It is a fish of the open water which can grow up to 400 cm in length. Tuna of the same species live in schools with their peers, and some species of tuna can live up to 30 years. A rare derivative of selenium called selenoneine, an extremely valuable antioxidant can be found in tuna. Selenium protects the red blood cells of tuna from damage and can also bind mercury accumulated in the fish’s body. Tuna is an excellent source of vitamin B3, B12 and B6 as well as protein. In addition to its phosphorous content it is rich in vitamin B1, B2, vitamin D and minerals like potassium, iodine and magnesium.