Bananas are mainly composed of carbs. Unripe bananas may contain decent amounts of resistant starch, which functions like fiber, aiding your gut and promoting healthy blood sugar levels. Bananas contain a number of vitamins and minerals in decent amounts. These include potassium and vitamins B6 and C. Like other fruits, bananas contain several healthy antioxidants, which are responsible for many of their health benefits. These include dopamine and catechin.