Sweet Clover (Melilotus officinalis) has a history of use in traditional herbal medicine for circulatory disorders, particularly for supporting venous and capillary health. The plant contains coumarins, which are metabolized in the body to compounds with anticoagulant and mild vasoprotective properties. These coumarins can help improve blood flow and reduce capillary fragility, which is why Sweet Clover extracts have been studied for conditions such as chronic venous insufficiency, lymphedema, and related edema.

Several clinical studies, primarily from Europe, have evaluated standardized Sweet Clover extracts for their effects on vascular health. For example, some randomized controlled trials and observational studies have reported that Sweet Clover may reduce swelling and improve symptoms in patients with mild chronic venous disorders. The presumed mechanism is due to the plant's ability to increase lymphatic drainage and strengthen capillary walls, thereby reducing fluid leakage and tissue edema.

However, the strength of the evidence is moderate. While there is some scientific validation, most studies are small, older, or not widely replicated. Sweet Clover’s use is also constrained by safety concerns, as improper processing can lead to toxic levels of dicoumarol, a potent anticoagulant. Therefore, Sweet Clover is used in some European herbal preparations to support capillary and venous health, but its use should be approached with caution and under professional guidance.