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If you're familiar with the history of Activia, you may not be surprised.
Any striking marketing claims in companies' ads about the gut benefits of a popular probiotic may be full of, well, the same thing that has their target audience backed up.
In a randomized controlled trial, the probiotic Bifidobacterium animalis subsp. lactis—used in many probiotic products, including Dannon's Activia yogurts—did nothing to improve bowel health in people with constipation, according to data from a randomized triple-blind placebo-controlled clinical trial published Wednesday in JAMA Network Open.
The study adds to a mixed and mostly unconvincing body of scientific literature on the bowel benefits of the bacterium, substrains of which are sometimes sold with faux scientific-sounding names in products. Dannon, for instance, previously marketed its substrain, DN-173 010, as "Bifidus regularis."
Digested data
For the new study, researchers in China recruited 228 middle-aged adults, 85 percent of whom were women. The participants, all from Shanghai, were considered healthy based on medical testing and records, except for reporting functional constipation. This is a condition defined by having two or more signs of difficulty evacuating the bowels, such as frequent straining and having rock-like stool. For the study, the researchers included the additional criterion that participants have three or fewer complete, spontaneous bowel movements (CSBMs) per week.
The participants were randomized to take either a placebo (117 participants) or the probiotic (112 participants) every day for eight weeks. Both groups got packets of sweetened powder that participants added to a glass of water taken before breakfast each morning. In addition to a sweetener, the daily probiotic packets contained freeze-dried Bifidobacterium animalis subsp. lactis substrain HN019, which is used in some commercial probiotic products. The first dose had a concentration of 7 × 109 colony-forming units (CFUs), then participants shifted to a daily dose of 4.69 × 109 CFUs. Many probiotic products have doses of B. lactis in ranges from 1 × 109 to 17 × 109.
Throughout the eight-week study, participants kept a daily diary, recording any changes in CSBM frequency, which was the primary focus of the study. But the diary entries also captured use of "rescue" laxatives, stool consistency, degree of straining for each bowel movement, abdominal pain, and bloating. Researchers also collected data on the participants' diet and physical activity at clinical visits at the beginning and end of the study. Half of the participants also provided stool samples at these visits.
Pro-placebo
At the start of the study, the mean number of CSBMs per week in the probiotic group was 0.73, which rose to 1.58 at the end of the study. While that looked like an improvement, the benefit was flushed away with the finding that the placebo group saw a similar improvement, going from a mean of 0.81 to 1.5 in the study. There was no statistical difference in complete spontaneous bowel movements between the groups, and the researchers concluded the increases in both groups were a placebo effect. Likewise, when the researchers just looked at (incomplete) spontaneous bowel movements and non-spontaneous bowel movements, they also found no statistical differences between the groups.
For individual symptoms of constipation, the groups had no statistically significant difference in stool consistency or straining. Bloating and abdominal pain were low in both groups at the beginning of the study but increased slightly in the placebo group by the end of the study, leading to a slim difference in the two groups. Overall assessments of patient constipation symptoms and quality of life scores found no statistically significant differences between the groups.
Tests from the stool samples also failed to find any significant differences. There was little change during the trial and no significant group differences in the moisture content of stools, or levels of short-chain fatty acids and calprotectin, a marker for intestinal inflammation. Analyses of fecal microbiota composition found that the participants taking the probiotic had a spike in the probiotic strain HN019 but otherwise revealed no significant changes in microbial composition or diversity over the course of the study or between groups.
"While this could align with the observed lack of efficacy of HN019, it is also commonly observed that probiotics do not change the microbiota composition in healthy adults," the researchers noted in their conclusion.
Fermented failures
Overall, daily intake of the probiotic bacteria did not improve the participants' functional constipation—which may not be surprising if you've followed the history of Activia.
In 2010, the Federal Trade Commission and 39 state attorneys general announced a $21 million settlement with Dannon over, in part, the false claim that Activia could treat irregularity. In its marketing—memorable for including a television commercial with actor Jamie Lee Curtis—Dannon indicated that Activia's gut benefits were backed by data. But they were not. In the settlement, Dannon agreed to drop the unsupported health claims. The company also paid $45 million to settle a class-action lawsuit over the false advertising.
Dannon still sells Activia products, making the softer claim that they "help support gut health." For this claim, Dannon has pointed to two studies on its B. lactis substrain.
The first study, published in 2009, included 197 women with minor digestive symptoms and found that those who consumed two servings of the company's probiotic yogurt each day for four weeks reported improvement in symptoms, such as abdominal pain, bloating, and gas. But, then the company repeated the same trial with a larger number of participants—324—and the benefit disappeared.
The second study Dannon points to is an analysis from 2013, which pooled the data from the small successful trial and the larger failed trial and reported an overall benefit. In that analysis, Dannon scientists report that the larger trial failed to show a benefit from the probiotic because the placebo group also reported improvement, a placebo effect echoed in the new JAMA Network Open study.
Beth is Ars Technica’s Senior Health Reporter. Beth has a Ph.D. in microbiology from the University of North Carolina at Chapel Hill and attended the Science Communication program at the University of California, Santa Cruz. She specializes in covering infectious diseases, public health, and microbes.
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