Adding to the steaming pile of unsubstantiated hype over probiotics, the New York Times ran an uncritical article this week suggesting that a probiotic of heat-killed bacteria can treat obesity.
Of course, the data behind the story does not suggest that. In fact, the study is so small and the data so noisy and indirect, it’s impossible to come to any conclusions about efficacy. There’s also the nit-picky complaint that the study deals with dead bacteria, while probiotics are generally defined as being live bacteria. More importantly, the study was authored by researchers with a clear financial stake in the treatment succeeding. They hold a patent on the treatment and have started a company based on it—two details the New York Times seems to have forgotten to mention.
In many ways, the study is pretty typical of those on probiotics. The field is riddled with underpowered and/or poor-quality studies that use a wide mix of methods, metrics, and surrogate endpoints—that is, stand-ins for actual clinical outcomes, like measuring tumor shrinkage rather than actual cancer survival to assess a new therapy. According to a recent review of probiotics, the field’s hard-to-compare studies form a mucky mess, “collectively leading to conflicting, ambiguous, and debatable overall conclusions.”