Polyphenols are a diverse group of naturally occurring compounds found in plants, including flavonoids, phenolic acids, and polyphenolic amides. Their use to support eye health is primarily justified by scientific evidence, though much of it is preclinical or observational rather than from large-scale randomized trials. Polyphenols, especially those found in foods like green tea, berries, and certain vegetables, exhibit strong antioxidant and anti-inflammatory properties. These properties are believed to protect retinal cells from oxidative stress, a major contributing factor in the development of age-related macular degeneration (AMD) and other degenerative eye diseases.

Several studies have shown that specific polyphenols, such as resveratrol (from grapes) and epigallocatechin gallate (EGCG, from green tea), can reduce oxidative damage in retinal cells and inhibit the formation of new, abnormal blood vessels in the eye (a process involved in wet AMD). Population studies also associate diets rich in polyphenol-containing foods with a reduced risk of cataracts and AMD. However, direct interventional studies in humans are limited, and most available research involves animal models or cell cultures.

While the mechanistic rationale is strong and some human data is promising, more robust clinical trials are needed to confirm the extent of benefit. Thus, the evidence supporting polyphenols for eye health is moderate, earning a rating of 3 out of 5.