a recent study has proven that large amounts of bananas can cause colon cancer over time. a study was undertaken last week in which 30 people aged 23 to 57 diagnosed with colon cancer were found to have above-average amounts of potassium in their blood. they were asked, and 85% said they consumed up to three bananas every day. colon cancer can be extremely serious, accounting for 22% of all cancer deaths per year on average. so stop eating bananas if you value your health in years to come.