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Mediterranean diet significantly reduces risk of AMD
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Adherence to a Mediterranean diet is associated with a significantly reduced risk of age-related macular degeneration, according to a study published in Ophthalmology.
The authors noted that other epidemiologic studies showed a reduced risk of AMD in diets with higher consumption of antioxidants and omega-3 polyunsaturated fatty acids.
The Mediterranean diet (MeDi) typically consists of plant foods, fish, olive oil as the primary fat source, moderate consumption of wine and low consumption of meat and dairy products. Therefore, researchers resolved to study associations between MeDi and the incidence of advanced AMD in two population-based prospective studies.
“Visual impairment resulting from AMD could influence dietary practices; prospective studies, by assessing diet prior [to] the onset of the disease, limit reverse causation,” the authors wrote. “Thus, a prospective design is more accurate and less biased than a cross-sectional or case-control design to evaluate the association between diet and AMD.”
Collaborators used the data from the Rotterdam Study I and Antioxydants, Lipides Essentiels, Nutrition et Maladies Oculaires (Alienor) Study populations. They analyzed data taken every 5 years for 21 years in 4,446 patients 55 years or older during the Rotterdam Study I (RS-I). Five hundred and fifty French patients were studied every 2 years during a 4-year period during the Alienor Study.
At each visit, patients in both studies were evaluated and graded for AMD using retinal photographs, turned in at-home checklists for MeDi adherence and completed face-to-face interviews with trained dieticians.
Researchers found that after pooling the data from both the RS-I and Alienor studies, individuals committing to higher adherence to the MeDi presented with a 41% lower risk of incident advanced AMD. These results suggested that an energy-unrestricted diet consisting of fruits, vegetables, legumes and fish as well as reducing intake of red, processed meat and savory industrialized products may assist in the prevention of AMD.
“Our results thus support public health efforts to emphasize adherence to the MeDi for everyone,” the authors wrote. “The biological basis for the potential benefits of the MeDi is associated with a decrease in oxidative stress and inflammation, which are also involved in the pathophysiology of AMD.” – by Scott Buzby
Disclosure: Merle reports that she is a consultant for Bausch & Lomb. Please see the full study for all other authors’ financial disclosures.
Perspective
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Richard Trevino, OD, FAAO
This prospective observational study found that Europeans age 55 years or older with no or early AMD at baseline had a significantly lower incidence of advanced AMD over 20 years of follow-up if they closely adhered to a Mediterranean-style diet compared to similar individuals who did not adhere to such a diet. These findings are consistent with a large and growing body of evidence that the Mediterranean-style diet has important health benefits, including reductions in cardiovascular disease, cancer and mortality (Estruch et al., Knopman). It has also been found to be protective against diabetic retinopathy in people with type 2 diabetes (Diaz-Ĺopez et al.).
A Mediterranean diet is one that is high in plant foods (such as fruits, nuts, legumes and cereals) and fish, with olive oil as the primary source of fat and moderate intake of wine, as well as low intake of red meat and poultry. However, before we begin encouraging our patients to trade in their T-bone steaks for ahi tuna, a few cautionary points regarding this study need to be considered.
First, there was no effort made to modify the diet of participants in this study; therefore, it can be reasonably assumed that the dietary preferences of these individuals were longstanding. Hence, this study does not shed any light on what effect dietary changes at midlife may have on the subsequent development of advanced AMD.
Second, it is important to remember that association does not prove causation. Because a healthy diet is often part of an overall healthy lifestyle, the participants in this study who adhered to a Mediterranean diet may also have been engaging in other healthy behaviors that affected their AMD risk. Only a randomized controlled trial can truly establish causal influence.
Finally, the researchers found that only the incidence of advanced dry AMD (geographic atrophy) was significantly reduced by the Mediterranean-style diet, not the incidence of neovascular AMD. This reminds us that the Mediterranean diet is not a “silver bullet.” Dietary interventions should be part of a multifaceted approach to AMD risk reduction that includes smoking cessation, regular physical activity and sunlight protection, among other measures.
Despite these considerations, this research does provide support for clinicians to offer dietary advice to those patients with little or no clinical evidence of AMD who wish to lower their risk of developing vision-threatening disease. Bon appétit!
References:
Diaz-Ĺopez A, et al. Diabetes Care. 2015;doi: 10.2337/dc15-1117.
Estruch R, et al. N Engl J Med. 2018;doi:10.1056/NEJMoa1800389.
Knopman DS. JAMA. 2009;doi:10.1001/jama.2009.1149.
Singh N, et al. Asia-Pacific J Ophthalmol. 2011;doi:10.22608/APO.201741.
Willett WC, et al. Am J Clin Nutr. 1995;doi:10.1093/ajcn/61.6.1402S.
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