Why does flavored water taste sweet even without sugar? According to new research from Karolinska Institutet in Sweden, it’s because the brain processes certain smells as if they were actual tastes.
The study, published in Nature Communications, used brain imaging to explore how taste and smell signals interact. Researchers found that the brain’s taste cortex, an area called the insula, reacted to sweet- and savory-associated aromas in the same way it did to actual sweet or savory tastes.
“We saw that the taste cortex reacts to taste-associated aromas as if they were real tastes,” said lead author Putu Agus Khorisantono. “The finding provides a possible explanation for why we sometimes experience taste from smell alone, for example in flavoured waters. This underscores how strongly odours and tastes work together to make food pleasurable, potentially inducing craving and encouraging overeating of certain foods.”
The team studied 25 healthy adults, teaching them to recognize both sweet and savory flavors. Participants then underwent fMRI scans while being given either a pure aroma or a taste without smell. The same brain patterns appeared when the participants smelled a taste-associated aroma as when they actually tasted food.
“This shows that the brain does not process taste and smell separately, but rather creates a joint representation of the flavour experience in the taste cortex,” said last author Janina Seubert, senior researcher at Karolinska Institutet. “This mechanism may be relevant for how our taste preferences and eating habits are formed and influenced.”
The researchers now want to see if this extends to external smells, like those we encounter in everyday environments.
“We want to find out whether the activation pattern in the brain’s taste cortex changes from salty to sweet when we walk from the cheese aisle to the pastries in the supermarket,” Khorisantono said. “If so, this could have a significant impact on the foods we choose to consume.”
The findings suggest that smell may play a bigger role in cravings, appetite and overeating than previously thought, offering new insights into how food environments shape our choices.
This research was funded by the European Research Council (ERC) and the Swedish Research Council.