Potassium
Why you need it: Potassium is an essential electrolyte, needed to control the electrical activity of the heart. It is also used to build proteins and muscle, and to break down carbohydrates into energy.
Where to get it: One medium-sized baked sweet potato contains nearly 700 mg of potassium. Tomato paste, beet greens, and regular potatoes are also good sources, as are red meat, chicken, and fish.