I had also tried the zma from quamtrax, which was also very good, and I decided to take this one from nutrend because the previous one had run out. Besides helping me sleep even better and for more hours, I have noticed a difference in testosterone levels. Because I generally wake up intermittently during the night without fully waking up and fall asleep again, I notice every time I wake up an erection (this didn't happen to me even when I was 15) and also when I wake up in the morning daily, which didn't happen with the previous zma. This may also be due to the effects of changing my diet (lots of whole eggs, meat, and plenty of seafood), but I believe that the zma has done its job as well. I will definitely be taking this zma from now on!