Monday, February 02, 2009

Some Research on High Fructose Corn Syrup

I've been hearing a lot lately about high fructose corn syrup. A lot of the comments on various blogs that reported on the mercury contamination issue (including my own post on the subject) said something to the effect of "mercury or no, there are lot of good reasons to avoid HFCS".

As I said in my comment on my original post, I have never bothered to do the research to have a firm opinion on the subject of HFCS. Today, I decided to start to change that. Afterall, while I don't consume much HFCS, it is in my favorite brand of yogurt (which Pumpkin also eats) and in the Nutrigrain bars that Pumpkin loves and expects at day care pick up time. Should that bother me?

I have heard two main charges leveled at HFCS:
1. It is making us fat, and doing so more than other, more "natural" sugars would.
2. It is contributing to the corn monoculture on American farms, and this monoculture is bad for the environment and/or our food security.

I decided to start with the first charge, because I know a heck of a lot more about biochemistry than I do about farm policy (this is not really saying much- I don't know much about farm policy, and what I do know comes primarily from having read The Omnivore's Dilemma, by Michael Pollan. I never really think I "know" anything that comes from only one source, even one as well-written as Pollan's book.)

So, is HFCS making us fat? I did a PubMed search to see what the latest literature says. I found several reviews and study reports indicating that fructose (clearly a component of high fructose corn syrup) might in fact lead to greater weight gain than equivalent calories consumed as glucose. This perspective article from a former editor of a nutrition journal summarizes some of this evidence. In addition to the evidence summarized in that perspective, I found some studies indicating that levels of the hormones that control our appetite are different after fructose consumption than after glucose consumption ( this abstract summarizes some of these studies).

Sounds pretty damning, doesn't it? However, HFCS' "competition" isn't glucose, it is sucrose, which is a complex sugar composed of one fructose and one glucose. The fructose to glucose ratio in HFCS is 55% fructose to 45% sucrose, and as this abstract states, "The fructose:glucose (F:G) ratio in the U.S. food supply has not appreciably changed since the introduction of HFCS in the 1960s."

I also found several abstracts for studies that showed no change in metabolic parameters when HFCS consumption was compared with equivalent sucrose consumption. This study looked at metabolic parameters in subjects on different days, depending on whether they were fed fructose, glucose, HFCS, or sucrose. This study compared the effect of HFCS, sucrose, and milk (in which the main sugar is lactose, which is galactose + glucose). This study worked directly with sodas sweetened with either HFCS or sugar, and looked at "perceived sweetness, hunger and satiety profiles, or energy intakes at lunch".

I did a lot of this reading during my lunch break, and I felt a lot better about my HFCS sweetened yogurt as my research progressed. I don't think we can completely rule out differences between the metabolic treatment of HFCS and sucrose, but the preponderance of the studies I found indicates that HFCS is no more likely than sucrose to make you fat.

However, I also found a lot of studies that indicated both sucrose and HFCS are bad and that the increase in fructose in our diets (caused by an increased consumption of refined sugar, be that sucrose or HFCS) may indeed be contributing more to our growing waistlines and diabetes rates than you would predict purely from the calories consumed. So I should really switch to unsweetened yogurt. Too bad I don't like that! At least I don't drink a lot of soda. I prefer unsweetened seltzer water.

I also have heard that the argument Michael Pollan makes in his book In Defense of Food is that since we need an enzyme (sucrase) to break apart the fructose and glucose in sucrose but the sugars in HFCS are already broken apart for us, our digestion of sucrose is slower (or perhaps less complete?) than our digestion of HFCS. This is biochemically plausible, but I didn't find any studies about this. I also haven't read this book, so I am only working from second-hand accounts of the argument. I wold like to read the book, but am unlikely to have the time to do so anytime soon. Has anyone read it? Would you care to fill me in on his argument about the health impacts of HFCS? As I said above, I think I'll consider the environmental and food impacts separately. I'd also be interested to hear of any other arguments about the health impacts of HFCS. As of right now, I consider it much like I consider regular sugar- fine in moderation, but a source of empty calories.

Updated to add: I promised to tell you if I found any studies showing a difference between HFCS and sucrose. Well, one just came out. Here is my post about it.

11 comments:

  1. Dear Wandering Scientist,

    You may want to download the free journal article at Environmental Health so that you will have all of the information related to the topic of mercury in high fructose corn syrup. The Environmental Health journal is a peer reviewed journal. Nothing gets published without intensive peer review http://www.ehjournal.net/content/8/1/2 And while you're at it, you could do a little research on the role of Metallothionein-3 and look up Rao Ivaturi's paper on what happens to humans when they eat high fructose corn syrup. This should keep you busy for a while. :-) Enjoy.

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  2. @metallothionein- if you'd read the earlier post I linked to in this one, you'd know that I have read the Environmental Health article and was not particularly concerned by their findings, and didn't think the unreviewed study that piggybacked on this one in the press release had data to support its conclusions.

    Who is Rao Ivaturi? Was his study published in a peer-reviewed journal? If so, why don't you give me a link? My google search turned up this link to a dissertation: http://digitalcommons.unl.edu/dissertations/AAI8629533/, which actually says this: "...high fructose corn syrup feeding (HFCS) did not affect the mineral balances when compared to sucrose feeding." Are you perhaps confused about the difference between pure fructose and HFCS (which is part glucose, part fructose)?

    The papers I see in a quick search on metallothionein-3 are investigating a decrease in its expression in Alzheimer's disease. I didn't see anything linking this protein to HFCS, and I would need a fair amount of evidence to think that the absence of a bond between the fructose and glucose a person consumed has any impact on the expression levels of this protein.

    I'll listen to anyone's arguments on HFCS- but you've got to bring me evidence, not innuendo.

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  3. I read In Defense of Food, but I don't remember the details of what he had to say about high-fructose corn syrup. What I recall of his arguments were more global, and more pointing out the pitfalls of nutritional science and the faultiness of equating foods with the nutrients to contain. I'd say his number one take away was that a food is more than the sum of its parts, and we're safer sticking to actual foods rather than highly processed, food-like substances.

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  4. I just finished reading in Defense of Food, and I found it vaguely unsatisfying for a scientist. The book was more a non-technical proscription for how to choose what to eat.

    I read about a study ~ a year ago that debunked the HFCS and obesity link. The calories in HFCS are no more or less likely to make you fat as any other sugar. The problem is that you can ingest a whole bunch of calories without noticing it. You just don't get those saiety cues when you are sucking all those calories through a straw.

    I am worried about planting oceans of monocultures and our inability to contain the genes of star corn. Pollen drifts. Some people are deathly allergic to star corn, and we have no way to protect other corn fields.

    Let's bring back amaranth!

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  5. @badmomgoodmom- one of the studies I ready yesterday actually found that people drinking regular soda with their lunches decreased the rest of their calorie intake, but people drinking diet soda did not. I thought that was interesting. But I do think it is easy to drink a lot of calories quickly without realizing it.

    I find the ecological argument against HFCS the most compelling, but I wonder if that is just because I don't know enough to see any flaws. Any ecologists out there want to tell me why I should or shouldn't be worried about the corn monoculture?

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  6. Offhand I don't have the reference, but when I was doing a bit of research into fructose malabsorption several of the papers mentioned that there are 3 different preparations of HFCS. The one used in soda is the 55% fructose, but the one used in baked goods (which allows the dough to be frozen) has 95% fructose. They also mentioned that the fructose absorption pathways can be overwhelmed even in people who aren't technically fructose malabsorbers. Also, the GI specialist I was seeing mentioned that about 1/3 of people suffering from IBS respond to a low fructose diet.

    All that said, honey & agave syrup are both almost 100% fructose, and people have been eating honey around here for a lot longer than HFCS. On the other hand, like Michael Pollan points out, there's a ton of stuff that we don't know about food, that reductionist science isn't necessarily telling us. I think his main argument in "In Defense of Food" (which is a really short book) was that there are probably other things in food that we aren't aware of, beyond the calories, protein, fat, carbs, vitamins & minerals. And if we want to understand them we need to look at whole diets rather than just focusing on particular bits. Just think how hard that study would be to set up and control!

    Anyway, the end result of all my reading, for me, was that the only type of "food" I'm unwilling to let my daughter eat, is trans fat. Everything else, in moderation, doesn't look like it will cause long term problems.

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  7. On a slightly different topic, I've also heard what you mention about diet vs regular soda. The explanation that I'm remembering was that if you're drinking diet soda, your brain starts to associate the sweetness with "no calories". Apparently your brain is primarily responsible for telling you when you've had enough to eat, since it takes your stomach about 20 minutes to let you know it is full. So if you're consistently teaching your brain that sweet=not food...then sweet things stop making you feel full. I wish I had actual references for all this stuff, but I don't, and I don't have time right now to go track them down.

    Thanks for posting this, it is really cool to see what you found out.

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  8. Hi,
    My google alert for HFCS picked up your post. I like your multi-faceted approach. I strongly disagree that HFCS,specifically HFCS-55 is metabolically the same as sucrose, table sugar. Although the CRA claims that the ratio
    55%fructose:45%glucose is "similar"
    to sugar, the math proves that it isn't. 55/45=1.22 That means that everytime a teen chugs a Coke or Pepsi (bottled in the US) his liver is receiving the health "benefits" of 22% extra fructose, compared to glucose. Excess fructose over time leads to long term health hazards. Ditch HFCS, especially HFCS-55 which is used to sweeten all national brands of soda, flavored teas, lemonades (even Newman's Own),and ironically, many sports quenchers. Take care. btw: Honey is only about 58% fructose.

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  9. @Cynthia1770- the studies I've found so far don't show any evidence that our bodies "see" a metabolic difference between sucrose and HFCS. I'm still poking around the literature, and if I find anything that changes my mind, I'll definitely post about it. So far, though, I just don't think HFCS is the health worry it is being made out to be.

    I think the health worry is the large amounts of refined sugar- be it sucrose or HFCS- that we're consuming. There are plenty of studies that imply neither sucrose nor HFCS is good for us, metabolically speaking. If you want to blame HFCS for the increase in consumption of refined sugar (by making it cheaper), you may have an argument. I haven't done the research to have an informed opinion.

    The thing that is bothering me most about this current furor over HFCS is the fact that I now see people trading tips on how to get soda sweetened with sucrose. I don't think that is going to be a healthy thing, either. It bothers me to see people cloaking questionable health advice (replace HFCS with sucrose) in science, when the science doesn't really support that advice. The science- at least the science that I've read about so far- supports advice to limit the consumption of both HFCS and sucrose. But that is not what people are hearing.

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  10. Cloud, I echo your point regarding substitution of sucrose for HFCS - neither one is "healthier" than the other.

    I'm still really curious about the biochemistry of both sweeteners though, so I look forward to reading more! In the meantime, I'm going to stick with seltzer myself and keep cutting back on the sweeteners in general.

    Thanks again for your thoughtful comments over at my place.

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  11. I came over from the Mom-101 post and this is fascinating! Reading your post I feel like there is no underlying bias so thanks for that!

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