Because The Big Mac Attack takes Androstenedione, a legal, unregulated dietary supplement that is not banned by baseball. Androstenedione is one metabolic step away from testosterone, the male sex hormone, and is classified as a dietary supplement, not a drug. While most major sports ban the substance, baseball does not. The makers of andro say that taking the pill can help produce high levels of testosterone for a few hours after taking it. The high levels of testosterone help you build more muscle faster.
Nobody really knows if it works.
Since the product is natural, and it is not proven to cause harm, the FDA doesn't even study it. What we do know is that long-term testosterone use can cause liver, kidney and heart problems, but andro makers say their product is safe because the body is making its own testosterone and not getting it from outside sources. But no long-term studies on andro have been done, so you don't know what you're getting into in the future. Although andro is not widely used, Creatine, the muscle-building, amino acid supplement used by both Mark McGwire and Sammy Sosa, remains popular among teens. Sammy Sosa is second in Major League Baseball with 64 home runs.