Probiotic Use for Diarrhea

No doubt about it, probiotics are a big seller and research into the human microbiome suggests that the bacteria in our GI tract is having potentially profound effects on health and disease.  Researchers have made progress recently in identifying the particular strains of probiotic that provide relief of diarrhea.

What Are Probiotics

Probiotics are live microbes (bacteria or yeast) that are intended to have health benefits. Many believe that probiotics can improve digestive issues and may help balance the gut microbiome. Probiotics are not to be confused with “prebiotics”, which refer to fiber substances that the probiotic microbes eat.  In other words, prebiotic (think fiber) feeds the probiotic microbes. 

A Million Strains-Each One With Different Effects

Most people talk about “probiotics” as though they are one thing.  For example, “Doctor, should I take probiotics?”  The problem is that there are huge families of probiotic strains-like Lactobacillus and Bifidobacterium that are each made up of a huge number of individual strains of organisms.  Each probiotic product has its own single strains or blend of strains.  Each product will then have its own individual effects depending on the specific condition it’s being used for. 

And that’s not all.  When it is taken into account that each human being has their own unique mixture of trillions of gut bacteria, it makes perfect sense that a probiotic that works in one person may not have the same effect for someone else.

Research on Probiotics for Diarrhea 

Diarrhea has several major causes including antibiotics, food poisoning, flu, and cancer treatment.  Often, it will resolve within 3 or 4 days without any treatment, but can be serious when it is associated with dehydration.  Many different probiotic strains or combinations have been studied and some have been found to help.   But there are still questions on which ones are effective and how safe they really are for some individuals. 

Antibiotic-Associated Diarrhea

Antibiotics kill off large swaths of the population of a healthy gut microbiome, so it’s no wonder that diarrhea results.  Many patients will develop diarrhea, and for some, it can last months after antibiotics have been stopped.

Some studies have shown that probiotics seemed to work better in younger populations to reduce antibiotic-associated diarrhea.  Seniors tend to have more common antibiotic associated diarrhea, including a severe type of diarrhea related to a particular strain of bacteria called Clostridium Difficile or C. diff.  1

The Best Strains for Decreasing Diarrhea

A review from 2017 found that taking probiotics during antibiotic treatments was associated with about half the incidence of antibiotic associated diarrhea.  They found that the most effective strains were L rhamnosus GG and S boulardii2

Probiotics for Food Poisoning and “Stomach Flu”

Bacteria, viruses, and parasites can cause inflammation in the stomach and intestines that results in diarrhea.  Research on probiotics has shown that Lactobacillus reuteri was able to lessen the duration of this type of diarrhea by about a day. 3

Diarrhea and Cancer Treatment

Many types of chemotherapy and radiation therapy damage the digestive tract and diarrhea is a very common result.  Research has been done on different strains and doses of probiotics, but reviews were not able to find definite evidence of benefit. 4

Irritable Bowel Syndrome (IBS)

IBS is a group of symptoms including bloating, abdominal pain, diarrhea, constipation, or a combination of these.  It affects about 1 in 10 people and is more common in women.

Recently, several strains have been found to make a difference for IBS. 5 The following strains have been found to be effective in randomized trials:

  • B. longum 35624 is the probiotic strain in the products Align®, Align® Chewables, and Align® Extra Strength.
  • L. plantarum 299v is the strain in Ideal Bowel Support®, UltraFlora® Intensive Care and GoodBelly®.
  • Bio-Kult® is a mixture of 13 different strains of probiotic.

Probiotics Are Generally Safe, but Can Have Side Effects

It’s important to note that while probiotics are safe for most healthy people, they are generally unregulated just like vitamins and herbal supplements. Elderly and immune compromised should weigh the risk of side effects.  These can include changes in bowel habits and bloating. 

Probiotics can also change the gut microbiome in ways that have not been studied, and may have unknown risks.

Each Person May Have a Different Result

With each person having their own unique microbial population, each person’s response to a probiotic strain may be different.

Probiotic Potency

Dosage for probiotics are measured in billions of cells, or “cfu” – colony forming units. The age of the bottle will have an effect on how many of the original billions of cells are still alive and able to colonize the gut.

Storage Conditions will also have an effect on the viability of the organisms, and it is not clear whether refrigerated storage is always an advantage for the product’s potency.

Take-Away Messages From the Research: 

  • Antibiotic Associated Diarrhea- the most effective strains were L rhamnosus GG and S boulardii and they seemed to improve the diarrhea by about 50%.
  • For IBS, longum 35624 and L. plantarum 299v as well as the Bio-Kult® probiotic combination have been effective in randomized trials.
  • For Diarrhea related to Cancer Treatments, there was no definite evidence that show probiotics provide a benefit.

Consider How a Dietitian May Be Able to Help

Diarrhea can range from a mild, “once-in-a-while” nuisance to a debilitating problem that keeps a person imprisoned at home for fear of bowel accidents. Chronic diarrhea can have a huge range of causes including Celiac, Irritable Bowel, and Small Intestinal Bacterial Overgrowth–all of which require specific nutritional approaches that can be confusing and complex to make happen in your life.

When diarrhea is affecting your quality of life, it’s time to seek professional help. Consider consulting a gastroenterologist to rule out some medical causes like Crohns, Ulcerative Colitis, and Chronic Pancreatitis.

Celiac can be ruled out with a blood test. Many causes of diarrhea can be highly responsive to changes in the foods you choose.

Dietitians specializing in digestive health can help you work through the mystery of your digestive symptoms and the myriad components of your ever-changing diet to come up with strategies that will improve your quality of life.

You can search for a dietitian specializing in digestive health on NutriScape.NET’s Telenutrition Site.

affiliate statement

Products that may help

It’s easy to see that probiotic supplements are no panacea. Probiotic foods are another option. Dietitians generally recommend that a product be taken for about 3 weeks in order to see if it works. To obtain products noted above, visit this page.

Notice: The NutriScape.NET site is intended for educational purposes and does not constitute the practice of health care advice, diagnosis, or treatment. Individuals should seek the advice of a qualified healthcare provider for any questions regarding personal health or medical conditions. Access to independently licensed Registered Dietitian Nutritionists can be found through our Telenutrition site.


  1. Jafarnejad S, Shab-Bidar S, Speakman JR, Parastui K, Daneshi-Maskooni M, Djafarian K. Probiotics reduce the risk of antibiotic-associated diarrhea in adults (18-64 years) but not the elderly (>65 years): a meta-analysis. Nutr Clin Pract. 2016;31(4):502-513.)
  2. Blaabjerg S, Artzi DM, Aabenhus R. Probiotics for the prevention of antibiotic-associated diarrhea in outpatients—a systematic review and meta-analysis. Antibiotics (Basel). 2017;6(4):E21.
  3. Patro-Gołąb B, Szajewska H. Systematic review with meta-analysis: Lactobacillus reuteri DSM 17938 for treating acute gastroenteritis in children. An update. Nutrients. 2019;11(11):E2762.
  4. Wei D, Heus P, van de Wetering FT, van Tienhoven G, Verleye L, Scholten RJ. Probiotics for the prevention or treatment of chemotherapy- or radiotherapy-related diarrhoea in people with cancer. Cochrane Database Syst Rev. 2018;8:CD008831.
  5. Clinical Guide to Probiotic Products Available in USA- 2020 Edition.

About the Author

Stephanie Figon, MS, RDN, LD

Founder of NutriScape.NET. As a dietitian since 1992, Steph Figon has had experiences in consulting, 15 years in clinical, and has operated a private practice nutrition counseling office for since 2011. Connect on Linkedin