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Your nose could guide you to make more balanced eating decisions, according to a small new study.
When 30 participants ate cinnamon rolls or pizza, the researchers found that they became less sensitive to these smells than when they were still hungry.
Anyone who has pinched their nose and ate a bite of food knows that their smell can influence the taste of something, but this new research suggests that the taste of something can also influence our sense of smell, drawing us to certain foods and us. keeping away from others.
Researchers suspect that’s how our brains make sure we don’t eat too much of the same thing – a possible adaptive strategy to optimize our search for food.
“If you think of our ancestors roaming the forest in search of food, they find and eat berries and are not so sensitive to the smell of berries anymore,” says neurologist Thorsten Kahnt of Northwestern University.
“But maybe they’re still sensitive to the smell of mushrooms, so this could theoretically help facilitate diversity in food and nutritional intake.”
Previous studies have found our subjective opinions about the pleasant smell of certain foods based on what we ate, but this study investigated whether hunger and fullness can affect our sensitivity to smells.
Only a few animal studies and one human study to date have explored this idea, which means there are a lot of unanswered questions.
Rodent research, for example, has shown that fasting can influence the activity level of the olfactory bulb, which processes odors in the brain.
Additionally, in 2019, two of the same authors of the new research found that sleep deprivation in humans can sharpen the odors of high-energy foods in the island cortex, part of the olfactory pathway that responds to stimuli. food related.
These results were preliminary, but they suggested that our appetite might influence our sensitivity to certain smells.
In the new study, the researchers presented 30 hungry participants in the lab, having fasted for at least six hours. Inside an MRI scanner, these volunteers were then presented with a series of 10 scents, all of which contained a mixture of two scents: one was a smell of pizza or cinnamon buns, and the another was the smell of pine or cedar.
The ratio of food to non-food in the scent mixes was different for each of the 10 samples, and participants determined which scent they thought was more dominant for each: pizza or pine, or cinnamon or cedar.
The volunteers were then fed a meal of pizza or cinnamon rolls before completing the task again from the MRI machine.
“Along with the first part of the experiment taking place in the MRI scanner, I was preparing the meal in another room,” says Laura Shanahan, Northwestern neurologist and first author of the study.
“We wanted everything to be fresh, ready and hot because we wanted the participant to eat as much as they could until they were very full.”
Participants were able to quickly identify smells with more purity (when one odor was clearly dominant). But when the flavor blend became more even, what participants ate in the lab seemed to have an impact on how they smelled.
Those who received a pizza meal, for example, were less likely to smell the pizza when mixed with pine. Meanwhile, those who had their fix of cinnamon buns were less likely to smell the baked goods when mixed with cedar.
Yet when these same participants were hungry earlier in the day, they could see the dominant odor much better.
For example, a hungry participant earlier in the day might have only needed half the scent to smell the pizza to perceive it as dominant for the pine. But later, when that same participant had eaten his fill of pizza, he might have needed 80% of the scent to smell the pizza to perceive it as dominant.
When examining the results of the MRI scanners, the researchers noticed a similar pattern occurring in the brain.
The scans revealed that different olfactory pathways are activated after a meal than before a meal. For example, after feasting on cinnamon buns, participants showed less “food” responses to that same sweet smell.
Unfortunately, MRI brain scans are limited in that they aren’t able to measure neural activity directly in the olfactory bulb – so we still don’t know where these changes in our sense of smell actually occur in the brain.
“We are tracking how this information is changed and how the changed information is used by the rest of the brain to make decisions about food intake,” Kahnt explains.
The study was published in PLOS Biology.
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