Nutrition facts The nutrition facts for 1 medium-sized banana (100 grams) are (1Trusted Source): Calories: 89 Water: 75% Protein: 1.1 grams Carbs: 22.8 grams Sugar: 12.2 grams Fiber: 2.6 grams Fat: 0.3 grams Vitamins and minerals Bananas are a good source of several vitamins and minerals, especially potassium, vitamin B6, and vitamin C (1Trusted Source). Potassium. Bananas are a good source of potassium. A diet high in potassium can lower blood pressure in people with elevated levels and benefits heart health (6Trusted Source). Vitamin B6. Bananas are high in vitamin B6. One medium-sized banana can provide up to 33% of the Daily Value (DV) of this vitamin. Vitamin C. Like most fruit, bananas are a