Natural bodybuilding is just that, natural to the human body or earth. Products like tribulus are plant extracts and therefore are natural. Products like 6-oxo are banned from natural competitions because they are just that not natural herbs or extracts. The idea of natural bodybuilding is to use what you body has (ie. making hormone levels optimal, not substituting then for chemicals) Products like creatine are considered natural because they are already in the whole foods we eat (ie beef).