According to Japanese Scientific Research, a fully ripe banana with dark patches on yellow skin produces a substance called TNF (Tumor Necrosis Factor) which has the ability to combat abnormal cells. The more darker patches it has, the higher its immunity enhancement will be; Hence, the riper the banana the better the anti–cancer quality. Yellow skin bananas with dark spots are 8 times more effective in enhancing the property of white blood cells than green skin versions.
It is a fact that the nutrient content of fruits changes slightly as they ripen. As a banana ripens and turns yellow, its levels of antioxidants increase. These antioxidants in ripe bananas protect your body against cancer and heart diseases. But while overripe bananas certainly have nutritional value, they also lose some benefits. In full ripe bananas with dark spots on skin, the starch content changes to simple sugars that are easier to digest higher in glycemic index
Tumor Necrosis Factor (TNF) is a cytokine, a substance secreted by certain cells of the immune system that communicate with other cells. They activate signaling pathways for cell survival, apoptosis, inflammatory responses, and cellular differentiation—all of which are used in fighting abnormal tumor cells in body. Research done on ripening bananas has proved that the levels of TNF induction increased markedly with dark spots on skin before the entire banana peel turned brown. The research concluded that the activity of the ripe bananas was comparable to that of Lentinan, a chemical immunostimulant that is intravenously administered as an anti–cancer agent. So, ripe bananas can act as an anti–cancer agents by stimulating the production of white blood cells.
Bananas also contain a few antioxidants which destroy free radicals. Free radicals are those molecules that ravage through the blood stream causing the formation of cancerous cells. By destroying free radicals, the antioxidants in bananas are able to minimise free radical damage in the body and fight cancer in its early stages.
Tips: Once bananas ripen fully, store them in the refrigerator to minimize further vitamin loss. Fresh bananas with brown patches on the skin are ripe enough to eat immediately. Make sure to avoid over–ripe bananas whose skin has turned brown or split open.