Corn is everywhere in American fast food

Blogging on Peer-Reviewed ResearchFast-food restaurants like to bedazzle consumers with choice, offering a smorgasbord of different foods and drinks with varying flavours and  sizes. And yet, these options have more in common than you might think. According to a new study, this multiplicity of choice hides the fact that the overwhelming majority of American takeaway food is actually based on a single source - corn. It provides food for the animals whose meat makes up the burgers, the oil for frying chips and the syrup that bulks out fizzy drinks.

Hope Jahren and Rebecca Kraft from the University of Hawaii discovered the omnipresence of corn by chemically analysing a variety of foods from America's top chains - McDonald's, Burger King and Wendy's. At six cities across the country, the pair bought hamburgers, chicken sandwiches and orders of fries. Returning to their lab, they analysed the levels of different carbon isotopes in each.

Analyses like these have proven to be a surprisingly good way of tracing the origins of foods. Like all plants, corn gets its energy through photosynthesis, but it uses a slightly different method to other important crop plants like rice, wheat or potatoes. This difference is reflected in a plant's ratio of two carbon isotopes - the common carbon-12 and rarer carbon-13. Corn has a signature ratio that sets it apart from other crops and by association, the meat of animals that consume it also stand out in the same telltale way.

Their results revealed that most of the cows and chickens that ended up in the burgers were fed almost exclusively on corn. Out of the 162 samples of beef they collected, only 12 came from animals that were potentially fed on other sources like grass or grains (and interestingly enough, all of these samples came from West Coast branches of Burger King). For chicken, there were no exceptions - they had corn for breakfast, lunch and dinner.

Jahren and Kraft also measured the levels of nitrogen isotopes in both the chicken and beef burgers. The high levels they found indicated that the animals were fed with corn that had been grown using nitrogen-based fertilisers, and that they had been reared in very confined spaces.

i-58fa3a3e8dffbda14f4f8138c7248706-Corn.jpgThe predominance of corn wasn't just restricted to meat. By subjecting fries to the same isotope analysis, the duo found that Wendy's cooks its fries almost exclusively in corn oil (contrary to the chain's claims), while Burger King and McDonald's use a mix of different oils. And we know that drinks (which weren't included in this study) are sweetened using high-fructose corn syrup. So ubiquitous is corn that out of the 160 items of food bought in Wendy's outlets throughout the country, not a single one could be traced back to a different food source.

The results are interesting in themselves, but why do they matter? You could argue that consumers have a right to know where their food comes from. Fast-food corporations are typically opposed to regulations that require them to report the ingredients in their food, even though they account for over half of American restaurants and despite the immensely calorific nature of their products.

And the fact that so much of said food can be traced back to corn has environmental implications. Corn feed is relatively cheap and provides farmers with a way of maximising the calories that their animals are eating for minimum cost. But corn agriculture in the US is encouraged by heavy government subsidies, but has been criticised for being environmentally unsustainable. It encourages heavy use of both fertiliser (as revealed by the nitrogen isotope analysis) and pesticides.

References: A. H. Jahren, R. A. Kraft (2008). Carbon and nitrogen stable isotopes in fast food: Signatures of corn and confinement Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0809870105


More like this

The results are utterly unsuprising to me, but the method is totally cool. I didn't know corn actually had a different isotope ratio than other plants.

Also, how do we know from this analysis that the fries were cooked in corn oil? Couldn't they just as easily have been cooked in beef fat from cows that had been fed corn?
Mind you, I'd much rather eat corn-oil fries than beef-fat fries.

Has anyone actually proposed a regulation requiring fast food resturants to not list just the ingredients of their foods, but the 'ingredients of the ingredients' (what the animals are fed), so to speak? That could be awfully difficult to pin down, but information consumers might be interested in.

Chips !!? The barely edible things that once contained potato and are served at US fast food establishments should never be referred to as 'chips'. That would imply that they are food.

By NoAstronomer (not verified) on 11 Nov 2008 #permalink

Not mentioned is that corn is less and less "minimum cost." Since the big Republican led drive for ethanol addition to fuels, the demand for corn (and thus its price) has been rising steadily. This is not only bad for motorists (lower gas mileage), it has also resulted in continuously rising prices for all meats and poultry and many other foods as well.

Becca, my guess is that it has to do with the exact ratios. If they're using N ratios, they're probably using stable isotope ratios, which change with each step up the food chain. (Hence the extremely well-known geochemist joke, "You are what you eat plus one per mil." What? You haven't heard it? *sigh*) So, basically, cows (and their fat) have a different ratio than the corn they eat.

They can actually use the same methods to determine what ancient people ate (or where modern people are getting most of their calories). They can even use it to pin down the origins of people--for example, the guy they found frozen in (I think) the Alps? They used isotopes in his teeth (I think it was teeth) to identify which nearby valley he grew up in.

Stable isotope chemistry is bloody fascinating, if you ask me :)

Well, I found this mind blowing. Could just skip the fast food run, and have some corn, with a side order of nitrogen.

Odd to think of all those meaty, beefy, fried things deriving so much life from a single crop.

I love you blog. Why don't I spend more time here? I blame the corn.

"So ubiquitous is corn that out of the 160 items of food bought in Wendy's outlets throughout the country, not a single one could be traced back to a different food source. "

Wait, the salads are fed with corn? And the baked potatoes? then again, maybe that just means no one has ever bought a salad from Wendy's (which i guess i could believe)

And not a single damn place served it on the cob.

Our local Awesome Burger Place (Ray's Hell Burger) uses grass-fed (or some non-corn fed type) beef and served it with corn on the cob (white or yellow) and a slice of watermelon last time I was there.

Time to go back for more. It's so good. Fresh ground, grass-fed beef burgers are hard to top.

Dr. Kate- so cool. Except the joke. That was... interesting.
But, darn it-I was hoping to sneak some samples into lab and figure out whether the fries were fit for vegetarian consumption.

Austin- no one has ever bought a salad from Wendy's and lived to tell the tale, but that is another matter.

Actually, lettuce is mostly water, and most of their salads have corn-fed corn-fried chicken on them.
Presumably the potato's margarine and sour cream could get corn in them (same as the beef).
However, I'm sure "160 items" did not include 160 different menu items- most likely the things you mentioned just weren't tested.

"However, I'm sure "160 items" did not include 160 different menu items- most likely the things you mentioned just weren't tested."

Becca nails it. The 160 items are the hamburger, chicken burger and fries ordered multiple times from multiple branches in multiple cities.

"King Corn" is a wonderful documentary about corn. Two friends (Ian Cheney & Curt Ellis) rented 1 acre of farmland in the state of Iowa and grew corn on it. They search out where their crop winds up. They had the carbon isotopes in their hair analyzed (yup, corn) and visit grocery stores to try and find processed food without corn in it. They found very little that didn't. Everything form the corn itself to the chopped up corn stalks and leaves are fed to livestock. High fructose corn syrup winds up in just about every baked good, every soft drink, breakfast cereals, processed meats, ... And it has been linked to the rising incidence of diabetes.

Rent it and watch. Very interesting stuff.

Docuramafilms (
ISBN 1-4229-0938-7

I heard an NPR story a couple of weeks ago about food chain dynamics...why does this matter to asked. Too much of out food is depended on fossil fuels to produce it. That too much is actually corn, which is grown with ALOT of fertilizer. That fertilizer is produced from fossil fuels.

Remember when plats could photosynthesize all they neededfrom good old fashioned sunlight, plus soil (which contains nutrients) and water.

Like our financial portfolios we need to diversify our plate portfolio. Over dependence of 1 main food item makes us vulnerable to catastrophes.

I have to add that the results are definitely interesting but I read this a couple years ago in Michael Pollen's Omnivore's Dilemma which I highly recommend by the way. The corn prices in the US are effected by ethanol but the primary reason is the changes to corn subsidies that were implemented by the Nixon Administration and the book goes into a lot of detail on why corn prices are cheap and how Cargill and Tyson etc control the prices (and make ALL the profit). The changes to the subsidy program only helped the big companies and they lobby heavily to keep it that way.

Some may be aware of claims by a US medical researcher (can't recall name) that corn syrup has triggered much of the West's obesity and diabetes explosions because of problems in metabolising the chemically altered products (thank you, Japanese chemists!) available only in the past 25 or so years.

By Tony Ashton (not verified) on 16 Nov 2008 #permalink

I just want to second the King Corn and Omnivore's Dilemma recommendations. Both of them were quite eyeopening. I had never realized that most of the corn that is grown in Iowa is not grown for human consumption. It's not that sweet corn that we buy on the roadside or at our local farmer's markets. This stuff being grown nowadays needs to be processed in order for humans to be able to consume it. As Pollan says the irony is that with all that corn being grown in Iowa ("fence row to fence row" thanks to Earl Butz) the typical Iowa farmer can't feed himself.

By Tim Looney (not verified) on 18 Nov 2008 #permalink

Yeah I believe the fructose in "high fructose corn syrup" causes all sorts of problems for our metabolism. Way worse than table sugar as far as the effect on our insulin and putting on weight.