A ray of light is shining directly on the carotenoid lutein, offering hope for improving visual function and preventing ocular diseases such as age-related macular degeneration (AMD) and cataracts. However, lutein may have to share its place in the sun. Zeaxanthin, lutein's rose-colored cousin, is also richly concentrated in the eye, but, unlike lutein, is far more elusive in the diet.

Both carotenoids seem to prefer residing in a region of the eye's retina called the macular pigment, made up almost exclusively of dietary lutein and zeaxanthin, with an even higher concentration of the latter. Zeaxanthin is abundant in spinach, lycii berry fruit (Lycium barbarum), the green algae spirulina and other types of commercially produced algae.

More studies are needed to conclusively determine if supplementation with zeaxanthin and/or lutein truly produces a functional improvement in vision and alters the course of AMD and/or cataracts.

Nutrition and exercise biochemist Anthony Almada, M.S. has collaborated on more than 45 university-based studies and is founder and chief scientific officer of IMAGINutrition.

Disclosure: Anthony Almada is a consultant to a producer of spirulina and a producer of an algae source of zeaxanthin.