Various types of berries, especially those rich in flavonoids and anthocyanins (such as blueberries, blackcurrants, elderberries, and bilberries), have been studied for their effects on vascular health, including the capillaries. The scientific rationale is primarily based on the antioxidant and anti-inflammatory properties of these compounds, which are known to help protect the integrity of blood vessels. Research suggests that anthocyanins can reduce capillary fragility and permeability, which may be beneficial in conditions characterized by microvascular dysfunction or increased capillary permeability, such as diabetic retinopathy or venous insufficiency.

Clinical studies have shown that extracts from berries like bilberry can improve microcirculation and reduce symptoms such as bruising, swelling, and visual disturbances linked to fragile capillaries. However, most studies are small, use concentrated extracts, and sometimes combine multiple plant ingredients, making it difficult to isolate the effects of "berries (unspecified)." Traditional European herbal medicine also used berries, especially bilberry, for capillary support, lending some historical precedent.

While the evidence is promising and there is a plausible mechanism for capillary support, the lack of large, standardized clinical trials—especially with unspecified berries—means the evidence is moderate but not definitive.