Headlines joked about cheese addiction, but the real science is far more complex
Cheese is a delicious invention. But if you saw the news last week, you might think it’s on its way to being classified as a Schedule II drug. Headlines proclaimed “Say cheese? All the time? Maybe you have an addiction,” “Cheese really is crack” and “Your cheese addiction is real.” Under the headlines, the stories referred to a study examining the addictive properties of various foods. Pizza was at the top. The reason? The addictive properties of cheese, which the articles claim contains “dangerous” opiate-like chemicals called casomorphins.
But you can’t explain away your affinity for cheese by saying you’re addicted. The study in those stories, published earlier this year in PLOS ONE, did investigate which foods are most associated with addictive-like eating behaviors. Pizza did come out on top in one experiment. But the scientists who did the research say this has little to do with the delicious dairy products involved. Instead, they argue, the foods we crave the most are those processed to have high levels of sugars and fat, and it’s these ingredients that leave us coming back for another slice. The cheese? Probably superfluous.
“I was horrified by the misstatements and the oversimplifications … and the statements about how it’s an excuse to overeat,” says Ashley Gearhardt of the University of Michigan in Ann Arbor, who led the study. “Liking is not the same as addiction. We like lots of things. I like hip-hop music and sunshine and my wiener dog, but I’m not addicted to her. I eat cheese every day. That’s doesn’t mean you’re addicted or it has addictive potential.”
Gearhardt and her colleagues set out to determine which foods are most closely associated with addictive-like eating behaviors. They recruited 120 undergraduates and another 384 participants from Amazon’s Mechanical Turk to take the Yale Food Addiction Scale. The survey is designed to identify signs of addictive behavior toward food and is based on similar criteria for drug addiction. The questionnaire asks participants to rank how often they overeat or eat more than intended, if they have persistently attempted to quit overeating certain foods and failed, and whether they have given up or reduced important social and recreational activities to pursue their drug — or food — of choice.
For the first experiment, the scientists gave the undergraduates choices between two different foods and asked them to select which of the items they were most likely to crave, binge on or come back to again and again. Selections included junk foods such as cookies, cake and pizza, as well as healthy options like broccoli, water and cucumber (tragically, with no dip). For each option they had to make a choice: Cookies or apples? Cheeseburgers or water?
In the second experiment, the Mechanical Turk participants weren’t asked to make a choice. Instead, they were asked to rate the same foods on a seven-point scale based on how likely they were to binge on or crave the foods, with one as not problematic, and seven as extremely problematic.
The most highly ranked foods — ones people were most likely to have problems with — were those that were highly processed, such as chips, cake and pizza. Foods low in carbohydrates, such as nuts and eggs, or those low in fat such as bananas and strawberries consistently ranked low. “When it comes to naturally occurring foods, even ones that people really like — apples, nuts, strawberries — people like them but they don’t lose control, they don’t have cravings,” says Gearhardt. “In contrast, when you look at highly processed foods, chocolate and pizza, those are the foods people struggle with.”
These foods are high in carbohydrates, salt and fat, Gearhardt explains. They have a high glycemic load, getting absorbed much more quickly by the body than eggs, nuts or granola bars. Quick absorption means a fast spike in blood sugar, which may, Gerhardt’s group hypothesizes, make these processed foods more likely to produce addictive-like behaviors. “What we think is important is that high glycemic load foods, foods that give intense rapid blood sugar spikes, were the most problematic,” she notes.
So where does cheese come in? And what about crack? The word “cheese” appears a total of five times in the study (nine, if you count “cheesecake” and “cheeseburger”). Words such as “crack” and “cocaine?” Only in the references.
When the researchers measured ranked how frequently a food was “problematic” for the participants, cheese wasn’t even in the top 10. It limped in at 16 out of 35, blown away by chocolate (number 1), french fries and pizza (numbers 3 and 4), buttered popcorn (number 8), and even gummy candy (number 12 — there’s no accounting for taste). When the second group was asked to rank foods on a scale of 1 to 7, cheese did a little better, at number 10. But again, it was outclassed by pizza, chocolate, chips, french fries and more.
And when it comes to sugars and other carbohydrates, cheese is a pretty dismal failure. “Cheese doesn’t have a high glycemic load at all,” Gearhardt explains. And when it comes to the number 1 craveability of pizza, she says, the cheese isn’t the issue. Instead, it’s the high carbohydrate levels in the crust and sauce. “Cheese on its own is not particularly problematic.”
But cheese and cocaine do have something in common other than both starting with the letter “c.” Cheese, like other foods, stimulates the reward system in the brain. “We know there are these areas of the brain, reward circuits involved in keeping us alive,” says Joseph Frascella, a neuroscientist at the National Institute on Drug Abuse in Bethesda, Md. “They are systems that signal to us when something we do is good, like eating, procreating or drinking water when you’re thirsty.” These systems are necessary to let us know what our bodies need and teach us to seek it out.
And these are the same systems in the brain that addictive drugs exploit. “Drugs of abuse hit these same pathways and they tend to do it much more effectively,” Frascella explains. “So you get that rush, that high, and the brain says, ‘wow that’s good for us, do it again.’”
But while cheese might be able to give you good feelings, when it comes to addictive properties, the cheddar cannot compare. “Addictive drugs do things that food doesn’t do that make them more addictive,” says Peter Kalivas, a neuroscientist at the Medical University of South Carolina in Charleston. “To put [those foods] on par with something like cocaine is pretty inflammatory.”
The coverage comparing cheese to crack focused on the role of casomorphins. These are small protein fragments that result from the breakdown of the milk protein casein. These fragments can bind to receptors for opioid molecules in the brain.
But “just because something activates your opioid system doesn’t make it addictive,” Gearhardt cautions. A 2009 scientific report on casomorphins from the European Food Safety Authority stated that it’s unknown whether these molecules escape from the gastrointestinal track in large amounts, or that they can get into the brain, though it is possible. When injected directly into animals, either into the body cavity or the brain, casomorphins did produce some effects such as pain relief and learning delays in newborn mice. But the peptide was also estimated to be 20 times less potent than morphine. In a 1994 dairy-funded study, rats were given casomorphin or morphine and placed in different chambers, allowing them to associate the drug with a particular chamber. After several days, researchers looked at which chamber the rats preferred to spend time in, a common test of the rewarding properties of drugs such as morphine. While the rats were glad to spend time in a chamber associated with morphine as compared to water, casomorphin produced no response.
“Understanding how food is rewarding and how it might overlap with addictive drugs is an interesting question,” Kalivas says. “Studies like this, to me, kind of state the obvious. Food that’s palatable, people will find more problematic.”
Claiming a cheese addiction based on this study? Nice try. The study itself does offer a chance to make people more aware of their eating habits, says Frascella. Knowing more about why we eat what we do can be a useful guide to eat more healthfully. But when it comes to cheese, there’s no need to worry. We can let the brie be.