Are probiotics pointless—or even problematic?

Weizmann study pours cold water on the probiotics craze



Date: November 12, 2018
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Probiotic pills and yogurt

Probiotic pills and yogurt

It may be a hard pill to swallow. The widespread belief in the health benefits of probiotics—servings of live microorganisms found in yogurt and also sold in pill form—is now facing a significant challenge from laboratory science. A new Weizmann Institute study by Profs. Eran Elinav and Eran Segal shows that, in many cases, probiotics are ineffective, and, when taken after antibiotics, can even be harmful.

Some 100 trillion beneficial microbes populate the human gut—what metabolic researchers refer to as the intestinal microbiome. Commercial probiotics are sold based on the claim that such supplements have the power to repair the gut’s microbial balance after a course of antibiotics, that they can pro-actively strengthen the body’s immune response, and that they can help combat certain medical ailments. These promises are the basis of today’s multi-billion dollar probiotic industry.

But the new study raises new questions. Prof. Elinav of the Weizmann Institute’s Department of Immunology—working together with Prof. Segal of the Computer Science and Applied Mathematics Department and others—wanted to know what really happens in the human gut after taking probiotics. What they ultimately found was that individual microbiomes vary significantly, and the reaction to probiotics can differ dramatically between people.

They sampled the microbiome of healthy volunteers using endoscopies and colonoscopies, and then fed the volunteers either a commercial probiotic supplement or a placebo. When they checked for the resultant changes in the participants’ microbiome profile, the outcome was striking. First, while some study participants accepted probiotics into their gut, others just passed them from one end to the other, with no effect—therapeutic or otherwise—on microbiome composition.

These findings indicate that probiotic activity depends on the individual that takes them, and that the idea that everyone can benefit from a generic probiotic product is empirically wrong. When it comes to probiotics, the scientists concluded, one size does not fit all.

Perhaps even more stunning was the scientists’ examination of the efficacy of probiotics in restoring microbiome balance after antibiotic treatment. In the study, 21 volunteers took an identical course of antibiotics, which depleted the population of certain strains of bacteria in their gut. The participants were then assigned to three groups: the first group was given probiotics; the second, a dose of microbes derived from the participants’ own original pre-antibiotic microbiome; and the third, nothing.

In the group receiving probiotic treatment, re-establishment of participants’ normal microbiome balance was actually delayed.

“The probiotics very potently and persistently prevented the original microbiome returning to its original situation for up to six months,” says Prof. Elinav. “This was very surprising and alarming. This adverse effect had not been previously known.”

“The take-home message is that probiotics don’t always live up to their harmless reputation,” Prof. Elinav says. “To be effective, their formula needs to be tailored to the individual.”

Prof. Eran Elinav’s research is supported by the Leona M. and Harry B. Helmsley Charitable Trust; the Adelis Foundation; the Pearl Welinsky Merlo Scientific Progress Research Fund; the Rising Tide Foundation; the Else Kroener Fresenius Foundation; Vera and John Schwartz; the Lawrence and Sandra Post Family Foundation; Yael and Rami Ungar; Leesa Steinberg; Jack N. Halpern; the estate of Bernard Bishin for the WIS-Clalit Program; the Park Avenue Charitable Fund; the Hanna and Dr. Ludwik Wallach Cancer Research Fund; the European Research Council; Donald and Susan Schwarz; Valerie and Aaron Edelheit; the Howard and Nancy Marks Charitable Fund; and the estate of Malka Moskowitz. Prof. Elinav is the Incumbent of the Sir Marc and Lady Tania Feldmann Professorial Chair.

Prof. Eran Segal’s research is supported by the Crown Human Genome Center, which he heads; the Else Kroener Fresenius Foundation; the Adelis Foundation; Judith Benattar; and the European Research Council.