I used to like Bill Phillip's MM2K mag for info/stuff like this. He would take products or the companies and have them analyzed to see exactly what was in them, then put the report in his mag.
I suppose a few things he brought to light was that a supplement co. can say x (on the label), is in their supp and as long as 1 or 2 caps in the bottle have that much dosage and or mgs in it, it can get a pass on the label. I don't even know what the regulations are now with supp companies.
In BSF (Bigger Stronger Faster) Chris Bell goes into supp companies and how easy it is to just start making/selling them.
I try and stick to the bigger or better known manufacturers, or wait and see some feedback or outcome by some people who have used the stuff.
I think Will Brink does some of this too, or at least used too. Have not followed his writings as much lately.
I think you have to watch when you see articles with so called great supps, peppered in the column, then on the next page, is an ad for that supplement.
I spent lots of money on supps years ago with many of them falling far short of any claims.
Just sayin'