“The physiology of the human body is governed by three main forces, which are commonly known as the three doshas. Although dosha literally means faulty or to cause harm, they only do so when they are functioning abnormally. When functioning normally, they maintain the good health of the body and guide all the normal bodily processes.
Unlike the five elements, the three doshas are very real, albeit subtle, forces that exist within the body. They can not be measured in any real sense, but they can be observed and monitored.
In the physical body, the three doshas – vata, pitta and kapha – mirror the three basic functions of all existence. All of existence must come into creation. Once created, all of existence struggles for survival. Eventually, all of creation returns to dust for recycling. Kapha is the force behind all physical creation. Pitta is the force that struggles to maintain the creation and vata is the force that ultimately destroys creation…
Even though these functions are assigned to the doshas, it is a misconception to equate a kapha person as a creator, a pitta person as a preserver, or a vata person as a destroyer. Kapha energy creates only by building new tissues. Pitta maintains by regulating metabolism and vata destroys through the wear and tear of action and activity. Hence, creation, preservation and destruction define the roles of the doshas but not the psycho-spiritual nature of the person.”
~ Dr. Marc Halpern, from “Principles of Ayurvedic Medicine,” textbook for the Ayurvedic Profession.