This was all made legal in the Dietary Supplement and Health Education Act of 1994.
Before that, everythimg required FDA approval, but now if it says “natural” or “not intended to treat any condition” on the side, you can bottle and sell your own piss if you’ve got a good enough sales pitch
The Biden Admin just announced an executive order removing de minimis tax protections from large companies trying to exploit it to import large quantities of product, which is going to take a bite out of Shein and Temu’s business models.