In 2015, one of us published a peer-reviewed study, together with colleagues at the University of California, San Francisco, replicating prior research from the US Food and Drug Administration (FDA) detecting a designer stimulant, β-methylphenylethylamine, in sports, weight loss, and “cognitive function” supplements sold in the United States.1,2 The confirmatory study prompted the FDA to take enforcement action against companies selling the stimulant as a dietary ingredient.3