Since I started grad school in physiology, I get a lot of questions from friends and family about the science that goes on in their daily lives. It's part of the reason why I decided to start blogging in the first place, to finally give people well-researched, thought-out, and long (yeah, they're usually very long) answers to their questions. I can't answer all questions, obviously, but when it comes to something I can research on Pubmed, the world is my oyster!
One of the questions I've gotten most often goes something like this: "What is high fructose corn syrup and why is it evil", or "I know high fructose corn syrup is evil, but why?" It's taken Sci a lot of time to think about answering these questions. It's not because I can't access the information, but rather because I know that, whatever I end up telling people, I'm going to get a response like "OMG! You are in the pocket of teh evil cornz industries!" or "You just hate corn! You are a horrible evil cornz haters!" The reality is that Sci is neither of these things.
But, despite possible repercussions on Sci's relationship with corn, I want to answer the question. Especially because the New York Times is bringing back the corn syrup debate. And so today, Sci will attempt to talk about High Fructose Corn Syrup (HFCS). In an effort to check this out I did a big literature search. I was careful to choose articles from researchers that didn't receive company money as well as those that did. Citation list will be at the end.
First of all, what IS HFCS?
Actually, HFCS is actually kind of a misnomer. But we'll start with the basics. As you might know, there are two main kinds of monosaccharide sugars that we utilize in our diets: glucose and fructose.
Glucose, via wikipedia.
Fructose, via wikipedia.
Combine glucose and fructose together, and you get the awesome, the dynamic: SUCROSE, otherwise known as common table sugar.
Sucrose, via wikipedia. See the pretty little linkage?
Since sucrose is a 50/50 joining of glucose and fructose, it's exactly 50% of both.
So what is HFCS, and how does it compare?
HFCS is basically a corn syrup which has been exposed to enzymes which increase its fructose content. It's then mixed with 100% glucose. The glucose and fructose bond. BUT, there's more fructose than there is glucose, and so there's some extra free fructose floating around. The final results is something pretty similar to sucrose. Only not. There are two kinds of HFCS in major dietary usage:
HFCS-42: 42% fructose and 53% glucose. With some extra stuff. This has some unbound glucose instread of fructose. Used mostly to sweeten baked goods and other sweets.
HFCS-55: 55% fructose and 42% glucose. With some extras. This has unbound fructose instead of glucose, and is the big sweetener in soft drinks.
The net result is not THAT different from sucrose. And you can see that "High Fructose corn syrup" is a bit of a misnomer. Sure, it's highER than sucrose, but it's not what I pictured. When I pictured HFCS, I was thinking of something that was 90% fructose or something. Instead, the fructose levels are just a little higher than table sugar. But does that higher dose of fructose make a huge difference?
How sweet is sweet?
Many people worry about HFCS because they worry that it is sweeter than sugar. This means that we like it more, and thus will drink more of it. Actually, though, we just like our world as sweet as we can get it. Sucrose and HFCS are pretty much the same by weight in terms of sweetness (HFCS may in fact be 1% less sweet). So the problem is not so much which one we're putting in, it's how much of it we're using. And how much ARE we using?
HFCS in your daily life
HFCS is everywhere. Since about the 1970's, it has had a drastic increase in popularity in the US. Right now, it's about even with sugar consumption, when we eat sweet stuff, about 50% of that is sugar and 50% is HFCS. It's grown in popularity because it's just so...cheap. As you may be able to imagine, the US is not the best place for growing sugar, and given the sweet tooth of America, we had to import a LOT. So sugar, we can't grow so well. But corn, corn we can GROW! HFCS making also takes a lot of technology, but technology we have in spades. Not only that, HFCS has the added advantage of being made entirely in syrup form. Sugar has to be dissolved into things before it can be used, while HFCS is already there and just has to be diluted. It's useful and it's cheap, of course companies jumped on it.
But is it good for you? Is it bad for you? How much of a difference does that extra shot of fructose make?
Most of the studies that I've found that focus on the effects of HFCS and sugar focus on the effects of fructose, as opposed to the combined effects of HFCS and sugar. This is actually kind of a problem. It means that people get all up in arms about fructose, and then they hear "high fructose corn syrup", put two and two together, and the next thing we know, we're hearing about how HFCS, and only HFCS, is going to destroy your children, steal your car, and have an affair with your wife. But it's not just HFCS. Remember that fructose is in regular sugar, too, and the amounts aren't so different.
But the fact is, fructose gets a bad rap. And it's not undeserved. To get really basic with it, your body knows very well how to absorb glucose. And it absorbs fructose in the same way. But there are fundamental differences between these two molecules, and so the results can be a bit different.
As you might know, glucose consumption (when you eat sugars or carbohydrates in any form, which basically means when you eat food) increases levels of insulin being produced in the pancreas. This is because glucose can't actually get into the cells of the body on its own. Instead, it stimulates production of insulin, which causes glucose transporters to head to cell membranes, so the cells can take into the glucose circulating in the bloodstream.
The production of insulin also has several actions elsewhere in the body. Higher levels of insulin circulating to fatty tissues will increase production of leptin, a hormone that in turn will decrease levels of ghrelin coming from the hypothalamus. Ghrelin is a hormone that helps to regulate appetite, and decreasing it will decrease feelings of hunger and increase feelings of satiety.
So that's how the body absorbs glucose. Fructose is very similar. But. In high levels fructose doesn't stimulate as much insulin or leptin. When leptin levels are low, ghrelin levels will stay HIGH, and you won't get the feelings of satiety that you usually get with consumption of glucose. This means that if you eat fructose, you'll be a bit more likely to keep eating.
People have taken this information about fructose and run with it. If you're likely to keep eating, you're more likely to maintain a positive energy balance. If you don't use that energy, it goes to fat, and then OMG fructose is entirely responsible for the obesity epidemic in America!!!!
This really isn't necessarily true. Fructose DOES produce these problems, but only when fructose is not tempered with something like, say, glucose. And fructose is ALWAYS served with glucose. This is partially because of metabolism, and partially because of sweetness. It's also because pure fructose alone causes "severe gastrointestinal distress". You don't WANT to be eating pure fructose, and you almost never do. So you have to keep in mind that when you're looking at sugar or at HFCS, you're looking at fructose, but you are also looking at glucose, in almost equal measure.
So is HFCS evil?
I would say that fructose alone isn't good for you. But I wouldn't say that HFCS is evil. Sucrose has almost as much fructose as HFCS. Not only that, I haven't found a single study comparing HFCS to sucrose that has found any difference in how much people consume or their health stats afterward. The increase in HFCS has correlated with an increase in obesity in the US, but correlation is not causation. We've also had an increase in the number of people leading sedentary lifestyles, the number of people who own cars and drive everywhere, and the number of McDonald's chain restaurants. Correlation is not causation, and though the jury is still out on high amounts of HFCS, it doesn't look like it's much worse than anything else we're doing.
The big problem, I would say, is that there's just so much out there that's just so sinfully sweet. Everything we eat is sweetened, whether it be with sugar or with HFCS, and we're eating and drinking far more sweetened stuff than any group of people has ever done before. Sugar and HFCS can account for up to 24% if your daily calories. That's a LOT of sugar. And sugar, or its HFCS equivalent, is almost all the processed foods you pick up at the store. It comes down to the same old story. It's not what you're eating. It's how much. It's not whether it's sugar or HFCS. If it's listed as one of the top three ingredients on the back of the package, and it's not sugar or candy, you may want to consider putting it down.
1) Melanson KJ et al. "High-fructose corn syrup, energy intake, and appetite regulation." Am J Clin Nutr. 2008 Dec;88(6):1738S-1744S. Review.
2) Vos MB et al. "Dietary fructose consumption among US children and adults: the Third National Health and Nutrition Examination Survey." Medscape J Med. 2008 Jul 9;10(7):160.
3) White, JS. "Straight talk about high-fructose corn syrup: what it is and what it ain't. Am J Clin Nutr. 2008 Dec;88(6):1716S-1721S. Review.
4) Stanhope KL, Havel PJ. "Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high-fructose corn syrup." Am J Clin Nutr. 2008 Dec;88(6):1733S-1737S.
5) Bray, GA. "Fructose: should we worry?" Int J Ob, 2008 32, S127-S131.