Key Takeaways

  • People should work with a healthcare provider to understand which probiotics might be helpful, especially those living with a disease or condition.
  • Probiotics might not offer any results because they are unregulated, might not contain enough bacteria, or the bacteria could die before reaching the lower digestive system.
  • Some research shows probiotics might cause more symptoms or even prolong certain health conditions.

The gut microbiome is a complex community of living organisms, including bacteria, viruses, and fungi. Probiotics are living bacteria that may affect the gut microbiome when consumed in supplements or certain foods, but they aren’t always effective.

1. Nobody Knows Which Strains to Recommend

The understanding of the gut microbiome is in its infancy. There is some evidence about which strains are helpful in a select few conditions, but that’s it. Every person has a distinct microbiome, and it’s not yet clear how any particular person will respond to various probiotic strains.

It’s possible to try a probiotic for a health condition and discover that it does help. If that does happen, it might not be clear why, how, or whether the results might help other people with a similar condition.

2. Probiotics Are Not Regulated the Same as Medications

The Food and Drug Administration (FDA) considers probiotics dietary supplements. Because they are supplements, there’s no requirement to review probiotics for safety or effectiveness. Statements in probiotic marketing or packaging about their influence on health may lack strong evidence to support them. For that reason, people may not see the health results promised in advertising.

When To Use Caution With Probiotics

Probiotic supplements are thought to be safe for most healthy people. There’s a concern that because a probiotic is a living bacterium, it could cause infections in certain groups of people. This includes:

  • People who are critically ill
  • People who are severely immunocompromised
  • Premature infants
  • People who live with a digestive condition (such as Crohn’s disease, ulcerative colitis, or Clostridioides difficile infection)

A healthcare provider should always be consulted before starting a probiotic.

3. Probiotic Supplements May Not Contain What’s On the Label

Creating a viable probiotic supplement is not a small undertaking. Probiotics are living organisms, so keeping them alive during manufacturing, shipping, and storage isn’t easy.

Some of the live bacteria in the product may die before they reach the consumer. Cell death during transportation or storage means that the number of bacteria listed on the label isn’t what’s actually in the package.

4. Probiotics May Not Survive the Digestive System

To reach the small and large intestines and populate the gut microbiome, the probiotic must survive the upper gastrointestinal tract. The stomach contains gastric juices that may kill the live bacteria in a probiotic, making it ineffective.

After making it through the stomach alive, the probiotics must now live through the bile in the small intestine. Different bacterial strains have varying tolerances to bile, so some may survive while others die.

Probiotic manufacturers take steps to ensure the live bacteria survive the upper digestive system and reach the lower digestive system. One way to protect the living organisms is to encapsulate them with a coating that won’t break down until it reaches the lower digestive system.

5. Probiotics May Not Help After Taking Antibiotics

Healthcare providers may recommend that people take a probiotic after completing a course of antibiotics for an infection. Antibiotics kill not only harmful bacteria but also beneficial ones. It’s not yet known how to select a specific probiotic that will work well to recolonize the gut for any particular person.

One small study found that, in most cases, probiotics taken after a course of antibiotics didn’t restore the gut microbiome. People taking probiotics actually spent more time with an unbalanced microbiome (called dysbiosis) than those who didn’t.  

What to Look for In a Probiotic

The news on probiotics isn’t all bad. There are some conditions where a probiotic might be helpful. If a probiotic is recommended, here’s what to look for:

  • Ask your healthcare provider for a recommendation.
  • Look for published evidence or clinical trials showing which strains of bacteria may be helpfu.l
  • Look for a probiotic in a form that you are actually going to take (i.e., don’t get a capsule if you struggle to swallow pills).
  • Make sure that you can use all the products you buy before their expiration date.
  • The number of bacteria in a product is measured in colony-forming units (CFUs), and while higher CFUs don’t mean the product is more effective, the CFUs should be in the millions or higher.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Tufts University School of Medicine. Are probiotics all they’re cracked up to be?

  2. Thomme GV and Blackburn KB. Should you take a daily probiotic supplement? MD Anderson Cancer Center.

  3. Sniffen JC, McFarland LV, Evans CT, Goldstein EJC. Choosing an appropriate probiotic product for your patient: An evidence-based practical guide. PLoS One. 2018;13(12):e0209205. doi:10.1371/journal.pone.0209205

  4. Su GL, Ko CW, Bercik P, et al. AGA clinical practice guidelines on the role of probiotics in the management of gastrointestinal disorders. Gastroenterology. 2020;159(2):697-705. doi:10.1053/j.gastro.2020.05.059

  5. Terpou A, Papadaki A, Lappa IK, Kachrimanidou V, Bosnea LA, Kopsahelis N. Probiotics in food systems: Significance and emerging strategies towards improved viability and delivery of enhanced beneficial value. Nutrients. 2019;11(7):1591. doi:10.3390/nu11071591

  6. Wendel U. Assessing viability and stress tolerance of probiotics-a review. Front Microbiol. 2022;12:818468. doi:10.3389/fmicb.2021.818468

  7. Suez J, Zmora N, Zilberman-Schapira G, et al. Post-antibiotic gut mucosal microbiome reconstitution is impaired by probiotics and improved by autologous FMT. Cell. 2018;174(6):1406-1423.e16. doi:10.1016/j.cell.2018.08.047

Amber J. Tresca

By Amber J. Tresca

Tresca is a writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.

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