When the banana ripens that means that the starch has already turned into simple sugar and it is easier to digest. Although according to researches, the quantities of vitamins and minerals reduces as the banana ripens. That is why it should be stored in a refrigerator.
Japanese researchers discovered a very interesting fact about bananas. According to them as the banana ripens it produces more antioxidants and more anticancer properties. When the banana is fully riped with dark spots on the yellow skin it produces a substance called TNF (Tumor Necrosis Factor), a substance that can combat abnormal cells. The research also shows that the more darker spots it has the better the anti-cancer properties are. Moreover, a banana with yellow skin and dark spots is eight times more effective in boosting body’s immune system than the green skin banana.
Therefore, the best time to eat the banana is when it’s fully ripen. But if you suffer from type 2 diabetes or you want to avoid a fast increase of your blood sugar levels, you might want to consider eating a riped banana with nut butter – because the fat slows down the sugar absorption into your blood stream. Or you can consume the banana while it’s still green (level 3 or 4 in the pic)
source : positivemed.com