Nutritional modulation of age-related macular degeneration

Abstract

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. It affects 30–50 million individuals and clinical hallmarks of AMD are observed in at least one third of persons over the age of 75 in industrialized countries (Gehrs et al., 2006). Costs associated with AMD are in excess of $340 billion US (American-Health-Assistance-Foundation, 2012). The majority of AMD patients in the United States are not eligible for clinical treatments (Biarnes et al., 2011; Klein et al., 2011). Preventive interventions through dietary modulation are attractive strategies because many studies suggest a benefit of micro and macronutrients with respect to AMD, as well as other age-related debilities, and with few, if any, adverse effects (Chiu, 2011). Preservation of vision would enhance quality of life for millions of elderly people, and alleviate the personal and public health financial burden of AMD (Frick et al., 2007; Wood et al., 2011). Observational studies indicate that maintaining adequate levels of omega-3 fatty acids (i.e. with 2 servings/wk of fish) or a low glycemic index diet may be particularly beneficial for early AMD and that higher levels of carotenoids may be protective, most probably, against neovascular AMD. Intervention trials are needed to better understand the full effect of these nutrients and/or combinations of nutrients on retinal health. Analyses that describe effects of a nutrient on onset and/or progress of AMD are valuable because they indicate the value of a nutrient to arrest AMD at the early stages. This comprehensive summary provides essential information about the value of nutrients with regard to diminishing risk for onset or progress of AMD and can serve as a guide until data from ongoing intervention trials are available.

Review of nutrient actions on age-related macular degeneration

“…Similarly, a significant synergistic interaction was described with regard to omega-3 fatty acids and dietary glycemic index; higher intake of omega-3 fatty acids (DHA and EPA) and low dietary glycemic index were associated with an even lower risk for advanced AMD compared to either of the two dietary factors alone [78]. In addition, recent studies on murine models also support these results [22,88].…”

“…However, current knowledge does not support the clinical use of supplements in patients with AMD. Several reviews have analyzed data obtained from case-controlled studies and randomized trials and have also found no evidence of supplements benefiting healthy people [22,35]. Evans and Lawrenson emphasized the clinical practice implications by stating: "there is no evidence from randomized controlled trials that healthy people should take antioxidant vitamin and mineral supplements to prevent or delay the onset of AMD."…”

“…In 2007, Robman and colleagues reported that increased intakes of dietary lutein, zeaxanthin, and omega-3 fatty acids were associated with AMD progression [21]. Subsequently, several studies reported the opposite results [22]. In particular, a recent study published by Ma et al reported that the intake of lutein and zeaxanthin supplements in patients with early AMD could improve the macular pigment optical density (MPOD) and visual function [23].…”

“…Data from the National Health and Nutrition Examination Survey, reported by Goldberg et al, showed a negative association between the frequency of fruit and vegetables rich in vitamin A consumed and the prevalence of AMD [16]. However, several subsequent studies and a large metaanalysis failed to confirm this association [20,22,39,40], and unexpectedly, one report even suggested an increased risk in the development of late AMD in participants who took vitamin A [41]. With these conflicting results, more research is needed regarding the association between vitamin A and AMD.…”

“…The glycemic index is a measure of the ability of 50 g of a specific food to increase blood glucose levels compared to the ability of 50 g of standard food to increase blood glucose levels [22,84]. Independent data support an effective role of a low dietary glycemic index in preventing the progression of AMD, particularly in people at risk for advanced AMD [78,[85][86][87].…”