Blueberry (unspecified species, but typically referring to Vaccinium spp.) is often used to support capillary health, primarily due to its high content of anthocyanins and other flavonoids. These compounds have been studied for their antioxidant and vasoprotective properties. Several in vitro and animal studies suggest that anthocyanins can help stabilize capillary walls, reduce permeability, and decrease oxidative damage to vascular tissues. Human studies are more limited, but some clinical trials and observational studies have reported improvements in endothelial function and markers of vascular health after blueberry or anthocyanin consumption. For example, a 2019 randomized controlled trial published in the American Journal of Clinical Nutrition found that daily blueberry intake improved endothelial function in healthy adults.

However, while the evidence is promising, it is not as robust or specific as that for bilberry (Vaccinium myrtillus), a close relative of blueberry, which has more direct traditional and scientific support for capillary and microvascular protection. The majority of evidence for blueberries relates to general cardiovascular and metabolic health, rather than specifically to capillary function. Thus, the use of blueberry for capillary support is justified by scientific evidence, but the strength of this evidence is moderate (rated 3 out of 5) due to the need for more targeted clinical research.