‘You are what you eat’: How healthy eating and living can benefit eyes, lower AMD risk
Key takeaways:
- The link between healthy diet and AMD
- Healthy lifestyle habits for patients with and at risk for AMD
The link between nutrition and ocular health became apparent in the early 1990s as epidemiologists and ophthalmologists uncovered dietary patterns in patients with AMD.
The Eye Disease Case-Control Study Group Ancillary Study, led by Johanna M. Seddon, MD, ScM, FARVO, used a specially-designed food frequency questionnaire and was the first to directly show that dietary intake of certain healthy foods, such as dark green leafy vegetables rich in lutein and zeaxanthin, were associated with a lower risk for AMD.
To learn more about more recent research, Healio spoke with Emily Y. Chew, MD, director of the Division of Epidemiology and Clinical Applications at the National Eye Institute, about how healthy lifestyle habits affect the eyes and age-related macular degeneration.
Healio: Are diet and eye health related?
Chew: You are what you eat. My parents were Chinese immigrants, and they would say things like, “These goji berries (filled with lutein) are really good for your eyes, an ancient Chinese secret.” As a kid, I never thought about it until I started doing research in age-related macular degeneration (AMD). I will discuss why this is important.
Back when researchers were looking at cardiovascular disease, cardiologists looked at the island of Crete in Greece and said, “These people don’t have any heart disease at all. What is it?” They decided it was because of their Mediterranean diet. There are lots of fruits, vegetables and legumes, low amounts of red meat and a tiny bit of alcohol, but not too much. And this diet has a higher ratio of monounsaturated fatty acids, which is seen in olive oil, and fish consumption was thought to be important.
This is interesting because a randomized trial for a Mediterranean diet in Spain has shown that there is a 30% reduction in heart disease, so clearly it is good for your heart. Similarly, we have also looked at diet and the effect it can have on the eyes.
Healio: What did your research find about the effect of diet on AMD risk?
Chew: [The Eye Disease Case-Control Study Group in the early ’90s] looked at people who had AMD and compared them with controls who were free of AMD. Using a dietary questionnaire, [the Dietary Ancillary Study] found that there were some specific [dietary] aspects that looked important for macular degeneration. Persons who ate more green leafy vegetables and fish had a lower rate of AMD.
Then, in a clinical trial, AREDS, we used vitamins and minerals — vitamin C, vitamin E, beta-carotene, zinc and copper — and evaluated the effects of the supplements on AMD and cataracts. We all thought it was going to be important for cataract, but the supplements had no effect on cataract progression. However, the supplements were beneficial for those with intermediate-stage AMD in both eyes, or in one eye with late AMD. There was a 25% reduction in the risk for developing late disease with the use of the supplements.
We also looked at diet in almost 5,000 patients who we followed for 10 years in the AREDS study. Adherence to a Mediterranean-style diet was particularly impactful in patients with dry (AMD), or geographic atrophy, especially for those eating fish twice a week. There was an almost 30% reduction in developing GA. And if you have GA, the expansion of the GA lesion was reduced in those with a high adherence to the Mediterranean diet. For people who had no or early AMD (ie those who had no evidence of large drusen) and followed a Mediterranean diet, the highest adherence to the diet resulted in a 25% reduction in the progression to large drusen, or intermediate stage.
So, progression from nothing to intermediate AMD or from intermediate to late AMD was reduced. Whether at early stage, at late stage or at moderate risk for macular degeneration, diet can have a beneficial effect, and that is pretty impactful.
Healio: What does the research say about how dietary health and supplements are associated with AMD?
Chew: It is known that use of beta-carotene has been associated with an increased risk of lung cancer in cigarette smokers. Even though we did not give beta-carotene to smokers, we found in our study AREDS2 that beta-carotene use increased the risk for lung cancer in patients who were mostly former smokers.
So, we replaced the beta-carotene with lutein and zeaxanthin, found in green leafy vegetables, like collard greens, kale and spinach. We did this trial for 5 years then followed them for another 5 years, during which we provided everyone with the oral supplements.
At year 10, we brough some of the patients back, and we had given everybody in the last 5 years the AREDS2 supplement that had lutein instead of beta-carotene. Even at 10 years, we found that there was still an increased risk for lung cancer with beta-carotene given during the first 5 years. We also found an incremental effect of lutein/zeaxanthin over beta-carotene – in other words, lutein/zeaxanthin showed a beneficial effect over beta-carotene for AMD. The AREDS2 supplements included lutein and zeaxanthin, along with vitamin C, vitamin E, zinc and copper.
Healio: How can patients with AMD benefit from regular exercise and other healthy habits?
Chew: We have not looked at exercise specifically, but we know other studies have shown that for cognition and everything else, exercise is important. We also know that patients who have increased BMI, an indication for obesity, have a higher risk for AMD. So, risk for AMD can be reduced by healthy living. Obviously, smoking is another important risk factor. That is seen in every study: The more you smoke, the more likely you are to have macular degeneration. Smoking is never good for anything, so it is important to stop that, especially for macular degeneration.
Healio: What healthy lifestyle habits would you recommend to patients with AMD?
Chew: Keeping a healthy lifestyle, keeping your weight down and not smoking are important. Adherence to a Mediterranean diet has benefits for your eyes, heart and your brain. The use of the AREDS2 supplements is also important for patients with AMD.
References:
- Age-Related Eye Disease Study Research Group. Arch Ophthalmol. 2001;doi:10.1001/archopht.119.10.1439.
- Age-Related Eye Disease Study Research Group. Arch Ophthalmol. 2001;doi:10.1001/archopht.119.10.1417.
- Agrón E, et al. Ophthalmol Retina. 2022;doi: 10.1016/j.oret.2022.03.022.
- Ajani UA, et al. Invest Ophthalmol Vis Sci. 1994. May;35(6):2725-33.
- Chew EY, et al. JAMA Ophthalmol. 2022; doi:10.1001/jamaophthalmol.2022.1640.
- Estruch R. N Engl J Med. 2013;doi:10.1056/NEJMoa1200303.
- Seddon JM, et al. Arch Ophthalmol. 2003;doi:10.1001/archopht.121.6.785.
- Seddon JM, et al.JAMA. 1994;doi:10.1001/jama.1994.03520180037032.
- The Eye Disease Case-Control Study Group. Arch Ophthalmol. 1992;doi: 10.1001/archopht.1992.01080240041025.
Editor’s note: Some additions have been made to this article for clarification purposes.
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