Nutrition and retina.

The impact of nutrition on manifestation and progression of retinal diseases has become an important, controversial topic within recent years. The awareness of this topic in the general population has increased partially due strong commercial advertisements of supplements and diets. However, many potentially beneficial nutritional effects on retinal diseases have not been proven in prospective clinical trials. It is only for a few relatively rare diseases, such as retinitis pigmentosa or gyrate atrophy, that adjustments in nutrition have been proven effective and widely accepted. However, for the majority of patients with retinal diseases the impact of nutritional factors is still insufficiently understood. Theoretically, supplementation of antioxidants could have a beneficial impact on a wide variety of retinal diseases or as a preventive measure by limiting the degree of oxidative damage. The only prospective, controlled, clinical trial providing proven benefit of antioxidant supplementation for a retinal disease is the Age-Related Eye Disease Study (AREDS). Patients with at least intermediate age-related macular degeneration (AMD) were shown to have a significant benefit with regard to disease progression by supplementing with high-dose antioxidants and zinc. It is however unclear whether other antioxidants, such as lutein or zeaxanthin, may be better and whether a preventive supplementation is useful. Especially studies on patients with diabetic retinopathy have implicated an impact of higher cholesterol levels on the progression of the disease. High-fat diets have been overall associated to a number of retinal diseases. With the current knowledge it seems prudent to advise everyone a balanced, low-fat diet as well as vitamin supplementation within the recommended daily allowance. Smoking is an essential factor for oxidative stress, and its cessation should be recommended to everybody in order to prevent or slow down progression of retinal disease. High-dose antioxidant supplementation according to the AREDS trial should currently only be recommended to non-smokers with at least intermediate AMD. Based on results from experimental studies, further prospective clinical studies are warranted on the prevention and inhibition of disease progression in the most common retinal diseases by nutritional means.