1 Peppers have lots of beta-carotene; vitamins B6, C, and A; and potassium. 2  Potatoes, with skins, are a good source of protein, iron, vitamin C, and potassium. 3  Shallots are a good source of potassium, vitamin B6, manganese, and folic acid.4  Summer squash is high in vitamin C, fiber, potassium, and magnesium. Peppers have lots of beta-carotene; vitamins B6, C, and A; and potassium. 2  Potatoes, with skins, are a good source of protein, iron, vitamin C, and potassium. 3  Shallots are a good source of potassium, vitamin B6, manganese, and folic acid.