Has it occurred to you that the health supplement buyer is in a much better position to decide how to allocate their money than you are? You have limited, aggregate information; they have a total view of their own finances and life situation, and are willing to devote their own time to research their personal decision to buy. For example, they might discover through research that a supplement generally regarded as a placebo has a benefit under circumstances known only to the them.
When you limit the choices of others, based only on general information or your personal perspective, you limit the set of choices others may take. If you do this long enough, you might find yourself some day prohibited from buying something you desperately need, because your situation is an exception to some general rule that nobody ever considered.
The FDA might have made sense at a time when most people were illiterate and information was hard to come by. Now that most (at least in the US) are literate, and own smartphones, taking away choices for the benefit of some hypothetical illiterate serves only to worsen the life of the average person.