Bitter/sweet symphony

Published April 24, 2020

Sweet foods don’t taste as good cold, but why is that? A UC Santa Barbara professor wanted to know, so — as biologist are wont to do — he turned to fruit flies. (They feel the same way about cold, sweet foods.) The flies’ neurons worked fine. The sugar molecules weren’t affected. So what’s up? Turns out the neurons that detect cold food are the ones that also detect hardness and bitterness. Put another way, when a fruitfly detects “cool” it’s really detecting “hard and bitter.” And that makes the food less appealing.
Bitter compounds trigger bitter neurons, which tell the fly to stop feeding. Hard foods trigger the mechanosensory neurons, which also tell the fly to stop feeding. And cool temperatures trigger both, to the same effect.