The Ayurveda prescribes optimum proportions and measures for food, water, exercise to maintain health and improve resistance to diseases. The qualities and properties of different food groups come from their key components like minerals, vitamins etc, which should be taken in recommended amounts. Ayurvedic texts delineate properties and effects of various food items on the body as per their rasa or taste, guna or quality, virya or potency and vipaka or effect »» for creating balance in the three doshas, foods with opposing qualities should be included in the diet so that they could neutralize each other. If a substance has an aggravating action on one body while another property has a pacifying effect on it then the former is known as a virechana while the latter is known as a pachana.