Although we are all familiar with the potassium content of bananas, foods such as potatoes, spinach, and beans actually contain more potassium than fruit. Getting 2,000 to 4,000 mg of potassium a day can help lower blood pressure. The nutrient causes the kidneys to excrete more sodium in the urine. Other good sources include tomatoes, avocados, edamame, watermelon, and dried fruits.