An Australian study over 15-years suggests an independent and protective association between dietary intake of flavonoids and the likelihood of age-related macular degeneration (AMD), with cohort studies needed to validate the findings.
A study has shown that people who regularly eat oranges are less likely to develop macular degeneration than people who do not eat oranges. Researchers at the Westmead Institute for Medical Research interviewed more than 2,000 Australian adults aged over 50 and followed them over a 15-year period. The research showed that people who ate at least one serving of oranges every day had more than a 60% reduced risk of developing late macular degeneration 15 years later.
Lead researcher associate Professor Bamini Gopinath from the University of Sydney said the data showed that flavonoids in oranges appear to help prevent against the eye disease. “Essentially, we found that people who eat at least one serve of orange every day have a reduced risk of developing macular degeneration compared with people who never eat oranges,” she said. “Even eating an orange once a week seems to offer significant benefits. The data shows that flavonoids found in oranges appear to help protect against the disease.”
Gopinath said that until now most research has focused on the effects of common nutrients such as vitamins C, E and A on the eyes. “Our research is different because we focused on the relationship between flavonoids and macular degeneration.
“Flavonoids are powerful antioxidants found in almost all fruits and vegetables, and they have important anti-inflammatory benefits for the immune system.
“We examined common foods that contain flavonoids such as tea, apples, red wine and oranges. Significantly, the data did not show a relationship between other food sources protecting the eyes against the disease,” she said.
One in seven Australians over 50 have some signs of macular degeneration. Age is the strongest known risk factor and the disease is more likely to occur after the age of 50. There is currently no cure for the disease.
The research compiled data from the Blue Mountains Eye Study, a benchmark population-based study that started in 1992. It is one of the world’s largest epidemiology studies, measuring diet and lifestyle factors against health outcomes and a range of chronic diseases.
“Our research aims to understand why eye diseases occur, as well as the genetic and environmental conditions that may threaten vision,” Gopinath concluded.
Background: The majority of research performed to date has examined the effects of commonly known antioxidants such as vitamins C, E, and A and carotenoids on age-related macular degeneration (AMD) risk and progression. To date, there is limited research on promising phytochemicals with antioxidant and anti-inflammatory properties, including flavonoids.
Objective: In this exploratory study, we aimed to assess the independent associations between dietary intake of total flavonoids and common flavonoid classes with the prevalence and 15-y incidence of AMD.
Design: In this population-based cohort study, 2856 adults aged ≥49 y at baseline and 2037 followed up 15 y later were included in prevalence and incidence analyses, respectively. Dietary intake was assessed by using a semiquantitative food-frequency questionnaire (FFQ). Estimates of the flavonoid content of foods in the FFQ were assessed by using the USDA Flavonoid, Isoflavone, and Proanthocyanidin databases. AMD was assessed from retinal photographs.
Results: In cross-sectional analysis, each 1-SD increase in total overall flavonoid intake was associated with a reduced likelihood of any AMD (multivariable-adjusted OR: 0.76; 95% CI: 0.58, 0.99). Each 1-SD increase in dietary intake of total flavonols and total flavanones was associated with reduced odds of the prevalence of any AMD [multivariable-adjusted OR (95% CI): 0.75 (0.58, 0.97) and 0.77 (0.60, 0.99), respectively]. A marginally significant trend (P = 0.05) was observed between increasing the intake of total flavanone and hesperidin (from the first to the fourth quartile) and reduced likelihood of incident late AMD, after multivariable adjustment. Participants who reported ≥1 serving of oranges/d compared with those who never consumed oranges at baseline had a reduced risk of late AMD 15 y later (multivariable-adjusted OR: 0.39; 95% CI: 0.18, 0.85).
Conclusions: Our findings suggest an independent and protective association between dietary intake of flavonoids and the likelihood of having AMD. Additional prospective cohort studies are needed to validate these findings.
Bamini Gopinath Gerald Liew Annette Kifley Victoria M Flood Nichole Joachim Joshua R Lewis Jonathan M Hodgson Paul Mitchell