Anthocyanosides, a class of flavonoid compounds found in deeply colored fruits such as blueberries, bilberries, and blackcurrants, have been traditionally used and scientifically investigated for their potential to support capillary health. Scientific studies have demonstrated that anthocyanosides possess strong antioxidant properties, which help protect the vascular endothelium from oxidative stress and damage. This protective effect is thought to help maintain capillary integrity and reduce capillary fragility.

Clinical trials, particularly those involving bilberry extracts (rich in anthocyanosides), have shown improvement in conditions linked to capillary fragility, such as microangiopathy and diabetic retinopathy. For example, some studies have reported a reduction in capillary permeability and improved microcirculation in patients with venous insufficiency or eye-related vascular issues after supplementation with standardized bilberry extracts. However, these studies often have limitations, such as small sample sizes and variable extract standardization, making the evidence moderate rather than robust.

Overall, anthocyanosides are used to support the capillaries based on both a tradition of use and a growing body of scientific evidence, though further large-scale, high-quality clinical trials are necessary to fully confirm their efficacy and establish optimal dosages.