Fish oil supplements have been shown in a double-blind, randomized study to lower systolic blood viscosity and diastolic blood viscosity, both by 15%.  Five capsules were given twice daily for seven weeks (1.8 g/day), and blood viscosity tests were performed at the beginning of the study and at the end of seven weeks of supplementation [1].

Previously, dietary supplementation with omega-3 fatty acids or fish oil was shown to prevent cardiovascular events. One major study of 11,324 patients following a recent heart attack showed that fish oil supplements reduced the incidence of death, cardiovascular death, and sudden cardiac death by 20%, 30%, and 45%, respectively [2].

Separately, supplementation by the enzyme nattokinase was shown to reduce the aggregation of red blood cells and blood viscosity.  The researchers noted the potential of nattokinase for improving circulation and reducing the risk of cardiovascular disease [3].


1.  Woodcock, B., et al., Beneficial effect of fish oil on blood viscosity in peripheral vascular disease. British Medical Journal 1984; 288:592-4.

2. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto miocardico. Lancet 1999; 354:447–55.

3. Pais, E., et al. Effects of nattokinase, a pro-fibrinolytic enzyme, on red blood cell aggregation and whole blood viscosity. Clinical Hemorheology and Microcirculation 2006; 35:139-142.

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