Foods that contain the highest amounts of potassium are root crops, namely winter squash, sweet and white potatoes. Other potassium-rich foods include yogurt, broccoli and bananas.
Contrary to popular belief, bananas are not the richest source of potassium. One medium banana contains 422 milligrams of potassium, falling near the midpoint of the spectrum of potassium-rich foods. In comparison, some root crops contain twice as much potassium. One cup of cooked winter squash contains 896 milligrams of potassium. Sweet and white potatoes contain slightly less at 694 and 610 milligrams, respectively.
Some fruits still account for the some of the highest sources of potassium. An 8-ounce glass of 100 percent orange juice provides 496 milligrams of potassium and 1 cup of cubed cantaloupe adds 431 milligrams. On the other hand, one-half cup of white beans gives 595 milligrams of potassium and 1 cup of cooked broccoli contains 457 milligrams of the nutrient.
Fish and dairy products are also rich in potassium and specific types provide more of the nutrient than others. For example, a 3-ounce piece of Halibut contains 490 milligrams of potassium, whereas 3 ounces of canned tuna contains just 201 milligrams. Similarly, 1 cup of fat-free yogurt has 570 milligrams of potassium, whereas 8 ounces of low-fat milk contributes 366 milligrams.