Polyphenols are a broad class of naturally occurring compounds found in plants, including flavonoids, phenolic acids, stilbenes, and lignans. There is considerable scientific evidence supporting the use of polyphenols to support capillary health and function. Many polyphenols, particularly flavonoids (such as quercetin and rutin), have been shown to strengthen capillary walls, reduce capillary permeability, and protect vascular endothelial cells from oxidative damage. Several clinical studies and meta-analyses have demonstrated that polyphenol-rich diets or supplements can improve microcirculation and reduce symptoms of capillary fragility, such as bruising and edema, especially in populations with chronic venous insufficiency or diabetes.

The mechanisms involve antioxidant activity, inhibition of inflammation, and reinforcement of the structural integrity of capillaries. Historically, specific polyphenols like rutin were included in pharmaceutical preparations for "capillary protection." Modern research has corroborated these effects, with randomized controlled trials showing benefits from polyphenol supplementation on microvascular function, endothelial reactivity, and overall vascular health. However, the magnitude of benefit can vary depending on the type and dosage of polyphenol, as well as individual health status.

In summary, there is substantial scientific evidence supporting the use of certain polyphenols for the maintenance and protection of capillary health, validated by both mechanistic studies and clinical research.