In Samkhya philosophy there are three major guṇas which serve as the fundamental operating principles or "tendencies" of prakrti (universal nature) which are called: sattva guṇa, and rajas guṇa, tamas guṇa. The three primary gunas are generally accepted to be associated with creation (satva), preservation (rajas), and destruction (tamas). The entire creation and its process of evolution is carried out by these three major gunas.All material nature is made up the interplay of three energies or "gunas". Part of the work of yoga is to go beyond the limitation of seeing life as forms and concepts, and to see the underlying qualities of things. The gunas are a great map for navigating your way through life. When you can recognize which of these energies is at play in your life, it makes it so much easier to bring about a state of balance.
Sattva is a calm, peaceful and clear energy. The Sanskrit word is based on the principle "Sat" or "being, as it should be, perfect."
Generally: is a passionate, frenetic, creative, tumultuous energy.
Food that is Rajasic is quite stimulating (often times over stimulating). Eg: spicy, sour, acid foods like coffee, hot peppers, onions and so on. If you find yourself eating really quickly too, this too can be rajasic. If you have ever been to a big smorgasbord and eaten way too many combinations of food, you would have belly will be feeling the effect of Rajas Guna
Tamas is dull, insensible, gloomy and dark energy. The Sanskrit word literally means "darkness, dark-blue, black"
Food: that is Tamasic is stale, under or over ripe. Heavy meats. Canned, reheated or fermented foods. Eating too much is Tamasic.