Findings from this study suggest that fatty acid intake may correlate to AMD, although research on a more diverse population are needed. Photo: Getty Images.

Researchers in Japan recently undertook the task of analyzing the link between diet and macular degeneration, building upon from epidemiologic studies suggesting polyunsaturated fatty acid intake can reduce early and late AMD development risk.

People greater than 40 years of age were included in the retrospective study; all had previously undergone both systemic and eye screenings. A modified version of the Age-Related Eye Disease Study classification was used to grade AMD and dietary intake was assessed using a food frequency questionnaire.

A total of 10,788 eyes—of 5,394 participants—were included. The average daily fat intake was slightly higher for women than men, at 59.0g and 52.8g, respectively. Breaking down the results by different fat types, saturated fatty acid (SFA) intake was associated with less AMD prevalence in men. There was an additional, weaker association of both mono- and polyunsaturated fatty acid intake with any AMD prevalence in men as well.

What are Fatty Acids? Saturated: The carbon chains of saturated fats have no open spots on their chain for hydrogen atoms. That is why they are called saturated. They raise LDL cholesterol (the "bad" form) and increase the risk of heart disease. Monounsaturated: These fatty acids are missing one of their hydrogen atoms due to one double bond between carbon molecules. They are healthier than saturated fats. Polyunsaturated: These fatty acids are missing more than one of their hydrogen atoms. They have significant health benefits. Omega-3 and omega-6 fatty acids belong to this group. Trans fats: This type of fat is rare in nature but has been widely used in processed foods. Trans fats are created by adding hydrogen molecules to unsaturated fats to make them shelf-stable. Trans fats are generally unhealthy, and the FDA regulates their use in food products. Source: WebMD

However, for women, there was only a marginal association found between linolenic acid intake and any AMD prevalence. Concerning severity of AMD, saturated and monounsaturated fat intake specifically showed decreased prevalence of intermediate AMD.

Importantly, the researchers highlighted in their paper on the study that these findings may be population-specific, as Asians are known to consume less foods containing saturated fatty acids than other Western populations. They additionally explained that the low intake scores found in this study for saturated fats among men may be why they saw disparate results when compared to other surveys assessing saturated fatty acid intake.

As an explanation for their differing results, the researchers proposed that “these findings suggest that SFA intake might be below the optimal level in the Japanese population and that the associations of fatty acid intakes with AMD could differ among populations with different genetic backgrounds or dietary patterns.” Following this, they warn that “optimal fatty acid intake amounts should be analyzed in the population of interest, with consideration of their source.”

Even further, the authors explained that the source of monounsaturated fat intake may be important, as another study demonstrated. The team noted that in this study, there was an association of monounsaturated fats and AMD prevalence with Portuguese participants, but not with American ones. This could be due to the mainly plant-based Mediterranean diet that Portuguese eat, higher in proportion of consuming seeds, nuts and olive oil.

AMD, which is inversely associated with higher olive oil and nut consumption, as well as a Mediterranean diet, thus may explain the discrepancy between the populations. In Japan, where the study was conducted, the sources of both monounsaturated and saturated fatty acids are similar, with the authors finding a high correlation between both intakes.

While the results of this study still need to be cross-referenced for applicability to other ethnic and geographic populations, the authors of the study believe that “these findings would help us better understand the pathogenesis of AMD and reveal interventional options to prevent or decelerate disease incidence or progression.”

Yasukawa T, Sasaki M, Motomura K, et al. Association between fatty acid intakes and age-related macular degeneration in a Japanese population: JPHC-NEXT Eye Study. Transl Vis Sci Technol. January 3, 2023. [Epub ahead of print].