Turnips are a good low calorie source of vitamin C and fiber. Turnip greens contain large amounts of vitamin A and especially large amounts of lutein, which has been shown to help prevent cataracts and cardiovascular disease. Turnips have been unfairly singled out as an unpleasant vegetable, when in reality their taste is similar to radishes when raw, and very mild once cooked.Turnips also contain more familiar nutrients such as fiber, vitamin C, vitamin B6, folate, calcium, potassium and copper.