There’s a concept called “learned food aversion”, which is just a fancy way of saying when people eat something and get sick shortly afterwards, people tend to avoid that food in the future. It makes sense from a survival perspective. If our ancestors ate a berry that was poisonous, they’d stop eating that berry.

This can suck as well though. If you eat your favorite food and then get sick from something else, then you can naturally start to not like your favorite food any more.

As a result, when patients are about to start chemotherapy, doctors might give them something like root beer flavored candy. That way, cancer patients will associate being sick with root beer candy rather than whatever they had for lunch that day.