Sensory information from taste cells is critical for helping us to detect and respond appropriately to needed nutrients. The sweet taste of sugars, for example, provides a strong impetus for the ingestion of carbohydrates. Taste signals also evoke physiological responses, such as the release of insulin, that aid in preparing the body to use the nutrients effectively. Humans and other animals with a sodium deficiency will seek out and ingest sources of sodium. Evidence also indicates that people and animals with dietary deficiencies will eat foods high in certain vitamins and minerals.
Just as important as ingesting the appropriate nutrients is not ingesting harmful substances. The universal avoidance of intensely bitter molecules shows a strong link between taste and disgust. Toxic compounds, such as strychnine and other common plant alkaloids, often have a strong bitter taste. In fact, many plants have evolved such compounds as a protective mechanism against foraging animals. The sour taste of spoiled foods also contributes to their avoidance. All animals, including humans, generally reject acids and bitter-tasting substances at all but the weakest concentrations.