I've permanently gone off a food after getting sick while eating it — even if the food wasn't the cause

This is called 'conditioned taste aversion' — one of the most powerful and rapid forms of learning in mammals. A single pairing of a flavour with illness (even unrelated illness) creates a lasting negative association. It can form after just one exposure and last years. Evolutionary psychologists believe it evolved as a fast, reliable poison-avoidance system.