What is the process of breaking down food into simpler chemical components for absorption called?

The process of breaking down food into simpler chemical components for absorption is called digestion. This intricate process starts in the mouth, where mechanical and enzymatic action begins to break down food, and continues in the stomach and intestines, where various enzymes and acids further digest the food. The goal of digestion is to reduce complex food molecules into simpler substances, such as amino acids, glucose, and fatty acids, so that they can be easily absorbed into the bloodstream for use by the body.

Metabolism refers to the complex biochemical processes that occur in the body to convert food into energy, including the processes that happen after digestion, but it does not specifically refer to the breakdown of food itself. Fermentation is a specific type of metabolic process where sugars are converted into acids, gases, or alcohol, usually in the absence of oxygen, and is not a general term for digestion. Assimilation follows digestion and metabolism; it's the process by which the nutrients absorbed from digestion are incorporated into the body’s tissues. Thus, digestion specifically covers the initial breakdown process, clarifying why it is the correct answer.