It's a tough project.

Nearly always the person challenging you with health nonsense will be a non-expert just like you. They won't have a deep understanding of pharmacology or physiology. They'll merely be echoing some other more primary source.

So ask the person, "Where do you get your health information?" It's a fair question. If they quote research papers, tell them that you can see they aren't scientists. Their references are copypasta from elsewhere. So where?

Many alt.med ideas can be traced back to a few web sites filled with the most apalling bullshit. If the source happens to be one of these sites, your have win. Just look around for one example of supernaturalism (e.g., homeopathy, Reiki, qi, prayer, the "innate intelligence of all living things," etc.). That's sufficient to destroy the entire web site's scientific credibility.

But wait, you say. Isn't slagging the source an ad hominem? A logical fallacy?

No. You can't dismiss an argument just because it comes from a dodgy source. But you can dismiss any factual claim from an untrustworthy party. Because acceptance of a factual claim implies acceptance of the credibility of the person making the claim.

A horselaugh is well within your rights in response to anything from a web site that tries to sell you homeopathic remedies.

Edit: I just remembered that Prince Charles dude sells homeopathic remedies. LOL!