June 14, 2011 — High dietary intake of antioxidants is associated with a lower risk for early age-related macular degeneration (AMD) in genetically predisposed individuals, according to the results of a nested case-control study reported in the June issue of the Archives of Ophthalmology.
"Within the framework of the large population-based Rotterdam Study, we explored the relationship between a healthy diet, genetic risk, and early AMD," write Lintje Ho, MD, MPH, MSc, from the Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues from the Rotterdam Study. "We assessed the intake of antioxidants, zinc, and ω-3 fatty acids in daily foods, diagnosed the onset of early AMD during a lengthy follow-up, and investigated the risk-reducing effect of these nutrients in the various genotypes of CFH [complement factor H] Y402H and LOC387715 A69S."
The study cohort consisted of 2167 individuals 55 years or older who were at risk for AMD and who were enrolled in the population-based Rotterdam Study. At baseline, participants completed a semiquantitative food frequency questionnaire, and a specific assay was used to identify genetic variants.
Median follow-up duration was 8.6 years. Fundus photographs at 3 follow-up visits allowed detection of incident early AMD. Biological interaction between risk factors was identified with the synergy index. Among subgroups based on levels of nutrient intake and genotypes, the risk for early AMD was estimated with hazard ratios (HRs).
Incident early AMD occurred in 517 participants. There appeared to be a possible biological interaction between the CFH Y402H genotype and intakes of zinc, β-carotene, lutein/zeaxanthin, and eicosapentaenoic/docosahexaenoic acid (EPA/DHA), and between the LOC387715 A69S genotype and zinc and EPA/DHA, based on significant synergy indices (P < .05 for all).
Participants who were homozygous for CFH Y402H and had dietary zinc intake in the highest tertile had a reduction in HR for early AMD from 2.25 to 1.27. Similar risk reductions were observed intakes in the highest tertile for β-carotene, lutein/zeaxanthin, and EPA/DHA.
Among carriers of LOC387715 A69S, those in the highest tertile of zinc intake had a reduction in HR from 1.70 to 1.17; those in the highest tertile of EPA/DHA intake had a reduction in HR from 1.59 to 0.95 (all P trends < .05).
"High dietary intake of nutrients with antioxidant properties reduces the risk of early AMD in those at high genetic risk," the study authors write. "Therefore, clinicians should provide dietary advice to young susceptible individuals to postpone or prevent the vision-disabling consequences of AMD."
Limitations of this study include the relatively low number of cases in the stratified analyses, possible misclassification in the stratification of nutrient intakes, and confounding by other potentially protective lifestyle and dietary factors.
"Fortified cereals, meats, dairy products, nuts, and seeds are a good source of zinc; dark-green leafy vegetables such as spinach and kale and orange vegetables including carrots and pumpkin are rich in β-carotene and lutein/zeaxanthin; and oily fish such as herring, salmon, sardines, trout, and tuna provide EPA/DHA," the study authors conclude. "These nutrients are all recommended in the Food Guide Pyramid and should be part of a regular diet for older adults."
The Netherlands Organization for Scientific Research, the Hague; Optimix, Amsterdam, the Netherlands; Neyenburgh, Bunnik, the Netherlands; Physico Therapeutic Institute, Rotterdam, the Netherlands; Swart van Essen, Rotterdam; Blindenpenning, Amsterdam; Sint Laurens Institute, Rotterdam; Bevordering van Volkskracht, Rotterdam; Blindenhulp, the Hague; Rotterdamse Blindenbelangen Association, Rotterdam; OOG, the Hague; kfHein, Utrecht, the Netherlands; Prins Bernhard Cultuurfonds, Amsterdam; Van Leeuwen Van Lignac, Rotterdam; Algemene Nederlandse Vereniging ter Voorkoming van Blindheid, Doorn, the Netherlands; Oogfonds Nederland, Utrecht;MDFonds, Utrecht; Lijf en Leven, Krimpen aan de Ijssel, the Netherlands; and Topcon Europe BV, Capelle aan de Ijsse, the Netherlands, supported this study. The study authors have disclosed no relevant financial relationships.
Arch Ophthalmol. 2011;129:758-766. Full text
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