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

Content provided by the Faculty of the Harvard Medical School

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.

These very slim and very preliminary findings have been spun into a tale of nattokinase wonder cures. Don't be taken in by these empty promises. It's perfectly okay to eat natto — strong-stomached folks have been consuming this pungent food for generations. Whether you'll get anything out of it besides tingling taste buds is an open question. Nattokinase, a purified enzyme extracted from natto, is a different kettle of fish. It is more an untested drug than a "dietary supplement."

If clinical trials ever show that nattokinase safely replaces warfarin, we'll put it on page one. Until then, stick with warfarin. It may be inconvenient, but it's also a proven lifesaver.

— Thomas Lee, M.D. Editor in Chief, Harvard Heart Letter

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Last updated:	September 05, 2008

Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.

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