Supplements may produce a feeling of wanting to throw up, and may be poisonous in some cases. The best sources of iron, and the only sources of the form of iron most readily absorbed by the body, are meat, chicken, and fish. Good sources of other forms of iron include dates, beans, and some leafy green vegetables. "Select breads and cereals with the words 'iron-added' on the label," writes sports diet expert Nancy Clark. "This added iron supplements the small amount that naturally occurs in grains. Eat these foods with plentiful Vitamin C for example, drink orange juice with cereal or put a tomato on a sandwich to enhance the amount of iron absorbed."