Japanese sophora (Sophora japonica), particularly its dried flower buds known as "Huai Hua Mi" in traditional Chinese medicine, has a long history of use for supporting vascular health, including capillary integrity. The main active constituent, rutin (a flavonoid glycoside), has been extensively studied for its vascular protective properties. Rutin is known to strengthen capillary walls, reduce capillary permeability, and exhibit antioxidant effects, which are important for maintaining capillary health and function.

Scientific studies have demonstrated that rutin and related flavonoids can reduce capillary fragility and permeability, potentially preventing microvascular bleeding and edema. Some clinical trials and animal studies have shown that rutin supplementation decreases symptoms associated with chronic venous insufficiency and can reduce bleeding tendencies in conditions such as hemorrhoids or varicose veins. Additionally, rutin is recognized in some pharmacopeias for its role in treating capillary disorders.

While much of the research is based on isolated constituents such as rutin, and not always on the whole plant or flower bud, the scientific evidence supporting the use of Japanese sophora for capillary support is moderate. More high-quality, large-scale human trials are needed for conclusive evidence, but the existing data from both traditional use and modern research provide a reasonable basis for its inclusion in products targeting the capillary system.