i dont know why you guys just listen one thing from someone and share with everyone everywhere, without knowing nothing or researching personally about supplements,
yes it can be harmful for you only in the way if you dont know what u r using and dont know what you are doing , its just like you eat 10 eggs a days and dont do anything worthy to them ! you will be sick ofc
supplements are good, its supplements of your diet , if you get them original + in balanced ratio + enough workouts then everything will be perfect
so only the thing you should be worried about that supps are fake or local made , only those might be harmful