jamieleecurtis Jamie Lee Curtis simply gushed about the performance of her colon in ads for Dannon’s probiotic-laced yogurt.It was like she couldn’t wait to go to the crapper! But now that the Federal Trade Commission has poo-pooed Curtis’s claims—it fined Dannon $21 million for false advertising—it makes you wonder what, if anything, was really going on behind the actress’s  closed bathroom doors.

jamieleecurtis In a piece published on Slate.com, writer Torie Bosch acknowledges she has lost her faith in Jamie Lee—not to mention Dannon, which was quite less than contrite about spreading untruths about the food it was selling. The company’s rationale was that lots of people believe in probiotics, science be damned.

READ THIS TALE OF DISILLUSIONMENT—A PERFECT ANTIDOTE TO HOLIDAY CHEER—ON SLATE.COM  

Dannon’s reaction to the settlement is quite telling. In a statement, the company said, “Millions of people firmly believe in, benefit from and enjoy these products, and Dannon will continue to research, educate and communicate about the benefits of probiotics on the digestive and immune systems.” It’s the “believe in” that Dannon emphasizes—and that is most troubling. If Activia doesn’t do what it claims, then does it really matter whether people “believe in” it? When it comes to health, we often cling to beliefs at the expense of evidence, as demonstrated by the appalling amounts of money spent each flu season on ineffective “supplements” like Airborne and homeopathic remedies.

Dannon’s Activia pitch depended heavily on the two-week “Activia challenge,” during which people were supposed to eat the yogurt daily and try to detect changes in digestion. But more productive trips to the bathroom during those two weeks could hardly prove that Activia was doing what it was supposed to do. Constipation can and does spontaneously stop. And, as the FTC/Dannon agreement notes, for the minor benefits of probiotics for treatment of constipation, people would have to consume three servings of Activia per day. That’s a whole lot of yogurt—and presumably most of the folks who reported positive results from the Activia Challenge weren’t eating nearly that much.

The best lesson of the Dannon debacle is that testimonials don’t equal efficacy. Personal experience doesn’t even demonstrate efficacy, since we don’t control for other factors, like fiber intake in the case of Activia or exposure to germs in the case of DanActive. Better “digestive health” while eating Activia doesn’t necessarily mean that Activia did squat. And not developing a cold while drinking DanActive doesn’t mean anything, either. Sorry, Jamie Lee Curtis, but I just don’t believe you anymore.

(Torie Bosch is a writer based in Washington, D.C. Follow her on Twitter @thekibosch)