Bleeding risk on nattokinase (DR. HITTICH NATTOPLASMIN) plus phenprocoumon (e.g. MARCUMAR): An 86-year-old pensioner with atrial fibrillation after a treatment break took 9 mg, 6 mg and 3 mg phenprocoumon (e.g. MARCUMAR) on day 1, 2 and 3 respectively. On day 4 his INR was excessive at 6.1. At the same time he was taking nattokinase (DR. HITTICH NATTOPLASMIN) as a "dietary supplement" (NETZWERK Report 15.692). This enzyme is obtained from fermented soybeans and has a fibrinolytic effect (SUMI, H. et al.: Acta Haematol. 1990; 84: 139-43). In the literature we find another suspected report regarding a 52-year-old woman with a previous history of stroke who was taking 400 mg nattokinase daily in addition to 100 mg acetylsalicylic acid (ASPIRIN, generic) to prevent stroke recurrence. After a week, she developed severe dizziness and walking difficulties as a result of a haemorrhage in the cerebellum (CHANG, Y.-Y. et al.: Inter. Med. 2008; 47: 467-9). The Dutch company "Dr. Hittich" sells nattokinase via the internet as a "sensation for circulation and free blood flow" and a "totally safe natural remedy", which as "an enzyme with super-powers dissolves blood clots with incomparable speed" (GP Health Products B.V.: NattoPlasmin; http://www.greenpower24.com/catalog/product_info.php?products_id=11531). On their ordering pages, other suppliers indicate that consumption of nattokinase in combination with anticoagulant medication requires medical supervision and is contraindicated in the case of bleeding (e.g. Fairvital BV: Nattokinase; http://www.fairvital.com/product_info.php?products_id=587). Advertising dietary supplements with false, ambiguous or misleading health claims is banned in the European Union. Health claims must be applied for and scientifically supported (Regulation [EC] No. 1924/2006 of the European Parliament and of the Council of 20 December 2006). According to the publicly accessible register of the European Food Safety Authority (EFSA), where the evaluations can also be found, no health claim for nattokinase has so far been applied for (EFSA: Register of Questions; http://registerofquestions.efsa.europa.eu/roqFrontend). We strongly advise against taking "dietary supplements" which, like nattokinase, may have an influence on blood clotting, -Ed.