Credit: Damian Strohmeyer / Getty Images

Ephedra or the ma huang plant is the source of ephedrine, which has been shown to be an effective treatment for asthma and low blood pressure. However, when used in high doses as an energy-boosting workout supplement like Hydroxycut, the naturally occurring compound can cause an irregular heartbeat, nerve damage, and seizures, and was linked to a number of deaths, including those of a Baltimore Orioles pitching prospect and Minnesota Vikings offensive tackle Korey Stringer. Stimulants containing ephedrine were banned in 2004, and after some courtroom battles, the compound remains illegal. Hydroxycut has since removed the substance from its products, although it once again faced the government's ire in 2009, when several of its products were recalled for causing liver damage, seizures, muscle damage, and one death.