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In the news: Plant-Based Diet for Eye Health? Clinical Trials to Watch

Pescatarian Diet May Lower AMD, Cataract Risk

An increased risk of age-related eye diseases has been observed in those eating unbalanced diets, while a plant-based diet has been linked to lower risk. But is there a simple answer for patients who ask what kind of diet might best help them retain ocular health as they age?

Results of a systematic review and meta-analysis(1) by Canadian university researchers sheds some light on how that question might be approached. The investigators sought to characterize the relationship between plant-based diets and age-related ocular outcomes among adults. To do so, they chose studies that focused on observed visual changes due to a reduced intake of animal products.

Twenty-one studies met the screening criteria: 15 studies (n= 51,695) assessed the impact of fish consumption, 8 studies (n=28,753) analyzed the effect of red meat intake, and 3 studies (n=7,723) assessed omitting skim milk, poultry, and non-meat animal products, on age-related macular degeneration (AMD) or cataract development.

Meta-analysis indicated that regular fish intake reduced the risk of the risk of age-related eye disease development by 30% (OR 0.70), as did the consumption of skim milk, poultry, and non-meat animal products (OR 0.70). In contrast, consumption of red meat increased that risk by 41% (OR 1.41).

The authors conclude that a pescatarian diet is associated with the most favorable visual outcomes, while consuming red meat negatively affects ocular health. The Mediterranean diet is very similar to a pescatarian diet, in that it emphasizes eating seafood, fish, eggs and dairy, vegetables, fruits, whole grains, healthy fats and nuts. It differs in that it allows for minimal red meat and poultry intake. A reasonable patient recommendation might be to follow the Mediterranean diet (also found to lower the risk of AMD), but to eat red meat infrequently.

New Trials Examine Issues of Interest

Vitamin D Deficient / marginal vitamin D blood levels have been linked to the risk of chronic health conditions, although the VITAL trial (the largest randomized clinical trial in the world) did not show reductions in major health outcomes except for autoimmune disease and advanced cancer.

Vitamin D has anti-inflammatory effects as evidenced by the reduction in autoimmune diseases seen in VITAL and recent insights from Purdue University and the NIH into how vitamin D functions to reduce inflammation caused by immune cells. Thus, the question has been raised whether vitamin D could be beneficial in reducing the severity of COVID illness, the need for hospitalization, and long COVID.

A new intervention trial(2) (Vitamin D for COVID or VIVID trial), led by Dr. JoAnn Manson of Harvard is designed to address those questions. Now underway, the study is testing a dose of > 3,000 IU vitamin D/day in over 2,000 participants. The results should be available by the end of this year or early next year.

Genetic Testing and Lifestyle Behaviors for AMD Risk Although the American Academy of Ophthalmology currently does not recommend routine genetic testing for complex diseases such as AMD, some prevention-minded researchers have asked whether testing might have a role in helping prevent the disease. Would informing people of their genetic risk be incentive to improve their behaviors related to eye health?

Led by Dr. Paul Bernstein of the University of Utah, a new study(3) (The Moran AMD Genetic Testing Assess-ment Study or MAGENTA) will assess the impact of genetic testing for AMD on lifestyle behaviors as measured by systemic and ocular carotenoid status. Of the anticipated 80 healthy participants, one group will have genetic testing results disclosed immediately, while the other group won’t receive results until the end of the one year study. The study is estimated to be completed by the end of August, 2024.

References

1. Cirone C, et al. Linkage between a plant-based diet and age-related eye diseases: a systematic review and meta-analysis. Nutr Rev. nuac067, Sept. 14, 2022.
2. Clinicaltrials.gov, Identifier NCT04536298
3. Clinicaltrials.gov, Identifier NCT05265624