Ephedra

Consider ephedra, an herbal stimulant that gained popularity as a weight-loss supplement in the 1990s — until hundreds of people reported ephedra-related problems including heart attacks, seizures and even deaths.

Athletes' use of herbal supplements has skyrocketed in the past two decades. At the top of the list of popular herbs are echinacea and ginseng, whereas garlic, St. John's wort, soybean, ephedra and others are also surging in popularity or have been historically prevalent.