Proanthocyanidins, a class of polyphenolic compounds found in foods like grapes, pine bark, and cocoa, have been studied for their potential benefits in supporting vascular health, including the treatment of varicose veins. The scientific rationale is based on their antioxidant properties, ability to strengthen capillary walls, and improve venous tone. Several clinical studies, especially those using standardized extracts such as French maritime pine bark (Pycnogenol) and grape seed extract, have investigated their effects on chronic venous insufficiency (CVI), which underlies varicose veins.

Randomized controlled trials and meta-analyses suggest that proanthocyanidins can reduce symptoms such as leg swelling, heaviness, and discomfort in people with CVI. A 2016 meta-analysis in the International Angiology journal found that pycnogenol and grape seed extract, both rich in proanthocyanidins, significantly improved microcirculatory parameters and reduced edema compared to placebo. These effects are attributed to improved capillary resistance, decreased vascular permeability, and reduction of inflammation.

However, most studies use specific, standardized extracts and not generic or unspecified proanthocyanidins, and the quality and scale of studies vary. While evidence supports a beneficial role, especially as an adjunct to conventional therapy, more large-scale, high-quality trials are needed to determine efficacy and optimal dosing. Thus, the evidence can be considered moderate (3/5) and primarily scientific, though some traditional use exists in herbal medicine.