Black banana hearts are generally inedible. Black banana hearts may be caused by oxidation, mold or bacterial infection. Banana heart contains a lot of polyphenol oxidase, which can easily catalyze the reaction between the phenolic substances in bananas and oxygen, making the banana heart black. Although oxidized banana hearts are less harmful, it is generally not recommended to consume them. When banana hearts are infected by mold or bacteria, they will deteriorate and rot, thus becoming black. This situation can no longer be consumed, and eating it will irritate one’s intestines and stomach, inducing one’s digestive system to suffer from diseases. Banana is rich in dietary fiber and potassium, and many vitamins, eating it can enrich the nutrition of human body. Every 100 grams of banana contains 93 calories, of which 22.0 grams of carbohydrates, 1.4 grams of protein, 0.2 grams of fat, 1.2 grams of dietary fiber, 256 milligrams of potassium, vitamin C8 milligrams. However, people with digestive disorders and diabetics are not recommended to consume bananas in large quantities.