Why One Funky Experience Can Put You Off A Single Food For Life

I've had food poisoning exactly twice. The first time was from a dubious hibachi seafood situation that left me crying into my toilet bowl. The second time was from a bad batch of salchipapas, a Peruvian/Colombian/Ecuadorian street food I scarfed down on the streets of Guayaquil. The latter was topped with a ketchup-mayo mixture that tasted rad at the time; unfortunately, the eight-hour bout of projectile gastric emissions put me off mayo completely. To this day, I can't do mayo unless it's cleverly tucked inside a sauce or casserole. And according to a recent study, my neurology might be to blame.

A report in Science Daily rehashed a study from the University of Sussex in which scientists tried to figure out why a negative experience with food—food poisoning, a horrible first date, et cetera—often leaves us unable to stomach the thought of eating that particular dish again. To find out, the researchers trained snails to associate sugar with a negative experience—a gentle tap on the head—and found the negative experiences were actually causing a switch in their little snail brains.

The "aversive training" caused the snails to avoid the sugar completely, even when they were hungry. And the switch wasn't just behavioral—the researchers discovered a neuronal mechanism that effectively reversed the snails' response to sugar. "There's a neuron in the snail's brain which normally suppresses the feeding circuit," researcher Dr. Ildiko Kemenes explained. "This is important, as the network is prone to becoming spontaneously activated, even in the absence of any food. By suppressing the feeding circuit, it ensures that the snail doesn't just eat everything and anything. But when sugar or other food stimulus is present, this neuron becomes inhibited so that feeding can commence." In other words, snails will usually scarf down sugar whether they're hungry or not.

"After the aversive training, we found that this neuron reverses its electrical response to sugar and becomes excited instead of inhibited by it," Kemenes said. "Effectively, a switch has been flipped in the brain which means the snail no longer eats the sugar when presented with it, because sugar now suppresses rather than activates feeding." And when the neuron was removed entirely from trained snails? Well, they went back to their sugary ways. In conclusion, I'd like to volunteer for the next round of studies. It'd be great to enjoy mayo again.