New research reveals that a meal can trigger reward signals in the brain twice: first when the food is ingested and again when the food reaches the stomach.
The study, published this week in the journal Cell Metabolism, highlights how close interactions between the brain and the digestive system are able to reinforce food intake, and might provide a clue as to why we sometimes overeat the food we crave most.
It’s well known that food can trigger the release of the ‘feel-good hormone’ dopamine in the brain. Moreover, studies in mice have shown that when food reaches the gut, it contributes to this overall dopamine ‘reward’. Yet, exactly how the human brain encodes a reward value for different foods is still not fully understood.
To get a better idea of what is going on specifically in the human brain when it comes to food intake, Marc Tittgemeyer and his colleagues at the Max Plank Institute for Metabolism Research in Germany set up a study in which 12 healthy volunteers were given either a nice tasting milkshake or a tasteless solution, while their brains were scanned via positron emission tomography (PET).
PET scanning enabled the researchers to monitor the release of dopamine, and in doing so, they discovered that dopamine is released at two distinct time points and in different parts of the brain.