A bit­ter or sour taste is an in­di­ca­tor of a food that is un­ripe, rot­ten or poi­so­nous to the human or­gan­ism. In gen­eral, we tend to­wards cau­tion and react ex­cep­tion­ally scep­ti­cally to new foods; our sense of taste is di­vided into good and bad from birth. 

Our per­cep­tion of taste, how­ever, is some­thing we need to learn. As well as bad food, cer­tain nu­tri­tion­ally valu­able tan­nins and sec­ondary phy­to­chem­i­cals also taste bit­ter. 

We learn, for ex­am­ple, to value grape­fruit and chard, al­though we would in­tu­itively re­ject them at the first taste. Sec­ondary phy­to­chem­i­cals – like the monoter­penes found in pep­per­mint or the sul­phides that give gar­lic and onions their typ­i­cal flavour – are also healthy. They pro­tect us from free rad­i­cals, sup­port our im­mune sys­tem in re­sist­ing path­o­genic germs and can even have an anti-can­cer and cho­les­terol-re­duc­ing ef­fect.

Fur­ther In­for­ma­tion

• Article "The science of taste"