ZMA may have helped testosterone levels because the mineral zinc and magnesium play important roles in the production of anabolic hormones, especially testosterone. The study participants were shown to have borderline deficient levels of both minerals at the beginning of the study, so raising their levels to normal could have accounted for the rise in testosterone.
I wouldn’t rule out ZMA completely, most people in the U.S. are deficient in both zinc and magnesium. If you are slghtly deficient in zinc and/or magnesium ZMA could increase your testosterone production by bringing your levels back to normal. 8 out of 10 stars!
Tribulus Terrestris – This is a weed that grows in temperature and tropical climates and has been used for centuries to increase libido in males. Does it also increase testosterone levels as many supplement companies would have you believe? That depends on who is taking it.