Eating natto can cut the time it takes the body to dissolve a routine clot in half. Higher doses in tablet form are able to open up veins that are completely blocked with blood clots.
From: http://www.denvernaturopathic.com/news/natto.html
A great deal of information on natto including detailed instructions to make your own and a source for pure natto bacteria culture to make it with can be found at http://www.gaia21.net/natto/natto.htm
Tom's Blog on Life and Livingness