Why do we eat? Study finds swallowing releases 'happy hormones', triggering desire for more food

Food is associated with happiness for many of us; no wonder there's something called stress eating. Now, a study on fruit flies found that there is a link between swallowing food and the release of happy hormones in the brain.

How do we humans distinguish between good and bad food? For most of us, our parents told us what to eat and what not to.But how do animals do the same process? Deciding what to eat, according to the researchers who conducted the fruit fly study, is "arguably the single-most salient decision that an animal has to make" as it's a critical part of survival in the wild.

That decision, it appears, is coded in the brains based on a reward system, or simply put, the release of happy hormones when good food goes through the gut.

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"We wanted to gain a detailed understanding of how the digestive system communicates with the brain when consuming food," says neuroscientist Michael Pankratz, from the University of Bonn in Germany, who was a researcher in the study. "In order to do this, we had to understand which neurons are involved in this flow of information and how they are triggered," he was quoted as saying in ScienceAlert.

The University of Bonn researchersexamined the larvaeof a fruit fly, or drosophila, to find out how swallowing affects the brain.For this, the scientists created 3D models of the larvaeafter slicing them down into thousands of small pieces and examining them under microscopes.

They identified a 'stretch receptor' in the esophagus of the larvaethat's linked to specific neurons in the brain of the fruit fly.

They found that some of these neurons play a role in detecting the quality of food and the happy hormone 'serotonin' is released when the food is good.

"[The neurons] can detect whether it is food or not and also evaluate its quality. They only produce serotonin if good quality food is detected, which in turn ensures that the larva continues to eat," ScienceAlert quoted neuroscientist Andreas Schoofs from the University of Bonn as saying.

This then triggers more desire for eating.

Fruit flies could be a good indicator, as their nervous system is simple and easier to study basic biological processes. Consider that these insects have only 200,000 neurons compared to 100 billion for us humans. They can thus be a scaled-down version of the human body.

The researchers seek to examine whether these same happy-hormone-releasing processes exist in other species too.

The gut is often called the second brain. While emotions will have an effect on our stomach, various ailments of the digestive system affect our moods and emotions too. One day, scientists will make sense of all this.

(With inputs from agencies)