I started taking Nattokinase (2000 fu, once a day) a few months ago instead of a daily aspirin for heart attack and stroke prevention after reading studies on it. Interestingly, I got a slight case of tinnitus for a few minutes within 2 hours only the first two days of taking it.. just in my left ear. Felt like the inner ear was adjusting to increased blood flow. The noise went high pitched and then quiet. I also got a temporary pain in my left temple/brain. I suspect thought I don't know for sure this was a sign of carotid artery circulation improvement. Well I ran out of my nattokinase a couple of weeks ago. I ordered it online and had a week off of it while I waited for it to arrive. I started back on a few days ago and got the exactly same symptoms. Just for a day as my body adjusted to the supplement again. I am wondering if anyone else on this site had the same symptoms on Natto?