We have always brought various supplements with us, and never had a problem. We once had an entire box of protein bars taken from our carry on and individually opened and tested for explosives though... but they eventually gave them back to us and let us on the plane.
A friend of a friend was thrown in the clink in Puerto Vallarta when she went thru customs with supplements out of their original packages. After a year, she was still in jail, trying to raise $50K for a lawyer. To be safe never travel with any medication or supplements out of their original packaging. Especially white powdery supplements like BCAA! No one wants to spend their vacay in jail.
