What is the primary function of the spleen according to traditional theories?

The primary function of the spleen, according to traditional theories, revolves around its role in the movement and transformation of food. In Traditional Chinese Medicine (TCM), the spleen is viewed as essential for digestion, where it is responsible for extracting nutrients from food and converting them into Qi (vital energy) and blood. This process is critical because the quality of the nourishment obtained from food directly influences one's overall health and vitality.

The spleen is also thought to help in the transportation of nourishing substances throughout the body, ensuring that they reach various organs and tissues where they are needed. The health of the spleen is often linked with conditions such as fatigue, poor appetite, and digestive disorders, highlighting its foundational role in maintaining physical health.

In contrast, the other options reflect functions associated with different organs or systems within TCM. The storage of bile pertains more to the liver's role in the body, while heart protection aligns with functions attributed to different organs concerning emotional well-being. Regulating menstrual problems is typically associated with the functionalities of the kidneys and liver rather than the spleen. Thus, the focus on the spleen as governing the movement and transformation of food accurately encapsulates its primary function in the context of TCM.