Citrus fruits include diverse types and contain various carotenoids and flavonoids, which may provide enhanced nutrients and beneficial nutraceuticals
in the human diet. Carotenoids are the primary pigments for characteristic yellow to red colors and organoleptic attractions in different citrus fruits, while anthocyanins, a subgroup of colored flavonoids, independently yield “blood” red flesh only in blood oranges. Lycopene is the carotenoid for pink to deep red flesh in some grapefruits and oranges. Most genes in the two pathways are cloned and characterized, and the regulatory genes and mechanisms are being gradually uncovered primarily through comparison of red-fleshed mutants with their progenitors. Such knowledge will greatly facilitate continued varietal improvement for these beneficial components. Dietetics of citrus fruits and juice has been studied from both nutritional and preventive medicinal perspectives, with emphasis on lycopene and anthocyanins due to the special red color and predominant content in popular red-fleshed cultivars. The benefits include higher quality and availability of nutrients, substantially improved health biomarkers for lipid profiles, lower risk of obesity and cardiovascular disease, and potential suppression of some cancers. Moderate regular consumption of 100 % orange juice and/or fresh citrus fruits should be encouraged to help individual children and adults meet the United States Department of Agriculture (USDA) daily recommendation for fruit intake and a healthy diet.