Before you buy any supplement, you have to check the label for “other ingredients - this is where you will see all the bulking agents and ‘unhealthy’ ingredients of the supplement.
So the supplement companies will normally tell you all the ‘good’ ingredients at the top. But whats more important is further down the label - normally in smaller writing where it says “other ingredients"; and that’s normally where they tell you all the ingredients that they don't want to shout about
When shopping for supplements, always look at the other ingredients because it tells you a lot more about the supplement than just all the beneficial stuff.