Data doesn’t match the hype for this popular nutritional supplement

Probiotics have been widely touted as the next nutritional panacea for disease prevention. Plenty of people refer to them as the “good” kind of bacteria—live microorganisms that aid digestive health and boost the immune system, among plenty of other purported benefits. But “good” is a relative term—one that isn’t necessarily supported by science.

While the hype related to probiotics is relatively recent, these bacteria have been on scientists’ radar for quite some time. Found in fermented foods and cultured dairy products like yogurt, they were first identified in the early 1900s as one of the microorganisms responsible for fermentation, a process in which sugars are broken down by bacteria and yeast. The beneficial health properties and therapeutic uses of fermented foods have been recognized for centuries, with many early civilizations regarding fermented foods and beverages as a kind of magical elixir.

Over time, probiotics have taken on a similarly mythical health reputation, which has helped them win over American consumers. A National Health Interview Survey found that more than 5 million US adults use probiotics, and the global probiotics industry was worth more than $46 million in 2019, according to Zion Market Research.

Walk into virtually any supermarket or drug store and you’re likely to find an aisle full of probiotic supplements available in pill, powder, and drink form, which often tout long lists of health benefits. Proponents argue that they help protect your gut microbiome by filtering out the “bad” microbes. But despite the popularity of probiotics, the research hasn’t quite caught up to the bold health claims.

What do the experts say?

According to many experts, the jury is still out in the case of probiotics. A 2019 review published in the European Journal of Clinical Nutrition concluded that “the feasibility of probiotics consumption to provide benefits in healthy adults requires further investigation.”

This matches the general consensus of experts in the scientific community. “The current evidence does not convince me to recommend probiotics for any of my healthy patients,” said Pieter Cohen, MD, an assistant professor at Harvard Medical School and an internist at Cambridge Health Alliance, in an interview with The New York Times. Indeed, little is known about the long-term safety of consuming high amounts of probiotics.

New treatment guidelines from the American Gastroenterological Association (AGA) suggest that these bacteria don’t do much for our gut health after all. The report confirmed that there is not sufficient data to support the hypothesis that probiotics can effectively help manage gastrointestinal disorders. Specifically, the AGA analyzed probiotics in relation to Clostridioides difficile associated diseases, inflammatory bowel disease, irritable bowel syndrome, infectious gastroenteritis, and necrotizing enterocolitis. According to the study authors, major knowledge gaps exist in the research of probiotics due to limitations in the quality of available studies and variability in the probiotic strains they studied.

A 2020 study published in Frontiers in Microbiology cast serious doubts on whether probiotic consumption can bring health benefits. The research team subjected probiotics to pH levels similar to those within the body and found that probiotic bacteria grew poorly in these acidic environments, and performed even worse in the presence of bile salts. According to the study’s authors, “probiotic supplements may not only be ineffective, they may also be counterproductive and even detrimental, considering the clinical risk and escalating reports of antibiotic resistance globally.”

Benefits of probiotics

Some clinical studies suggest that probiotics may provide benefits in specific health contexts. For example, the American College of Gastroenterology states that two probiotic strains, Saccharomyces boulardii and Lactobacillus rhamnosus GG, can reduce the risk of diarrhea in adults taking antibiotics.

A 2020 guide published by the Alliance for Education on Probiotics shares a list of functional foods with probiotic strains and cites the clinical support in their favor. One of the functional foods listed in the chart is Activia yogurt, with constipation relief listed as a benefit. A 2016 randomized trial of 60 pregnant women suffering from constipation found that consuming 300 g a day of probiotic yogurt indeed resulted in improved symptoms of constipation.

Finally, at the 2017 annual symposium organized by the University Medical Center Groningen in the Netherlands, a panel presented a hypothesis that probiotics may be used to modulate the maternal microbiome during pregnancy and optimize the development of the fetal microbiome. However, the panel noted that further studies on the maternal microbiome would be necessary to confirm their ideas.

Should you recommend probiotics?

Experts agree that additional research and clinical trials are needed to evaluate the true efficacy of probiotic strains in altering the microbiome. Further research will also help illuminate how different microorganisms help relieve clinical symptoms associated with particular diseases. Scientists and physicians appear to be optimistic that they might confirm the health benefits of probiotics and other “good” bacteria.

For those consuming probiotics, it’s important to note that probiotic supplements are not regulated the same way that the Food and Drug Administration regulates drugs—this means that the messaging on probiotic packaging doesn’t necessarily reflect what’s contained inside. A team of researchers from the Foods for Health Institute at the University of California, Davis found this to be the case when they evaluated 16 probiotic products to determine if their contents actually contained the bacteria species advertised on the labels. Results showed that only one out of the 16 products was precise in its ingredient list.

Until more is understood about the health benefits or drawbacks of probiotics, recommendations on dosage, and who can benefit from the bacteria remains unknown. In the meantime, the best bet to nourish your gut is maintaining a healthy diet.