‘Clinically Tested’—What Does That Mean?

They used to call useless treatments “snake oil.” We don’t hear that term anymore; now they may be called “dietary supplements” or “natural remedies.” A dietary supplement may contain a single herb or a combination of several ingredients. The ads frequently say they have been “clinically tested” or “clinically proven.” Do you believe that? I don’t. From long experience, I have come to regard such claims as a red flag. 

FDA-approved drugs have been clinically proven to work; dietary supplements haven’t. If they had been clinically proven to work, they could be marketed as pharmaceuticals requiring a prescription or as FDA-approved over-the-counter medicines. The FDA doesn’t approve anything that has not been adequately tested on humans. They require evidence from controlled studies showing that the new drug is better than, or at least non-inferior to, another treatment that is known to be effective. The best studies use a placebo control, but it would be unethical to give a placebo to someone we know would be harmed by withholding an effective treatment. We couldn’t justify a control group that used an inert ingredient instead of insulin for patients with brittle diabetes, or that denied vaccines to children, or that denied antibiotics to patients with life-threatening bacterial infections. So sometimes the new pill is compared to an old pill that has been tested and is already known to work better than placebo.  

That’s probably not what the ads mean when they say a dietary supplement has been “clinically tested.” It might be true, but I’m not about to accept their word for it. I want to see the clinical studies for myself. Sometimes they make it easy for me by providing links to the studies. Sometimes it takes a lot of detective work: Googling, checking PubMed, Google Scholar, etc. I have even resorted to emailing the company and asking for the studies. This doesn’t work. If they send me links, they are inevitably to in vitro or animal studies or small, badly designed, flawed human studies—or studies of one of the ingredients in a multi-ingredient product. They are never to large, well-designed, randomized human studies testing the actual product they are selling.

Human cells can be cultured and tested in a petri dish or a test tube, but in that environment they may act very differently than they do when they are part of the human body. Animal studies can be misleading. Animal and human anatomy and physiology are similar but not identical. Proving that something is true for a mouse doesn’t mean it is true for a human; aspirin causes congenital defects when given to pregnant mice, but not when given to humans. 

The “evidence” offered for products containing multiple ingredients is often laughable. When I looked up the ingredients in a pill that was supposed to assist in weight loss, I discovered that one of the ingredients had actually been shown to promote weight gain! 

They may have searched the literature for positive studies and found a small, flawed pilot study that showed promise for a single ingredient. But what happens when you mix that ingredient with another ingredient? There are several possibilities: the effect may be additive (2 + 2 = 4), may be potentiated (0 + 2 > 2), may be antagonistic (6 + 4 < 10), or may be synergistic (2 + 2 = >>>4, maybe as much as ten times greater). There is no way to tell unless that specific mixture has been properly tested, with adequate controls. And quite often, the product in question uses a slightly different version of the ingredient or a dose that is different from the dose tested in the study they cite. 

An example: Dr. Seeds’s Chill Pills

The active ingredient in this product is dihydrohonokiol-B (DHH-B), a derivative of magnolia bark. There have been a few small pilot studies in humans testing various formulations of magnolia bark, but there have been no studies of Chill Pills. When I searched for studies of DHH-B, I found no human studies, only three studies in cultured rat hippocampal cells. I found a study of a related compound, honokiol, measuring its behavioral effects on rats in an elevated plus-maze test. It “suggested” that the rats might be experiencing less anxiety because they spent more time in the open arms of the maze. But rats can’t tell us if they feel anxious; there could well have been another explanation for that behavior. I’m reminded of another rodent study where the animals’ behavior was originally misinterpreted but was eventually explained when the researchers discovered that one of the technicians owned cats and was carrying the smell of cats into the lab. The researchers never suspected that the rats’ behavior could be affected by “eau de chat,” so they didn’t think to control for that.

Conclusion: Verification Required

As with any claim for dietary supplements (or for any claim, for that matter), it’s safest not to believe the claim unless you can find independent verification. But then you already knew you can’t believe everything you read.

I can’t help but suspect that by “clinically proven” they mean that they gave free samples to a few of their friends and relatives and then asked them a leading question such as “You feel better now, don’t you?” and recorded only the positive answers. Does that make me a cynic or only a realist? You decide. 

This article was originally published as a SkepDoc’s Corner column on the  CSI website

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

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