Polyphenols are a diverse group of naturally occurring compounds found in plants, including fruits, vegetables, tea, coffee, and red wine. Their use in supporting or treating hypertension is primarily justified by scientific research rather than tradition. Several epidemiological and clinical studies have investigated the effects of polyphenol-rich foods and extracts—such as green tea, cocoa, and berries—on blood pressure regulation. The proposed mechanisms include improvement of endothelial function, increased nitric oxide production, antioxidant activity, and modulation of inflammation, all of which can contribute to reduced vascular resistance and lower blood pressure.

Meta-analyses and randomized controlled trials have shown that consumption of certain polyphenol-rich foods can lead to small but statistically significant reductions in both systolic and diastolic blood pressure, particularly in individuals with hypertension or pre-hypertension. For example, cocoa flavanols and green tea catechins are among the best-studied polyphenols in this context. However, the magnitude of the effect is generally modest, and the evidence is stronger for specific polyphenols or food sources rather than "unspecified" polyphenols as a broad category. There is still some heterogeneity in study results, and more large-scale, high-quality trials are needed to determine optimal types, doses, and populations who may benefit most.

In summary, there is moderate scientific evidence supporting the use of certain polyphenol-rich foods or extracts to help manage hypertension, but evidence for "unspecified" polyphenols as a category is less robust.