What term refers to the act of taking substances into the body for use?

The term that refers to the act of taking substances into the body for use is "ingest." This word specifically describes the process of consuming food, drinks, or any other substances through the mouth in order to allow the body to use those nutrients or compounds. Ingesting is the first step in the overall process of digestion and metabolism, where the substances are taken in and then subsequently broken down for absorption and utilization.

In contrast, terms like absorb, assimilate, and utilize describe different processes that occur after ingestion. Absorption pertains to the process of nutrients being taken across cell membranes into the bloodstream after ingestion. Assimilation then refers to the integration of these absorbed nutrients into the body’s cells for growth, repair, and energy. Finally, to utilize refers to how the body uses these nutrients for various functions, such as energy production or repair. Therefore, "ingest" is the most accurate description of the act of taking substances into the body.