The grapefruit is a subtropical citrus tree grown for its bitter fruit. The fruit is yellow-orange skinned and largely oblate, and ranges in diameter from 10-15 cm. The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink and red pulps of varying sweetness. The family of flavors range from highly acidic and somewhat bitter to sweet and tart. Grapefruit is an excellent source of vitamin C, a vitamin that helps to support the immune system. Vitamin C-rich foods like grapefruit may help reduce cold symptoms or severity of cold symptoms.