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.

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