Procyanidins are a class of polyphenolic compounds found in various plants, including grapes, apples, cocoa, and pine bark. Their use to support capillary health is primarily based on their well-documented antioxidant properties and their influence on vascular function. Several clinical studies and reviews support the notion that procyanidins, particularly those derived from grape seed extract (Vitis vinifera) and French maritime pine bark (Pinus pinaster), can improve capillary strength and reduce capillary permeability.

The mechanisms proposed include the stabilization of collagen and elastin in blood vessel walls, reduction of oxidative stress, and improvement of endothelial function. For example, randomized controlled trials have shown that procyanidin-rich extracts can decrease symptoms of chronic venous insufficiency, such as edema and capillary fragility. Additionally, in vitro and animal studies suggest that procyanidins may inhibit the degradation of capillary wall components and reduce inflammation, contributing to better capillary integrity.

Despite these promising findings, most evidence comes from studies using standardized extracts rather than unspecified procyanidins, and the quality of some trials varies. Therefore, while there is a reasonable scientific basis for the use of procyanidins to support capillary health, the evidence is moderate rather than definitive, warranting a rating of 3 out of 5.