Grape seed extract (Vitis vinifera) is widely used to support the health of capillaries and the vascular system. This use is primarily justified by scientific evidence, particularly due to the presence of oligomeric proanthocyanidins (OPCs), which are potent antioxidants found in grape seeds. Several clinical studies have investigated the effects of grape seed extract on vascular health, focusing on its ability to strengthen capillary walls, reduce capillary permeability, and improve microcirculation.

Research has shown that OPCs can protect blood vessels from oxidative stress and inflammation, both of which can compromise capillary integrity. Some randomized controlled trials have reported that grape seed extract supplementation reduces symptoms of chronic venous insufficiency, including edema and leg swelling, which are related to capillary function. A systematic review published in Phytotherapy Research (2014) concluded that grape seed extract is effective in reducing leg swelling and improving microcirculation, suggesting benefits for capillary health, although the quality and size of studies vary.

While the evidence is promising, especially in the context of venous disorders and general vascular support, more large-scale, high-quality clinical trials are needed to establish its efficacy definitively. Overall, grape seed extract has moderate scientific backing for its use in supporting capillary health.