Oct. 27, 2021 — Trick-or-treaters may not be so easily be tricked into loving sugar-free treats, thanks to taste buds hard-wired to seek calorie-containing sweets, a new study suggests.

Taste isn’t all about choosing peanut butter cups over jellybeans. Since earliest humanity, our sense of taste has helped us detect salty, sweet, sour, savory, and bitter so that we can choose foods high in energy and low in poisons.

But these new findings suggest that our taste buds have another hidden talent: identifying foods that don’t give us any energy at all.

Scientists suspected this ability after research in mice showed that their taste buds could distinguish between sugar and calorie-free artificial sweeteners.

To test this possibility in humans, scientists asked people to drink a series of clear beverages and identify whether they were plain water or sweetened. The goal was to compare how people responded to glucose — a natural caloric sweetener in fruits, honey, and table sugar — and sucralose, a calorie-free artificial sweetener.

All participants wore nose plugs, ensuring that they would use only their taste buds and not their sense of smell for detection.

As expected, people could easily tell plain water from sweetened drinks, whether with glucose or sucralose, confirming that taste buds detect sweetness.

In a twist, researchers then mixed in flavorless chemicals that block taste buds from picking up sweetness. With these drinks, people could no longer distinguish sucralose-sweetened beverages from plain water. But they could still tell when they had a beverage sweetened with glucose.

This finding indicates that two separate pathways underlie the mouth’s response to sugar, researchers report in PLOS One. The first pathway identifies sweet flavors, and the second one detects foods that contain energy that can be used for fuel.

Scientists might one day come up with calorie-free sweets that trick taste buds into detecting the presence of calories, enhancing their appeal. But in the lab studies, the participants had no visual cues or smell to guide their reactions, meaning how these other sensory inputs would affect treat perception isn’t known.