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.