In Head Trip, PopSci explores the relationship between our brains, our senses, and the strange things that happen in between.
THE FIRST TIME I had cilantro, I sat in the car with my mother, eating tacos from her favorite spot. As I settled in and took my first bite, I was immediately disgusted and spit it out. After repeated insistence that her food tasted fine and a quick Google search, we deduced that the problem was the cilantro and that I was, sadly, someone to whom it tasted like soap—Dove Sensitive Skin Beauty Bar, to be specific.
“You must get that from yo’ daddy,” she said, laughing.
The dislike of cilantro is a commonly known food aversion, though it affects only a small section of the population. A 2012 study on young adults in Canada found that, generally, dislike of cilantro ranges between 3 and 21 percent of the population, with varying ethnocultural specificities. Nevertheless, my mama isn’t wrong. There’s a strong chance that I did inherit this distaste for cilantro from my father or someone else in my direct lineage. But before we get into the genetic variations, it’s essential to understand the difference between literal taste and the perception of flavor.
Taste, scientifically, covers only salt, sweet, sour, bitter, and umami, which are chemical cues picked up by the tongue, explains James N. Palmer, the director of the division of rhinology at the University of Pennsylvania’s School of Medicine. “Flavor is the combination of taste and smell,” he says. “So what people will call taste isn’t really taste: It’s flavor.”
Our food is broken down with our teeth and the enzymes in our saliva when we eat. Next, the chomped-up bits glide over our papillae, the thousands of little bumps on the tongue, the roof of the mouth, and the throat. Those bumps contain taste buds, which each have between 50 to 100 chemical receptors that identify the five tastes.
“We use our taste system simply to identify specific chemicals in our food,” says Kathryn Medler, a professor in the University of Buffalo’s biological sciences department. “There are things that we need in our diet, so we prefer them. We eat things that are sweet, salty, or umami [because] those are [nutrients] that we need in our diet in order to be healthy. And we innately avoid sour things, which are going to potentially identify spoiled foods, as well as bitter, which are going to identify potential toxins.” (The cool thing about your taste buds, however, is that you can train them to acquire a taste for sour and bitter flavors.)
The chewing process also releases odorants. These smells travel up the back of the nasopharynx and into the back part of the nose, resulting in retronasal olfaction, which is how we process odors while consuming food. As we chew, our brains combine these signals to determine the flavor of a food or drink. (Our brains also pick up on mouthfeel–like stringiness or crispiness–as we chew, but that is a separate sensory process.) For instance, Palmer says that steak sauce and chocolate have the same levels of bitterness, sour, and sweet, and that it’s our sense of smell that makes us perceive them as different flavors.
Once the distinction between taste and flavor is clear, it’s easier to understand how DNA affects how we enjoy—or don’t enjoy—certain foods. Our genes influence how we experience flavor, not taste itself. Cilantro will always have a fresh, citrusy smell. But due to a variation in a cluster of olfactory receptor genes that makes them more sensitive to the scents of aldehyde chemicals—found in cilantro and used in soap making—eating cilantro can feel like chewing on a sudsy washrag to some people because the scent of aldehyde is released during chewing.
There are other factors—such as the foods we grew up eating—at play when it comes to why we love or hate certain tastes and flavors.
Most taste preferences and differences are not necessarily related to genes, says Medler; some can also be related to the cultures or regions we were raised or live in. Take okra, for instance. Medler and I both grew up eating fried okra because we’re Southerners, and we remain very fond of it because it reminds us of home. However, her husband, who grew up in New England, could take it or leave it. “It’s not that he inherently tasted something different than I tasted, but he doesn’t have the positive associations with it,” she explains.
But both Medler and I lose our affection for okra when it’s cooked in a way that makes it become slimy. The vegetable’s texture is crispier when it’s fried, because frying eliminates most of the gumminess. When it’s included in gumbo or the Nigerian soup obe ila, though, the slippery nature is more pronounced. Enjoying that mouthfeel is typically learned: A friend who grew up eating obe ila loves okra as a stew or fried—in part because it has positive associations for him and because he’s familiar with its textures.
Still, some food experiences, like my soapy-taco debacle, are genetically set in stone. “Everybody’s genetics are slightly different, which means their taste receptors are slightly different, which means [everyone is] going to have different powers in terms of tasting things,” says Palmer.
“I smile when my patients say, ‘Well, why do things taste different to me than they do to somebody else?’” he continues. “You’re a different height than everybody else. … You have all sorts of other genetic characteristics that differ. So you would expect taste genetics and smell genetics, and therefore flavor genetics, to be different for every person.”
Read more PopSci+ stories.