A Starchy Sixth Sense Could Explain Why Humans Love Carbs

Our tongues may be even more sensitive than once thought

Family O'Abé via Flickr

Scientists had long thought that there were four taste elements: sweet, salty, sour and bitter. But in 2009, the savory taste sense known as Umami was added to the list. Now, a new study published in the journal Chemical Senses suggests it might be time to add a sixth taste sense to the human tongue, and it could explain our species' love for starchy foods, Jessica Hamzelou reports for the New Scientist.

While food cultures widely vary in their ingredients and tastes, there’s one element that is common to nearly all of them: starch. Derived from plants like yucca, wheat and rice, these carbohydrate-rich foods are common to cuisines around the world. Ethiopian food is often defined by injera, a sourdough-like pancake that is used as a utensil, while bread is so important to Syrian cuisine that aid groups have built their own bakeries to provide  refugees. Rice is the foundation of diets from East Asia to Spain, and of course it’s impossible to skip over the nearly-infinite varieties of pasta that people have created throughout human history.

Since starch is so essential, why have scientists only just now located this taste sense for carbs? Researchers previously believed that the flavors associated with these foods came from the sweet-sensing parts of our tongues, as complex carbohydrates are basically long chains of sugar molecules that start to break down as soon as they hit our saliva, Hamzelou writes. But for Juyun Lim, a food scientist at Oregon State University, this didn't track.

“Every culture has a major source of complex carbohydrate. The idea that we can’t taste what we’re eating doesn’t make sense,” Lim tells Hamzelou.

To test whether people might have a starchy taste sense, Lim and her colleagues gave 22 volunteers a taste of liquids with varying levels of carbohydrates dissolved into them. When she asked them to describe the liquid’s flavor, many responded by calling them “starchy,” Daisy Meager writes for Munchies. The participants continued to taste this starchy flavor even after they were given a chemical known to block the tongue’s sweet receptors, suggesting that they could sense the carbs independently of a sugary sensation.

“Asians would say it was rice-like, while Caucasians described it as bread-like or pasta-like,” Lim tells Hamzelou. “It’s like eating flour.”

Lim’s study used a small sample size and did not identify any particular parts of the tongue that could specifically sense starchy flavors. However, this does question previous ideas of how people taste complex carbohydrates. While more research needs to be done before researchers can say for sure whether or not starch should be enshrined alongside the five other tastes, it seems that there is a lot more to how our bodies sense flavors than scientists once thought.