https://astralcodexten.substack.com/p/how-trustworthy-are-supplements

[EDIT: LabDoor responds here]

[Epistemic status: not totally sure of any of this, I welcome comments by people who know more.]

Not as in "do supplements work?". As in "if you buy a bottle of ginseng from your local store, will it really contain parts of the ginseng plant? Or will it just be sugar and sawdust and maybe meth?"

There are lots of stories going around that 30% or 80% or some other very high percent of supplements are totally fake, with zero of the active ingredient. I think these are misinformation. In the first part of this post, I want to review how this story started and why I no longer believe it. In the second and third, I'll go over results from lab tests and testimonials from industry insiders. In the fourth, I'll try to provide rules of thumb for how likely supplements are to be real.

I. Two Big Studies That Started The Panic Around Fake Supplements

These are Newmaster (2013) and an unpublished study sponsored by NY attorney general Eric Schneiderman in 2015.

Both used a similar technique called DNA barcoding, where scientists check samples (in this case, herbal supplements) for fragments of DNA (in this case, from the herbs the supplements supposedly came from). Both found abysmal results. Newmaster found that a third of herbal supplements tested lacked any trace of the relevant herb, instead seeming to be some other common plant like rice. Schneiderman's study was even more damning, finding that eighty percent of herbal supplements lacked the active ingredient. These results were extensively and mostly uncritically signal-boosted by mainstream media, for example the New York Times (1, 2) and NPR (1, 2), mostly from the perspective that supplements were a giant scam and needed to be regulated by the FDA.

The pro-supplement American Botanical Council struck back, publishing a long report arguing that DNA barcoding was inappropriate here. Many herbal supplements are plant extracts, meaning that the plant has one or two medically useful chemicals, and supplement manufacturers purify those chemicals without including a bunch of random leaves and stems and things. Sometimes these purified extracts don't include plant DNA; other times the purification process involves heating and chemical reactions that degrade the DNA beyond the point of detectability. Meanwhile, since supplements may include only a few mg of the active ingredient, it's a common practice to spread it through the capsule with a "filler", with powdered rice being among the most common. So when DNA barcoders find that eg a ginseng supplement has no ginseng DNA, but lots of rice DNA, this doesn't mean anything sinister is going on.