Hangovers are caused by the excessive intake of alcohol, and as many of you may know, alcohol causes dehydration within the body. Bananas, however, are rich source of potassium, which is crucial for water transfer within the body. When your hangover reaches a fever pitch, grab a banana and boost your potassium levels, so water can move through your body more efficiently. Bananas also provide an energy boost, which can help people get through those sluggish morning hours, and even reduce headache symptoms by improving blood pressure.