What is BCAA, and why is it so popular with athletes? When looking for supplements and nutrients for athletes, you can often come across a wide selection of preparations, which bewilders and causes confusion. How do you find a supplement which perfectly meets your specific needs, is safe to use, and has the desired effects? Stocked in the plethora of shops selling supplements there are a number of categories formulated for achieving specific results. For some of these it is obligatory to mark with the mysterious abbreviation BCAA.