In the unmanifested Universe, energy has three qualities, known as Gunas, that exist together in equilibrium: Sattva (purity, goodness); Rajas (activity, passion, the process of change); and Tamas (darkness, ignorance, inertia). Once energy takes form, one quality of the three predominates. Thus on an apple tree, some of the fruit is ripe (sattvic), some ripening (rajasic) and some overripe (tamasic). But no matter which quality prevails, an element of each of the other two will always be present as well. Most of an individual apple will be ripe, but part will be rotten, even if the naked eye cannot see it, and part will be in the process of changing from one state to the other. The three Gunas encompass all existence, all actions. If a man commits a robbery, the action is basically rajasic but the decision to rob and the motive may be predominantly tamasic, rajasic or sattvic, according to the situation. In all people one of the three Gunas has superior strength and is reflected in all they do and think. Only in enlightenment are the Gunas completely transcended.
The Gunas can be found in all beings and objects surrounding us. The Yoga aspirant always exerts to increase Sattva in his/her lifestyle. One of the most dramatic changes that can be made is adjusting our diet. The Yogic system of nutrition recognizes three types of food:
Sattvic Food
This is the purest diet, the most suitable one for any serious student of yoga. It nourishes the body and maintains it in a peaceful state. And it calms and purifies the mind, enabling it to function at its maximum potential. A sattvic diet thus leads to true health: a peaceful mind in control of a fit body, with a balanced flow of energy between them. Sattvic foods include cereals, wholemeal bread, fresh fruit and vegetables, pure fruit juices, milk, butter and cheese, legumes, nuts, seeds, sprouted seeds, honey, and herb teas.
Rajasic Food
Foods that are very hot, bitter, sour, dry, or salty are rajasic. They destroy the mind-body equilibrium, feeding the body at the expense of the mind. Too much rajasic food will overstimulate the body and excite the passions, making the mind restless and uncontrollable. Rajasic foods include hot substances, such as sharp spices or strong herbs, stimulants, like coffee and tea, fish, eggs, salt and chocolate. Eating in a hurry is also considered rajasic.
Tamasic Food
A tamasic diet benefits neither the mind nor the body. Prana, or energy, is withdrawn, powers of reasoning become clouded and a sense of inertia sets in. The body's resistance to disease is destroyed and the mind filled with dark emotions, such as anger and greed. Tamasic items include meat, alcohol, tobacco, onions, garlic, fermented foods, such as vinegar, and stale or overripe substances. Overeating is also regarded as tamasic.