subsequent obesity.
And the answer is "no, it isn't." In about half a dozen reviews of the evidence researchers have never been able to find evidence of increased TG levels, or a connection between consumption and obesity, at fructose consumption levels that represent actual human use:
quote:
The purpose of this review was to critically evaluate the existing database for a causal relationship between the ingestion of fructose in a normal, dietary manner and the development of hyperlipidemia or increased body weight in healthy, normal weight humans, using an evidence-based approach. The results of the analysis indicate that fructose does not cause biologically relevant changes in TG or body weight when consumed at levels approaching 95th percentile estimates of intake.
Evidence-based review on the effect of normal dietary consumption of fructose on development of hyperlipidemia and obesity in healthy, normal weight individuals - PubMed
quote:
Epidemiological studies show growing evidence that consumption of sweetened beverages (containing either sucrose or a mixture of glucose and fructose) is associated with a high energy intake, increased body weight, and the occurrence of metabolic and cardiovascular disorders. There is, however, no unequivocal evidence that fructose intake at moderate doses is directly related with adverse metabolic effects. There has also been much concern that consumption of free fructose, as provided in high fructose corn syrup, may cause more adverse effects than consumption of fructose consumed with sucrose. There is, however, no direct evidence for more serious metabolic consequences of high fructose corn syrup versus sucrose consumption.
Metabolic effects of fructose and the worldwide increase in obesity - PubMed
The question is how an increase in overall fructose consumption can lead to higher rates of obesity and other health problems.
But that's not the question I've been asking at all. (Hence my concern that you've misunderstood the topic.) What I'm asking is, is there evidence that replacing sucrose with HFCS in your diet is harmful? Or that replacing HFCS with sucrose in your diet is helpful? Conflating HFCS with pure fructose simply confounds the issue. I mean, it's right there in the thread title - we're talking about HFCS 55, the most common sweetener in (among other things) sodas.
In the OP you linked to a mouse or rat study where they found higher weight gain in the HCFS group compared to the non-HCFS group.
One of the things I'm learning as I do more research on the subject is that the human applicability of rat dietary studies is fairly limited.

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 Message 30 by Taq, posted 10-19-2010 2:16 PM Taq has replied

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 34 of 47 (587589)
10-19-2010 4:43 PM
Reply to: Message 33 by Taq
10-19-2010 4:32 PM


Wouldn't an increased risk of obesity related illnesses qualify as "harmful"?
I guess it would be, if replacing sucrose with HFCS would cause that. Does it?
I am clearly talking about an increase in fructose concentrations as compared to pure sucrose.
What increase? Sucrose isn't being replaced pound for pound by HFCS; HFCS is naturally sweeter than sucrose so it takes less HFCS to replace the sucrose in a food.

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 35 of 47 (587592)
10-19-2010 5:01 PM
Reply to: Message 32 by DBlevins
10-19-2010 4:16 PM


Should we worry about the possible unintended poisoning of targetted species outside of the farm?
Yes, but toxicity exposure is going to be limited to species that eat Bt crops or live in water where the toxin is present, right? We're not talking about something like a PCB that accumulates its way up the food chain.
Would you consider 6 months as low persistance?
Yes, I would.
While I applaud the attempt at creating pesticides that are low impact, with low-toxicity to non-targetted species and have a small to negligable impact beyond their application, I champion the continued oversight of any product or design which has the potential for negative consequences.
I'm down with oversight, just not with overreaction. Any kind of pest control measure is going to have to be monitored for emergence of resistance.
I'm not out to demonize the use of Bt in pesticides or our crops, but I definitely care about the possible negative consequences of their use. I think a high priority item for study should be the impact of the Bt protein in streams and the possiblility of the introduction of GM genes into native species.
Bt is a soil-dwelling organism. It's not like it's something we invented. Bacillus thuringiensis is all over the damn place; is this really the first time it's ever been in a stream? If we find it in a stream do we know for sure it's from Bt crops? I find all of that very hard to believe.
The increase in the percentage of foods that have sugar in their ingredients should be the focus of poeples ire and not the little difference between sucrose and HFCS.
While it's abundantly clear that the past several decades of public health intervention into the diet of Americans has resulted in an increase in calories consumed, it's not clear that the increase is due only to an increase in carb consumption (starches and sugars.) In fact it appears that consumption is up across the board - protein is up, fats are up, carbs are up, everything is up (but fruits and vegetables, natch.)

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crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 38 of 47 (587612)
10-19-2010 6:44 PM
Reply to: Message 36 by DBlevins
10-19-2010 6:12 PM


Just because it only effects a limited set of species doesn't mean we should not be concerned, right?
I'd turn it around and ask - if it only affects a limited number of species, how concerned should we be?
If the effect of Bt is creating an imbalance in off-the-farm ecosystems by killing a significant number of the targetted species I have to be concerned.
Why do you think it's creating an "imbalance"?

This message is a reply to:
 Message 36 by DBlevins, posted 10-19-2010 6:12 PM DBlevins has replied

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 Message 40 by DBlevins, posted 10-19-2010 7:04 PM crashfrog has replied

  
crashfrog
Member (Idle past 1466 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 39 of 47 (587613)
10-19-2010 6:45 PM
Reply to: Message 37 by Taq
10-19-2010 6:21 PM


No matter the overall intake the fructose fraction of the carbohydrate balance is still going to be higher in HFCS compared to pure sucrose.
Why? I don't follow.

This message is a reply to:
 Message 37 by Taq, posted 10-19-2010 6:21 PM Taq has replied

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 Message 42 by Taq, posted 10-20-2010 12:39 PM crashfrog has replied

  
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