According to Health.com, a medium orange contains 69.7 milligrams of vitamin C. In juice form, one cup of orange juice provides 97 milligrams of vitamin C, according to WebMD.
WebMD explains that vitamin C protects people from various health problems including heart disease, wrinkling of skin, eye disease and immune system problems. It also helps prevent serious complications that may arise from the common cold. For adults, the recommended daily allowance for vitamin C is 75 to 90 milligrams per day.
Aside from oranges, Health.com lists other good sources of vitamin C, including chili peppers, red and green bell peppers, kale, broccoli, papayas, strawberries, cauliflower and pineapple, among others.