CHAPTER 7: Egg Carotenoids for Eye Health

The center of the human retina contains a high concentration of two carotenoids, lutein (L) and zeaxanthin (Z). This region of the retina is called the macula and is important for high visual acuity. The carotenoids in the macula are abundant in the yolk of chicken eggs when the chickens are fed a diet enriched in corn and the lipid matrix of the egg yolk provides enhanced bioavailability. A 1 mg dose of L and Z from eggs is about 4× more readily absorbed from the diet than 1 mg from a plant source, such as spinach. This evidence supports the hypothesis that diets with frequent egg consumption are an excellent dietary source of L + Z. The best-established function of L + Z in the macula is to improve central visual acuity by reduction of chromatic aberration caused by blue-wavelength light reaching the retina. L + Z may contribute to the prevention of age-related macular degeneration by protecting blue-light-sensitive photoreceptors. Diets that contain eggs rich in L + Z consistently increase plasma levels of L + Z and may increase macular pigment levels if provided for a long duration, typically several months. Epidemiological studies support these visual benefits of eggs; controlled intervention trials would provide the most compelling evidence.