A diet that is wholly conducive to the practice of Yoga and spiritual progress is called Yogic diet. Diet has intimate connection with the mind. Mind is formed out of the subtlest portion of food. Sage Uddalaka instructs his son Svetaketu “Food, when consumed becomes threefold: the gross particles become excrement, the middling ones flesh and the fine ones the mind. My child, when curd is churned, its fine particles which rise upwards, form butter. Thus, my child, when food is consumed, the fine particles which rise upwards form the mind. Hence verily the mind is food.” Again you will find in the Chhandogya Upanishad: “By the purity of food one becomes purified in his inner nature; by the purification of his inner nature he verily gets memory of the Self; and by the attainment of the memory of the Self, all ties and attachments are severed.”
Diet is of three kinds Sattvic diet, Rajasic diet and Tamasic diet. Milk, barely, wheat, cereals, butter, cheese, tomatoes, honey, dates, fruits, almonds and sugar-candy are all Sattvic foodstuffs. They render the mind pure and calm. Fish, eggs, meat, salt, chillies and asafoetida are Rajasic foodstuffs. They excite passion. Beef, wine, garlic, onions and tobacco are Tamasic foodstuffs. They fill the mind with anger, darkness and inertia.