Near-death experience with nattokinase

This is a true story that I personally witnessed.

A 60-some year old man heard that nattokinase "thinned the blood." So he had been taking it for the past 6 months.

One week before he came to see me, he abruptly became quite breathless. He was unable to walk more than 20 feet or bend over to tie his shoes due to the breathlessness.

He came to see me in the office. I was alarmed by how breathless he was without signs of heart failure or other obvious explanation. I sent him for an immediate CT pulmonary angiogram. Within 30 minutes, we had the diagnosis: a large "saddle" pulmonary embolus, meaning a large blood clot that straddled the right and left main pulmonary arteries. One wrong move and . . . bang! He would have been dead within a couple of minutes, since a large clot can completely occlude the large arteries feeding the lung, essentially corking any blood circuiting through the lungs and back to the left side of the heart. (Causing, incidentally, electromechanical dissociation, in which the heart keeps beating for a few minutes but no blood is being pumped. CPR can keep you alive for a few minutes, then it's over.)

When I advised the patient of the diagnosis (after initiating the REAL anticoagulants), he said, "But I was taking nattokinase!"

Exactly. Blood clots are no laughing matter. They are potentially fatal events. Betting your life on some company's advertisement is nothing short of foolish.

Anyone who reads The Heart Scan Blog knows that I am an avid supporter of nutritional supplements. I even write articles and consult for the supplement industry. But I truly despise hearing unfounded marketing claims that some supplement companies will make in the pursuit of a fast buck.

There is no doubt that we need better, safer methods to deal with dangerous blood clots, whether in the lung, pelvis, or other areas. But, before anyone takes a leap based on the extravagant marketing claims made by a supplement manufacturer, you want to be damn sure there are real data--not marketing claims, REAL data--before you use something like nattokinase in place of a proven therapy.

Don't confuse the very interesting, though unpalatable, natto with nattokinase. Natto contains vitamin K2 and some other interesting compounds, including nattokinase.

Comments (22) -

  • Anonymous

    5/15/2010 10:41:58 PM |

    Interesting that your warning about nattokinese is FOLLOWED immediately by an advertisement for.... nattokinase extracts!

  • mongander

    5/16/2010 1:29:07 AM |

    Actually most nattokinase does not contain vitamin K2.  When nattokinase is extracted from natto, the K2 is separated and sold as another profitable byproduct.

  • Anonymous

    5/16/2010 1:29:07 AM |

    Wait a minute though! Was there any indication that he needed a real blood thinner before his clot? Maybe he was just taking it like a daily aspirin to "thin the blood" not for therapeutic blood anticoagulation. His clot was unfortunate but probably could have occurred with a cardiologist sactioned baby aspirin.

  • Dr. William Davis

    5/16/2010 1:07:24 PM |


    He was taking aspirin, as well.

    However, aspirin does NOT prevent deep vein thromboses that lead to pulmonary emboli, regardless of dose. Aspirin is a platelet-inhibitor, not a true "blood thinner" that works by way of clotting proteins.

  • sfr

    5/16/2010 2:18:50 PM |

    Was he using nattokinase as an excuse not to take his warfarin, or something like that? Otherwise it seems very unlikely that the nattokinase had anything to do with the clot. If anything, I'd worry about nattokinase causing bleeds, not clots.

  • Anonymous

    5/16/2010 5:58:24 PM |

    Curious if you ever recommend pycnogenol in cases where there is a risk of DVT? I believe there is at least one study showing a reduced risk of DVT in those who took pycnogenol.

    I'm not saying it's better than anti-coagulants, but it may be better than aspirin.

  • Myron

    5/16/2010 6:08:01 PM |

    Real anti-coagulants?  Like the red clover extract coumadin?  Patients on coumadin even with careful control often suffer excessive bleeding or more clots and strokes.    
    I guess the point is that clotting control is very difficult and that the number one drug is a natural medicine, herbal extract.

  • Anonymous

    5/16/2010 11:25:24 PM |

    One time, I was at a local vitamin shop when I saw that the supplement I was thinking about buying contained nattokinase.  Having read your blog and knowing what you think of nattokinase, I put the product back on the shelf.  The proprietor of the shop asked me why I did not want that supplement, because in his opinon it was a very good product.  I said that I did not want to take anything with nattokinase in it, and he said, "What do you have against nattokinase?"  I didn't bother to explain myself to him, figuring that I would just be wasting my breath.

  • Eric

    5/17/2010 1:37:14 AM |

    What is your opinion about doing higher dose mixed tocopherols, which do work on the clotting cascade. Or garlic and omegas which decrease platelet aggregation. What is your stand on normalizing your vitamin K content and then titrating your dosage of coumadin up to theraputic INR. As far as the nattokinase is concerned, do you like any of that style of enzyme? lumbokinase, serrapeptase. Although they don't have any effect on INR they should have an affect on FDPs

  • Paul

    5/17/2010 3:40:36 AM |

    That title is misleading.  People have been known to have near death cardiac events while taking fish oil, vitamin D3, and high dose niacin too.

    As well, on rare occasion, people have been known to have a recurrent DVT and/or PE while on warfarin therapy, even with an INR as high as 2.5.  Therefore, does that mean warfarin is an ineffective anticoagulant?  Of course not.

    This whole blog is about how we as individuals need to take control of our own health.  That just because we're taking a therapeutic medication or supplement, it does not therefore absolve ourselves from further investing in a life style that is proven to lower risk factors that may cause catastrophic health events.  

    I totally agree that some of the marketing claims made concerning nattokinase are inflated and frankly, unbelievable - particularly about its capabilities as a thrombolysis.  And I agree that if your doctor advices that you need heprin or warfarin therapy in order to prevent a catastrophic health event, you certainly need to heed that advice.

    But, count me down as someone who has extensively studied this subject and is still open to the possibility that nattokinase may contain some attributes in the prevention of venus thrombosis from a novel approach that needs further clinical investigation.

  • Dave

    5/17/2010 3:57:54 PM |

    Dr. Davis,

    I wouldn't be so quick to blast nattokinase because of this isolated incident or lack of research.

    Nattokinase is a "mild" blood thinner. Taking it once a day will not do more than relieve inflammation and slightly improve a person's circulation.

    A person would have to take it every 4 times a day (800 IU) on an empty stomach for if he desires a therapeutic effect. I would be curious if this patient of yours even took 200 IU per day (because a lot of products don't even contain that much).

    I have personally witnessed an improvement in circulation after taking nattokinase.

  • Dave

    5/17/2010 4:03:09 PM |

    I would like to add one more thing...

    I'm sure you have had experience with patients who took 400 IU of vitamin D in tablet form, and did not see any results after six months either. Was it because vitamin D is a worthless supplement, and should not be used?

  • Dave

    5/17/2010 4:42:33 PM |

    Sorry, I was misspoke about the dosage. Nattokinase is measured in fibrinolysis units (FU), not IU, and the effective dose ranges anywhere from 2,000-8000 FU per day.

    Also, here's actual scientific research (albeit small), not marketing hype, on nattokinase.

  • StephenB

    5/17/2010 6:40:37 PM |

    I've like the taste of natto from the moment I tried it. I am, however, a bit weird. ;)

  • Aaron

    5/17/2010 8:19:54 PM |

    Dr. Davis -- my question here is, could the nattokinase cause the blood clot (doesn't seem the be the case)?  Are you saying that it didn't matter that he was taking nattokinese because it doesn't reach the bloodstream to clear clots (so he would of had the clot anyway)

    Secondly, if he was taking nattokinese that had vitamin K2 <--- is it possible that increases in K2 might cause abnormal blood cloting?

  • Dr. William Davis

    5/17/2010 9:44:34 PM |

    Vitamin K2 does not cause blood clotting any more than topping up your gas tank makes your car go faster.

    Whether nattokinase has other effects is not my point. My concern is that people frequently ask if they should treat their DVT or pulmonary embolus with nattokinase. This is a death sentence. It should NOT be used for a such a purpose unless there were a large treatment trial proving equivalence or superiority to existing therapies.

  • Paul

    5/18/2010 12:50:58 AM |


    High dose mixed tocopherols use the same mechanisms as Wafarin/Coumadin.  They block the reabsorption of vitamin-K in the liver.  Vitamin-K is necessary for the liver to synthesize and release clotting proteins in the blood.  Warfarin/Coumadin is much, much more consistent than tocopherols in maintaining vitamin-K malabsorption and a safely prescribed INR range.  

    Titrating a Warfarin/Coumadin dosage never made sense to me. It is not toxic other than causing vitamin-K deficiency. What difference does it make if the dosage is 20 mg or 20 mcg to maintain a therapeutic INR?  Your liver will need to be equally deficient in vitamin-K no matter how you caused the deficiency.

    Garlic, ginger, ginkgo, curcumin, n-3, aspirin, N-acetylcysteine, Plavix, and yes tocopherols too all are anti-platelet agents.   They are effective at preventing arterial thrombosis, where anticoagulants have little effect. Conversely, anticoagulants are effective at preventing venous thrombosis, where anti-platelet agents (unfortunately) have little effect.

  • Michaela

    5/18/2010 7:36:40 AM |

    I'm giving my son nattokinase, one tablet daily and he also takes Vitamin K2. He has not been prescribed blood thinners, only aspirin which I stopped many months ago.
    Are you warning of not replacing prescribed blood thinners with natural therapies?
    If blood thinners have not been prescribed, is it of benefit to supplement with nattokinase?

  • rob_scheuneman

    5/18/2010 11:31:00 PM |

    Hi Dr. Davis

    I was wondering if you could help me with something.

    I've been monitoring my blood glucose recently with a basic monitor, and my readings would suggest that I am on the verge of impaired glucose tolerance, but not quite there yet.

    I was reading about continuous glucose monitoring systems. I would love to have on if these to more thoroughly monitor my blood glucose, but every model out there requires a prescription to obtain one. I don't understand this, because they are not dangerous in any way.

    Do you know of any way a non diabetic can purchase one of these?

    Any information you can give me would be greatly appreciated. Thank you.


  • Anonymous

    9/25/2010 9:36:39 PM |

    Dr. Davis, i am a 45 year old female who recently started taking Lovasa for high triglycerides , i am also on garlic tabs and one baby asprin per day . Is is safe to replace the garlic and asprin with one tab of Natto- K per day and is it safe to take with Lovasa? I am about 20 lbs overweight do not drink or smoke and swim and or walk 3 days per week. i am genetically predisposed to high triglycerides but never had a problem until i gained the weight. Until i get the weight off i am trying a more natural approach. Help!

  • Kelly D

    8/10/2013 3:24:08 AM |

    Acta Haematol. 2010;124(4):218-24. doi: 10.1159/000321518. Epub 2010 Nov 13.

    In vivo evaluation method of the effect of nattokinase on carrageenan-induced tail thrombosis in a rat model.
    Kamiya S, Hagimori M, Ogasawara M, Arakawa M.
    Nagasaki International University, Sasebo, Japan.

    Thrombosis is characterized by congenital and acquired procatarxis. Nattokinase inhibits thrombus formation in vitro. However, in vivo evaluation of the therapeutic efficacy of nattokinase against thrombosis remains to be conducted. Subcutaneous nattokinase injections of 1 or 2 mg/ml were administered to the tails of rats. Subsequently, κ-carrageenan was intravenously administered to the tails at 12 h after nattokinase injections. The mean length of the infarcted regions in the tails of rats was significantly shorter in rats administered 2 mg/ml of nattokinase than those in control rats. Nattokinase exhibited significant prophylactic antithrombotic effects. Previously, the in vitro efficacy of nattokinase against thrombosis had been reported; now our study has revealed the in vivo efficacy of nattokinase against thrombosis.

    PMID: 21071931