On May 30, New York City’s mayor Michael Bloomberg shocked soda industry trade groups and soda-drinking citizens alike by announcing his proposal to ban sales of sweetened beverages exceeding 16 ounces in the city’s restaurants, delis, movie theaters and sports arenas. It’s a novel idea. So far the boldest restrictions attempted (without success) by other cities to curb soda consumption have come in the form of modest beverage taxes. But Bloomberg’s dose-makes-the-poison approach targets portion size rather than just product.
He unveiled his plan with spiffy visual aides depicting amounts of sweetener found in small to large sizes of soft drinks. Sugar cubes were stacked like Mayan temples in front of gargantuan fast food fountain soda cups, and appropriate units of individual sugar packets were piled before their correspondingly sized beverage cans and bottles. A few decades ago these visuals would have been literal representations of the drinks’ contents, but today, in the United States, they are mostly figurative. There’s little or no sugar in a big gulp. Our modern sodas are sweetened with a mysterious substance called high-fructose corn syrup.
High-fructose corn syrup (HFCS) is swimming in sticky controversy, with some claiming it to be a contributing or even driving factor in the country’s disastrous obesity rates (thus the Bloomberg administration’s crackdown on super-sizing). It’s rapidly becoming the most reviled food ingredient since MSG. What exactly is this stuff? How did it become the nation’s staple soda sweetener? And is it really more evil than sugar?
Chemistry before history
To properly discuss HFCS, we first need to do a brief review of sugars in general. I’ll keep it quick and painless, I promise.
Basically, you’ve got your monosaccharides (single sugars) from which longer chains (disaccharides and polysaccharides) are built. For our purposes today, glucose and fructose are the only monosaccharides that matter. Readers, meet glucose and fructose:
They’re structural isomers of one another, which means they contain the same atoms (chemical formula C6H12O6) but those atoms are arranged differently.* See how their double bonds occur at different spots along the chain? In chemistry, such small structural differences can result in big differences in function. Just as the words “cat” and “act” contain the same letters but have different meanings, glucose and fructose behave differently in the lab and in your body. The ordering of atoms affects what shape rings they form (they spend most of their time as rings) and even how they taste, but more on that in a bit.
When one glucose molecule bonds to one fructose, a disaccharide called sucrose is formed. This is what we refer to as “table sugar” and what Bloomberg used to showcase the egregious volume of sweeteners found in large drinks. Prior to the advent of HFCS, sucrose was the predominant sweetener in U.S. soda.
The rise of HFCS
High fructose corn syrup production begins with making syrup from cornstarch. This initial stage corn syrup† is mostly glucose, and you can find it in the supermarket (pro tip: mix with red food coloring to make cheap and very convincing fake blood). This syrup is then isomerized (i.e., atoms shuffled around) to convert some of the glucose into fructose.
The process was originally introduced in 1957, but it didn’t take off right away. There are actually three types of high fructose corn syrup out there, named for their fructose content: HFCS-42 (42% fructose), HFCS-55 (55% fructose) and HFCS-90 (you guessed it, 90% fructose). HFCS-42 was the first to be created and is still used today in processed foods and some beverages.
HFCS-90 is made by passing HFCS-42 through an ion exchange column designed to retain more of its fructose component. The primarily-fructose product that results isn’t used as a sweetener, but rather is mixed with HFCS-42 to generate HFCS-55. (Starting to get the impression that sodas are created in a mad scientist’s laboratory with lightning striking in the background?) The intermediately sugary HFCS-55, introduced in the late 1970s, is the most commonly used sweetener in U.S. soft drinks.
This fine tuning of HFCS manufacturing occurred during a period in U.S. history when sugar was becoming more expensive (in part due to trade restrictions) and corn cheaper. Farm subsidies encouraging farmers to produce as much corn as possible resulted in excess supply and thus falling prices. Manufacturers stood to save money by switching to corn-based ingredients. In 1980, Coca-Cola began using HFCS in its beverages, and by the mid 80s most other soft drink companies had followed suit.
As early as the mid-1990s, I recall friends insisting the Coca-Cola from Mexico (which allegedly was still sweetened with sugar) tasted better than the U.S. version, and going significantly out of their way to purchase the Mexicoke. Such preferences were not lost on soda makers. Pepsi now offers a product called “Pepsi Throwback” – a cola sweetened with good old-fashioned sucrose, just like mom used to make.
But taste isn’t the only issue. Concerns have been raised that HFCS might be worse for human health (and weight) than sucrose. High fructose corn syrup’s image problems have gotten sufficiently dire that the Corn Refiners Association recently petitioned to have the product re-christened as “corn sugar”. The FDA shot down the idea, to the delight of HFCS critics but also the sugar industry, citing that “sugar” is a dried, crystallized substance while HFCS only exists as a liquid. They also pointed out that the name “corn sugar” was already being used to describe an all-glucose corn sweetener. Oops.
Is HFCS sweeter than sucrose?
This question is harder to answer than you’d think. Some researchers state that HFCS is sweeter than sugar, and that this super-sweetness may entice consumers to drink even more HFCS-sweetened beverages. Others (some of them with HFCS industry affiliations) argue that this is a misconception and that there is no meaningful difference between the two products.
At least everyone does seem to agree that fructose tastes sweeter than glucose, so let’s start from there. In terms of sweetness, fructose > glucose.
Fine. And what about sucrose? Well, since it’s a disaccharide composed of one fructose and one glucose, dissolving it into water (i.e., soft drinks) will you give you a pretty even 50/50 mixture of glucose and fructose. So sucrose should be sweeter than humdrum glucose but not as cloying as mega-sweet fructose. Fair enough.
fructose > sucrose > glucose.
And now the hard part. Let’s stick to soda sweeteners since they’re the focal point of so much quarreling. You will recall that HFCS-55 is 55% fructose. So it should be a little sweeter than sucrose but not a ton. You probably won’t even notice. Here, we’ll employ some amplitude-denoting greater-than symbols:
fructose >>> HFCS > sucrose >>> glucose
Sure, that looks about right.
But wait, there’s a possible complication. HFCS isn’t simply a disaccharide dissolved into water like sucrose. It’s a crazy science experiment, remember? So how sure are we that a bottle labeled HFCS-55 actually contains 55% fructose? Well… a 2010 study in the journal Obesity attempted to measure fructose contents in a variety of soft drinks, and that is not what they found. Some drinks contained less than 55% fructose, but more exceeded that value. The highest recorded fructose amount was 65% and the mean was 59%. Experts have pointed out some flaws in this study (join the club, soda study, we’ll soon see that there is a lot of iffy research in this field), but much of these had to do with just how hard it is to accurately do this type of measurement, which brings us back to questioning our certainty about that 55% claim. So is HFCS sweeter than sucrose? Maybe?
Is HFCS making people fat?
The United States leads the developed world in both HFCS consumption and obesity, and both have climbed precipitously since the 1970s . But we can’t assume a causal relationship just from the correlation. After all, a lot of other things happened over the past few decades: increased portion sizes, more dining out, better video games, ketchup as a vegetable, pizza as vegetable, sandwiches with fried chicken instead of bread.
So is there any experimental evidence of HFCS’s fat-fueling edge? Yes, and no, and yes again, and so forth. It’s a hotly debated topic and so far the science doesn’t seem to be reaching a clear consensus. For every one study finding a connection between HFCS and obesity, there are a dozen retorts picking apart the methodology used by the researchers. For instance, a 2010 Princeton study reporting that rats given HFCS gained more weight than those with access to sucrose was met with a flurry of criticism, and not all of it from HFCS industry supporters.
Since the primary chemical difference between sucrose and HFCS is the percent of fructose, some researchers are focusing on studying the effects of fructose, as opposed to just HFCS. Glucose and fructose are metabolized differently by the body (e.g., fructose metabolism is not insulin dependent), so it seems reasonable to suspect they might have different effects on fat production. But here too the data are not exactly convincing. A 2012 meta-analysis‡ of fructose studies published in Annals of Internal Medicine found that fructose consistently led to weight gain in hypercaloric experiments (those in which fructose was given in addition to existing daily calorie intake) but not in isocaloric experiments (those swapping fructose for other sugar sources). This suggests that sugar calories in general, rather than specific sweeteners, were responsible for weight gain.
But there is a psychological component that such analyses might be missing. Humans consuming sugary beverages don’t methodically log those calories and then subtract accordingly from subsequent snacks encountered during the day. Typically a soda is just added to the heap of caloric intake as though it were water or unsweetened tea. And as more of such drinks are consumed, more uncompensated empty calories sneak into the average diet. Given this, we might consider if mayor Bloomberg – currently the butt of many media jokes, including advertisements with his frowning face Photoshopped onto the body of a prim middle-aged nanny – may actually have the right idea. His administration is focusing on a commodity that has become so cheap to produce that soda manufacturers can offer it in buckets almost as easily as in cups, and attempting to reduce the ease of passive calorie acquisition.
Of course, HFCS isn’t the only product made from cheap corn. Corn isn’t even the only crop whose prices have been driven down by U.S. farm subsidies (soy and wheat, among others, are also producing heavy yields). These plentiful goods make their way into processed snacks and cheap feed for livestock – two more potential contributors to America’s expanding girth. Singling out one dietary hazard to the exclusion of others has the potential to create a lot of confusion and polarized opinions. I’m not a huge fan of HFCS myself, but one of the downsides of its lousy public image is that it has opened the door for sugar manufacturers to market their product like it’s some kind of health food. “Made with real sugar.” Great.
* There are also enantiomers of these molecules, but seriously, how much chemistry do you want in one article?
† Be careful not to confuse corn syrup with HFCS. It may be quicker to say “corn syrup” when you actually mean “high-fructose corn syrup”, but they’re very different products.
‡ Meta-analyses are like greatest hits compilations of previous scientific studies. The authors review a bunch of papers on a given subject, rate their quality and discuss any overall trends found by comparing the studies.
As a child, Alex Reshanov was told by grown-ups that she should consider becoming a lawyer (tendency to argue) or a comedian (frequent joking), so naturally she opted for science writing. In 2010, she started a personal blog, Blogus scientificus, as an outlet for her diverse scientific interests, random pop culture trivia and various phobias. Many of her posts have been published at EarthSky.