My kids won't touch a banana that looks like this. But as an adult, eating bananas with dark patches can help fight cancer. According to Japanese Scientific Research, full ripe bananas with dark patches on the skin produce a substance called TNF (Tumor Necrosis Factor) which has the ability to combat abnormal cells. The more dark patches it has, the higher its immunity enhancement quality. So the riper the banana, the better the anti-cancer quality.