June 14/Rotterdam, The Netherlands/Internal Medicine News Digital Network -- High dietary intake of antioxidants, zinc and omega-3 fatty acids may reduce the risk of early age-related macular degeneration in patients with the high genetic risk, according to the findings of a prospective, population-based study in the June issue of Archives of Ophthalmology.

Studies have shown that some 80% of late age-related macular degeneration (AMD) cases are due to variants in the complement factor H (CFH) and LOC387715/HTRA1 genes. "To reduce the burden of this disease, it is therefore essential to find means to counteract these major gene effects," the researchers said. "The only protective factors for AMD known to date are nutrients."

With this in mind, Dr. Lintje Ho of Erasmus Medical Center, in Rotterdam, the Netherlands, and colleagues investigated whether antioxidant, zinc and omega-3 fatty acid intake from daily foods could reduce the risk of early AMD in patients with the various genotypes of CFH Y402H and LOC387715 A69S (Arch. Ophthalmol. 2011;129:758-66).

To do so, they analyzed a subset of patients from Rotterdam Study, a prospective, population-based cohort investigation of chronic diseases in residents aged 55 and older of a Rotterdam suburb. Subjects underwent a comprehensive eye examination at baseline (1990-1993) and at three follow-up visits (1993-1994, 1997-1999 and 2000-2004).

To be eligible, participants had no AMD during the entire study period or developed early AMD during follow-up. A total of 2,768 individuals were eligible for the study, and 2,167 individuals were included in the final analysis.

Of these subjects, 517 (24%) developed early AMD during a median follow-up period of 9 years. These patients were slightly older (mean age 68 years) than were those with no AMD (mean 66 years), fewer were diabetic (7% vs. 10%), and they had a higher frequency of CFH Y402H (62% vs. 55%) and LOC387715 A69S genotypes (41% vs. 33%).

Results showed significant interactions between the CFH Y402H genotype and intake of zinc, beta-carotene, lutein/zeaxanthin, and eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA). Specifically, dietary intake of zinc in the highest tertile reduced the hazard ratio for early AMD from 2.25 to 1.27. Hazard ratios were reduced from 2.54 to 1.47 for highest intakes of beta-carotene, 2.63 to 1.72 for lutein/zeaxanthin, and 1.97 to 1.30 for EPA/DHA.

Results also showed a significant interaction between LOC387715 A69S genotype and intake of zinc and EPA/DHA. Carriers with the highest intake of zinc reduced their risk from 1.70 to 1.17, while those with the highest intake of EPA/DHA reduced their risk from 1.59 to 0.95.

Dietary antioxidants may help counteract oxidative damage that can activate the complement system, which plays a role in the pathogenesis of AMD. For example, zinc may help reduce complement activation that is already underway. Also, omega-3 fatty acids help prevent inflammation in the retina, another factor in the pathogenesis of AMD, by lowering acute-phase proteins, including complement C4, immunoglobulin M (IgM), haptoglobin, C-reactive protein, and fibrinogen, the researchers say.

Individuals need only consume the recommended daily allowances rather than excessive amounts of these nutrients to benefit, the researchers said.

They recommend fortified cereals, meats, dairy products, nuts, and seeds as sources of zinc, dark green leafy vegetables and bright orange vegetables as sources of beta-carotene, and oily fish as a source of EPA and DHA.

The relatively low number of cases in the stratified analyses is a limitation, although the researchers said they still could identify clear trends of risk reduction.

The authors reported having no financial conflicts. This study was supported by the Netherlands Organization for Scientific Research, among other sources.

 

From the June 15, 2011, Prepared Foods' Daily News.