In Traditional Chinese Medicine (TCM), Fo Shou belongs to the 'Herbs that regulate Qi' category. Herbs in this category typically treat a TCM condition called 'Qi Stagnation'. Concretely it means that Qi is blocked in the body's Organs and Meridians, most typically the Stomach, Liver, and to a lesser extent, the Lungs. In modern medicine terms, Qi Stagnation often translates into psychological consequences such as depression, irritability or mood swings. It's also frequently associated with conditions such as premenstrual syndrome (PMS), menopausal symptoms, the development of breast swellings as well as various digestive disorders.
Furthermore Fo Shou is Warm in nature. This means that Fo Shou tends to help people who have too much 'Cold' in their body, although with less effect than a plant that would be Hot in nature. Balance between Yin and Yang is a key health concept in TCM. Those who have too much Cold in their body are said to either have a Yin Excess (because Yin is Cold in nature) or a Yang Deficiency (Yang is Hot in Nature). Depending on your condition Fo Shou can help restore a harmonious balance between Yin and Yang.
Fo Shou also tastes Bitter, Pungent and Sour. The so-called 'Five Phases' theory in Chinese Medicine states that the taste of TCM ingredients is a key determinant of their action in the body. Bitter ingredients like Fo Shou tends to have a cleansing action on the body by clearing Heat, drying Dampness and promoting elimination via urination or bowel movements. On the other hand Pungent ingredients tend to promote the circulations of Qi and Body Fluids. That's why for instance someone tends to sweat a lot when they eat spicy/pungent food. Lastly Sour ingredients help with digestion and restrain abnormal discharges of Fluids from the body, such as diarrhea or heavy sweating.
The tastes of ingredients in TCM also determine what Organs and Meridians they target. As such Fo Shou is thought to target the Spleen, the Stomach, the Liver and the Lung. In TCM the Spleen assists with digestion, Blood coagulation and Fluids metabolism in the body. The Stomach on the other hand is responsible for receiving and ripening ingested food and fluids. It is also tasked with descending the digested elements downwards to the Small Intestine. The Liver is often referred as the body's "general" because it is in charge of regulating the movements of Qi and the Body Fluids. It also takes a leading role in balancing our emotions. In addition to performing respiration, the Lungs are thought in TCM to be a key part of the production chain for Qi and the Body Fluids that nourish the body.