Yes, they can be. But it’s really a demand problem:

[W]hat, if anything, is to be done about the 150,000,000 Americans who feel they need to take supplements, either to grow muscular or to live forever? Where do their desires and superstitions come from? That dietary supplements are good for you is now as firmly ingrained in modern consciousness as that certain miracle-working icons could save you from various diseases was among elements of the Russian peasantry in the days of the Tsar and devastating epidemics. It seems that in the modern world everyone is skeptical except of what he should be.