Dietary Flavonoid Intake and Chronic Sensory Conditions: A Scoping Review

Flavonoids, naturally occurring polyphenolic compounds found in a wide variety of plant-based foods and beverages, offer numerous health benefits due to their antioxidant, anti-inflammatory, and vascular properties. This scoping review investigates the association between dietary flavonoid intake and chronic sensory conditions, specifically age-related eye conditions and hearing problems in adults. Eye Health Benefits Flavonoids have shown promising results in protecting against various age-related eye conditions. Key findings from the review indicate:

• Age-Related Macular Degeneration (AMD): Higher intake of dietary flavonoids, especially flavonols, is associated with a reduced risk of AMD.
• One study found that consuming at least one serving of oranges daily significantly reduced the risk of developing late-stage AMD over 15 years.
• Flavonols may enhance nitric oxide production and improve endothelial function, reducing oxidative stress in retinal pigment epithelium cells.

• Cataract: A population-based cohort study highlighted that lower intake of flavonols (quercetin and isorhamnetin) significantly increased the risk of developing cataracts.
• Flavonols may protect against cataract formation by promoting antioxidant enzymes and inhibiting aldose reductase, an enzyme involved in diabetic complications.

• Glaucoma: Dietary flavonoid intake, particularly flavonols, may reduce the risk of primary open-angle glaucoma by 18%.
• The antioxidative properties of flavonoids help mitigate oxidative damage in the trabecular meshwork, maintaining intraocular pressure within normal levels.
• Consumption of flavonoid-rich tea, such as green or black tea, was linked to a lower risk of glaucoma.

• Diabetic Retinopathy: Higher consumption of flavonoid-rich fruits and vegetables correlates with lower levels of C-reactive protein, HbA1C, and glucose, reducing the odds of diabetic retinopathy by 33%.

Hearing Health Benefits The review also explored the impact of dietary flavonoids on hearing health, though findings are less conclusive compared to eye health:

• Hearing Loss: One study suggested a 36% lower risk of incident hearing loss with higher intake of isoflavones, primarily from soy-based products.
• The role of flavonoids in enhancing endothelial function could potentially protect against cochlear damage caused by oxidative stress and inflammation.

• Tinnitus: There is insufficient evidence to establish a protective association between dietary flavonoid intake and the prevention of tinnitus.
• Further research is needed to explore the potential benefits of flavonoids in managing tinnitus.

Research Gaps and Recommendations While the review provides encouraging evidence supporting the protective role of flavonoids in eye health, it also identifies significant gaps in research. Most sensory conditions, including hearing loss and tinnitus, lack sufficient studies to draw definitive conclusions. The review recommends conducting more high-quality, randomized controlled trials to confirm the associations and understand the underlying mechanisms of flavonoids in sensory health. Conclusion Dietary flavonoids, particularly flavonols, show promise in protecting against age-related eye conditions such as AMD, cataracts, and glaucoma. However, the evidence for their benefits in hearing health remains limited. Further research is essential to substantiate these findings and potentially guide dietary recommendations for preventing and managing chronic sensory conditions.