Often overlooked about testosterone-boosting supplements is whether, even if they caused a minor rise in testosterone, it would be enough to generate any gains in mass. The few such products that have been studied yield little or no changes in body composition, including muscle. Some studies have reported a 42 percent rise in testosterone in human subjects due to a highly touted amino, D-aspartic acid. That pales in comparison to the results people get from using actual anabolic steroid drugs. So there is no evidence whatsoever that using a supplement such as D-aspartic acid will lead to muscle gains. Nor is there any long-term toxicity study on the substance that proves its safety.