Enzyme blends, often comprising proteolytic enzymes such as nattokinase, serrapeptase, bromelain, or papain, are increasingly marketed for supporting circulation and addressing poor blood flow. There is some scientific rationale behind this, primarily due to proteolytic enzymes' ability to break down fibrin, a protein involved in blood clotting. Excess fibrin can contribute to poor circulation by promoting clot formation or by thickening the blood. Nattokinase, derived from fermented soybeans, and serrapeptase, originally isolated from silkworms, have been studied for their fibrinolytic (fibrin-dissolving) activity. Small clinical trials and animal studies suggest that these enzymes may reduce blood viscosity, improve circulation, and support cardiovascular health by breaking down blood clots or preventing their formation. However, the evidence is not robust, with most studies being small, short-term, or lacking rigorous control. There is also variability in the composition of proprietary enzyme blends, which makes standardization and reproducibility of results challenging.

Despite these limitations, the use of enzyme blends for circulation finds some support in the scientific literature, though larger, well-controlled human trials are needed before firm conclusions can be drawn. The evidence base rates as moderate to low, warranting a score of 2 out of 5. Users should exercise caution, especially if taking blood-thinning medications, as enzyme supplements may increase bleeding risk.