Let me guess! This what you are doing whenever you have ripe bananas. You let it ripe to the fullest until you can see numerous brown spots on peel surface. You believe, the more spots it has the more anti-cancer properties it possess. Why is that? Because you saw it on you favorite wall!
I did few days of intermittent reading about it and found out all different posts and claims point to results of Japanese researchers Haruyo Iwasawa and Masatoshi YamazaKi:
Differences in Biological Response Modifier-like Activities According to the Strain and Maturity of Bananas
There are no conclusive facts that it fight cancer. Yes it has antioxidant substances that increase as it ripen. But, those are not necessarily and specifically anti-cancer. Their conclusion was broad and suggestive. They didn’t even mention it in discussion of results.
In Introduction – phytochemicals have been shown to play various roles in protecting the body from diseases — anti-oxidative, anti-inflammatory anti-allergic and anti-cancer effects.
I’m sure all fruits and vegetables have phytochemicals. So if eating overripe bananas can help you fight cancer and other diseases, then others can do the same too.
In my opinion. It is okay to let bananas go overripe but don’t let it go to the point of near spoilage. Start eating a hand when it is ready and you’ll find some are overripe before end. Start eating a hand when overripe and you’ll be forced to consume it all in one go.
update: Eating Overripe Bananas