Have you ever wondered how ripe bananas should look like, that are best for your health? Here are the results of scientific research conducted in Japan. Fully ripe banana contains TNF, or tumor necrosis factor, a substance that has the ability to fight abnormal cells. Destroy Belly Fat In 2 Weeks With This 1 Weird Trick (Start Now) As bananas ripen, they develop dark spots on their peel. The more dark spots that have they are healthier. Bananas with dark stains contain more substances that will boost your immunity. Fully ripe banana is perfect for your digestive system because the sugar out of it easily absorbed unlike green bananas that is hard to digest because their hard starch into sugar. The most important thing is to always eat ripe banana with dark spots that is best for your health.