Harvard Heart Letter

Ask the doctor: Can I take nattokinase instead of warfarin?

Ask the doctor

Can I take nattokinase instead of warfarin?

Q. I would like to find a safer, easier alternative to warfarin, which I have been taking for a couple of years. I have been hearing about nattokinase "" can I take it in place of warfarin?

A. Nattokinase, an enzyme extracted from fermented soybeans, helps dissolve blood clots "" in test tubes. But there's barely a scrap of evidence showing that taking nattokinase or eating natto (the fermented beans themselves) breaks up blood clots in human arteries or prevents them from forming in the first place.

So far there are just two studies. A study of 12 adults in Japan showed that nattokinase capsules taken three times a day gradually increased the body's natural clot-busting ability in some of the volunteers; unfortunately, the results weren't reported for all of them. The second study tested a combination of nattokinase and pycnogenol (an extract of French maritime pine) in 101 people taking long air flights. The combination reduced deep-vein blood clots and leg swelling better than placebo tablets. But there is no way to tell if the nattokinase, the pycnogenol, or something else did the trick.

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