Citrus fruits. An assortment of citrus fruits: lemons (yellow, whole), grapefruits (yellow, cut), limes (green), kumquats (small, orange), clementines (medium, orange) and oranges. Citrus fruit is a good source of vitamin C or ascorbic acid. Vitamin C is needed for healthy blood vessels, bones and muscles. It also helps wounds to heal and is required for healthy gums.