Many foods contain potassium, but it is found in greatest quantity in unprocessed foods such as fresh fruits and vegetables, whole grains, and fresh meats and dairy products. These same foods have the added benefit of being low in sodium. Many people think of bananas when they think of potassium, and for good reason. One medium banana packs 450 mg. And don't overlook the common bean.
Potassium is water soluble, so leaches into water during cooking.
A boiled potato, for example, loses at least half its potassium to the water it's boiled in. To reduce this loss, try steaming, microwaving, sauteing or even frying vegetables instead of boiling them. Keep the cooking water and add it to soups, stews and casseroles to increase their potassium content. Deficiencies of potassium are not common, but can result from excessive losses through prolonged vomiting, chronic diarrhea and laxative abuse. In extreme cases, potassium loss can cause heart failure and death.