Various types of mushrooms, including shitake and maitake mushrooms, have shown them to be high in potassium content. Potassium acts as a vasodilator, relaxing tension in blood vessels and thereforereducing blood pressure. High blood pressure is connected to a number of deadly conditions, particularly heart attacks and strokes. Potassium alsoincreases cognitive function, because increased blood and oxygen flow to the brain stimulates neural activity. Studies have shown that increased levels of potassium improve memory and knowledge retention.