Spinach is highly nutritious, containing exceptionally high amounts of vitamin A, vitamin C, vitamin K, folate, calcium, and manganese. It is also considered to be a rich vegetarian source of iron. However, the iron found in spinach is not easily absorbed by the body, partly because absorption is inhibited by calcium and fiber. To increase the bioavailability of iron from spinach and other leafy greens, be sure to include a good amount of vitamin C in your meal (think tomatoes, peppers, apples, and other fruits). (See more spinach nutrition facts on Self.com.)