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Zinc: Another potent ingredient to add to any testosterone booster is zinc. This study shows how zinc is able to prevent a decline in testosterone levels during intense and hard workouts performed by wrestlers. Researchers found that the group who was administered with a placebo had a reduction in testosterone, as opposed to the group who were supplemented with zinc. The placebo group had a notable drop in their testosterone count during this process. Zinc has also been shown to increase the number of free testosterone and lower SHBG.