A new study found that among people with a genetic susceptibility to age-related macular degeneration (AMD), those who ate more zinc, beta-carotene, lutein/zeaxanthin and the omega-3 eicospaentaenoic acid (EPA) and docosahexaenoic acid (DHA) cut their risk of developing the condition by up to a third compared with those who ate less of these nutrients.
AMD gradually destroys sharp, central vision that is needed for seeing objects clearly and for common daily tasks such as reading and driving. It affects the macula, the part of the eye that allows seeing fine detail. It is located in the centre of theretina, the light-sensitive tissue at the back of the eye. The retina is comprised largely of DHA, a dietary omega-3 fatty acid found mainly in fish.
AMD is the leading cause of blindness in developing countries and accounts for over 50% of blindness1. Approximately 2.5 million elderly people are affected by late AMD in Europe and 21 million worldwide1. In the United States, cases of AMD are expected to rise by about 50% over the next decade to reach 30 million by 20202. While the pathogenesis of AMD remains elusive, several risk factors have been established including age, smoking, atherosclerosis-like plaques associated with cardiovascular disease and certain genetic factors2 including the two gene variants CFHY402H that increases a person’s odds of AMD by 11-fold, and LOC387715 A69S that raises them by up to 15-fold. Together, these variants account for over 80% of AMD cases.
To date, there is no effective treatment for AMD and the only protective factors known for AMD are dietary nutrients. Previous population studies have shown that higher intake of fish and omega-3 long chain polyunsaturated fatty acids (LC-PUFAs) may reduce the incidence of advanced AMD, and that combinations of zinc, beta-carotene, Vitamin C & E reduce the risk of progression from intermediate to advanced AMD. However, up to now, few studies have investigated the impact of these nutrients on AMD in susceptible individuals. Given the public health importance of AMD, and the lack of successful treatment options, the results of this latest collaborative study from Eramus Medical Centre, Rotterdam, the Netherlands Institute for Neuroscience and the Academic Medical Centre, Amsterdam, The Netherlands, are encouraging.
The researchers studied the eating habits of 2167 people over the age of 55 years who were at risk of developing AMD due to genetic traits. All had eye exams every 3 years for the next decade to determine the development of AMD. Among people who carried the CFHY402H variant, greater intakes of dietary zinc, beta-carotene, EPA/DHA and lutein/zeaxanthin were associated with a lower risk of AMD. For example, 39 out of 100 people who ate the lowest EPA/DHA (about 22 mg/day) developed AMD compared to 28/100 who ate the largest amount of EPA/DHA (268 mg/day). In people with the LOC387715 A69S variant, reduced risk of AMD was seen in people who ate larger amounts of zinc and EPA/DHA. In this case, 25% of people who ate 11.85 mg/day zinc development AMD compared to 33% of people who ate only 7.5 mg/day zinc. The researchers noted that these benefits could be achieved by eating the recommended daily allowance of these nutrients.
This study adds to the current knowledge base recently reviewed linking omega-3 intake to lower incidence of AMD, where the potential benefit of omega-3 fatty acid supplementation is supported by their role normal retinal physiology, their anti-inflammatory properties, and the putative role of inflammation in AMD2 However, since oxidative stress has a recognised role in the development of AMD, and omega-3 fatty acids are susceptible to oxidation, this may partially masked their benefit. Therefore, co-supplementation with anti-oxidants may be necessary to reap the full benefit. Currently a five year randomized, double-blind, placebo controlled clinical study including over 4000 people is underway to provide proof of that benefit (www.areds2.org).
Not included in the review, was the strongest observational evidence to date showing that increased intake of fish and fish derived omega-3 LC-PUFAs, significantly decreases the risk of developing AMD by up to 42 percent.3 That study included 38,022 women aged 45 years or older and initially free of AMD who were followed for over ten years.
Although results of randomised, controlled trials are still not available, these reports strongly indicate that DHA supplementation may prevent the onset and/or slow the progression of AMD and that combined with anti-oxidants may provide greater benefit.
- Ho L, van Leeuwen R, Witteman J, van Duijn C, Uitterlinden A et al. Reducing the genetic risk of age-related macular degeneration with dietary anti-oxidants, zinc and omega-3 fatty acids. Arch Ophthalmol 2001;129(6):758-766.
- Kishan AU, Modjtahedi BS, Martins EN, Modjtahedi SP, Morse LS. Lipids and Age-related Macular Degeneration. Survey of Ophthalmology 2011;56(3):195-213.
- Christen WG, Schaumberg DA, Glynn RJ, Buring JE. Dietary ω- 3 fatty acid and fish intake and iincident age-related macular degeneration in women. Am J Clin Nutr Published ahead of print March 14, 2011, doi:10.1001/archophthalmol.2011.34.