Age-related macular degeneration and its possible prevention

To the Editor: I read Constable’s article1 on age-related macular degeneration with interest, but was surprised at its somewhat guarded advice on nutritional supplementation and the fact that it gave only passing reference to uncontrolled studies of the carotenoids lutein and zeaxanthin and failed to mention a number of controlled studies that have recently shed light on the potential for these nutrients to influence the progression of age-related macular degeneration (ARMD).

Lutein and its isomer, zeaxanthin, are deposited in the macula, where they make up the macular pigments and act as a blue-light filter to protect the underlying tissues from phototoxic damage, as well as providing antioxidant activity. Lutein was not available in supplement form at the time of conducting the Age-Related Eye Disease Study (AREDS).2 However, the more recent Lutein Antioxidant Supplementation Trial (LAST), a double-masked, placebo-controlled, randomised trial of lutein and antioxidant supplementation in people with ARMD, demonstrated that taking 10 mg lutein daily, with or without additional nutrients, improved visual function.3 Interestingly, lutein supplementation was also found to improve vision in a small, randomised, placebo-controlled study of people with cataracts. It was suggested that these improvements were due to improved macular function and increased macular pigment density.4 Furthermore, a recent study showed that lutein supplementation results in increased macular pigment density in both normal and ARMD patients.5

Lutein occurs naturally in foods such as eggs, spinach, romaine (cos) lettuce, broccoli, zucchini, corn, peas and Brussels sprouts. Although lutein is readily absorbed from foods and dietary supplements, surveys indicate that average lutein intake may be below levels that are associated with disease prevention.6 Toxicology studies have established that lutein is generally safe, with potential for use as a supplement in foods and beverages.6

While advice on smoking cessation and increasing fruit and vegetable intake is useful for a wide range of conditions, including ARMD, Constable’s statement that “antioxidant supplements should be recommended if a fresh diet is impractical and if retinal signs of progression are present”1 appears overly cautious. In light of recent findings on the potential benefits of antioxidants such as lutein, and the low cost and minimal risks associated with supplementation compared with the potentially devastating consequences of blindness from ARMD, it may be prudent to make more general recommendations on nutritional supplements, rather than waiting until signs of retinal progression are evident.