They are based on the Anthahkarana, the inner consciousness. That too is dependent on the intake of food. He can promote Sathwic tendencies through planned self-effort. This advice was tendered lovingly by the Lord to the eager inquirer, Arjuna. Krishna showered grace through His enchanting smile and condescended to reply.
Food is the chief formative force.
The divine cannot be reflected in the wicked or vicious mind. Strength of mind depends upon strength of body too. Food to be Sathwic should be capable of strengthening the mind as well as the body. It should not be too salty, too hot, too bitter, too sweet or too sour. It should not be taken while steaming hot.