New research published in the journal PLoS Biology has revealed that we are less likely to perceive smells of foods that we have recently eaten. These findings show that just as smell regulates what we eat, what we eat also regulates our sense of smell.
A team of scientists from Northwestern University developed a behavioral task in which participants were presented with a smell that was a mixture of food and non-food odors (such as pizza and pine), with the ratio of food to non-food odor varying in each mixture.
After a scent was presented, the participants were asked whether the food or non-food smell was dominant. This task was completed both before and after participants ate a meal matching one of the food odors.
The researchers found that if participants had just eaten, they needed a much higher percentage of food odor in a mixture to perceive it as dominant compared to when they were hungry. This proves that people are less sensitive to smells of foods that they have recently eaten.
Feedback between our olfactory system and food intake might have important evolutionary benefits, according to study senior author Thorsten Kahnt, an assistant professor in Northwestern University’s Feinberg School of Medicine.
“If you think about our ancestors roaming the forest trying to find food, they find and eat berries and then aren’t as sensitive to the smell of berries anymore,” said Professor Kahnt. “But maybe they’re still sensitive to the smell of mushrooms, so it could theoretically help facilitate diversity in food and nutrient intake.”
Thus, the olfactory sense might be very important for a balanced and diverse diet, and consequently for physical and psychological well-being, as researchers from Dr. Kahnt’s lab argue. If the feedback loop between the sense of smell and prior food intake is disrupted, problems such as disordered eating and obesity often emerge. Further research is needed to fully understand the complexity of our olfactory system, as well as its impact on physical and mental health.
Professor Kahnt said that with a better understanding of the feedback loop between smell and food intake, he’s hoping to take the project full circle back to sleep deprivation to see if lack of sleep may impair the loop in some way. He noted that with brain imaging, there are more questions about how the adaptation may impact sensory and decision-making circuits in the brain.
“After the meal, the olfactory cortex didn’t represent meal-matched food odors as much as food anymore, so the adaptation seems to be happening relatively early on in processing,” said Professor Kahnt. “We’re following up on how that information is changed and how the altered information is used by the rest of the brain to make decisions about food intake.”