Meat, fish, poultry, and eggs as they are usually considered tamasic (influenced by ignorance) and are not sanctioned by either the scriptures or saints. Almost all Hindus avoid beef out of respect for the cow. In the Mahabharata - a seminal Hindu epic - one of its central characters, Bhishma, declares that no sacrifices can be made without butter. And, thus, cows became essential to the spiritual life of Hindus. Alcohol, tea and coffee are said to pollute one's consciousness, making the practice of meditation difficult. Mushrooms are thought to take on the quality of ignorance, while garlic and onions take on the quality of rajas (passion).