Probiotics are available in many different species and strengths. Some studies suggest probiotics may help with certain types of diarrhea, but others indicate they have little effect.

Probiotics are live microorganisms, such as bacteria and yeasts, that have some kind of positive effect on the body. Scientists are working to learn more about how probiotics benefit health and how they interact with the human microbiome.

The Food and Drug Administration (FDA) has not yet approved probiotics as a treatment for any health condition, including diarrhea.

This article examines whether people should use probiotics for diarrhea. It also discusses which types of probiotics could be beneficial, who can take them, and the potential side effects and risks.

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Diarrhea has many causes, and each person’s microbiome is unique. Whether a probiotic helps with diarrhea may depend on a person’s specific situation.

Acute infectious diarrhea

Acute diarrhea is when a person experiences three or more loose stools daily, lasting less than 2 weeksTrusted Source. Infections are one of the most commonTrusted Source causes of acute diarrhea.

An older 2010 Cochrane review assessed 63 previous trials involving 8,014 participants. It found that probiotics reduced the duration of diarrhea by approximately 25 hours in comparison to control groups.

Probiotics also decreased the risk of diarrhea lasting for 4 days or more by 59% and resulted in one fewer loose stools 2 days after taking them.

However, when Cochrane updated the review in 2020, with evidence from 82 studies with 12,127 participants, the authors reached the opposite conclusion.

They used larger trials with a lower risk of bias than the first review. They concluded that probiotics likely make little or no difference to the risk of diarrhea lasting more than 48 hours and that the evidence for probiotics shortening the duration of diarrhea was weak.

Antibiotic-induced diarrhea

Around 5–25%Trusted Source of adults taking antibiotics experience diarrhea as a side effect due to their impact on the microbiome. One of the most commonTrusted Source causes is Clostridium difficile, which accounts for around 20–30% of cases.

According to the Office of Dietary SupplementsTrusted Source, some probiotics, such as Saccharomyces boulardii, may decrease the risk of antibiotic-related diarrhea in individuals younger than 65 years, but not older adults. These probiotics may be beneficial when people take them within 2 days of their first antibiotic dose.

A 2021 study found that compared with a placebo, yogurt containing the probiotic Bifidobacterium lactis BB-12 helped protect against changes in gut bacteria that can lead to antibiotic-induced diarrhea.

Traveler’s diarrhea

Traveler’s diarrhea is a common illness people can get when traveling abroad. A 2018 meta-analysis of 11 studies concluded that probiotics may significantly reduce the risk of travelers’ diarrhea, but a 2019 review of 12 studies found that only S. boulardii CNCM I-745 was particularly effective.

However, the authors noted that more research was necessary to explore probiotic strains and their effect on traveler’s diarrhea.

If a person has one of the above conditions that cause diarrhea, the following species of probiotic could have a positive effect:

  • S. boulardii: This beneficial species of yeast has evidence supporting its use for traveler’s diarrhea and antibiotic-related diarrheaTrusted Source.
  • Lactobacillus: L. rhamnosus, L. casei, and L. acidolphilus have evidence to support their use for antibiotic-associated diarrhea and acute diarrhea.
  • Bifidobacteria: This family of bacteria is often present in dairy products, such as yogurt, which may help reduce the risk of antibiotic-associated diarrhea.

That said, it is important to note that no probiotic is an approved treatment for diarrhea, as scientists are still learning about them. If the symptoms worsen or keep recurring, a person should speak with a doctor.

Probiotics may not be safe for everyone.

For people with no other health conditions, probiotics with a long history of use in foods are typically safeTrusted Source to take, according to the National Center for Complementary and Integrative Health. This includes Lactobacilli and Bifidobacteria species.

However, people with severe illnesses or compromised immune systems should not take probiotics due to the risk of an opportunistic infection.

It may also be unsuitable to take probiotics if a person has certain digestive conditions. For example, a 2018 studyTrusted Source found that people with small intestinal bacterial overgrowth (SIBO) experienced worsened symptoms and brain fog due to taking probiotics.

The researchers advise proceeding with caution if a person:

In its 2020 guidelines, the American Gastroenterological Association also recommends against using probiotics for acute infectious diarrhea in children.

When trying probiotics, it is important to consider:

Dosage

Companies list the dosage of their probiotics in colony-forming units (CFUs). Probiotic supplements usually contain 1–10 billion CFU per doseTrusted Source, but some can be much stronger. A higher CFU does not necessarily mean the product is better or that it will be more effective.

Studies investigating the effect of probiotics on diarrhea have CFU ranging between 10–100 billion CFU per dose. A healthcare professional can help an individual select the most appropriate probiotic strain and dosage.

Some people prefer to start with a low dose and work up to the recommendation from a doctor or the product label.

Timing

In some situations, the timing of probiotic doses may influence their effectiveness.

For example, evidence suggests that people with antibiotic-associated diarrhea benefit most when they start probiotics within 2 daysTrusted Source of their first dose of antibiotics. Taking them away from the antibiotics may help prevent the antibiotic from killing the “good” bacteria.

If a person is traveling somewhere where there is a high risk of traveler’s diarrhea, they may choose to begin taking a probiotic that is proven to help prevent it shortly before arrival.

Any side effects of probiotics are typically mildTrusted Source and may include gas, bloating, or digestive changes.

If symptoms significantly worsen or keep returning, this may not be due to the probiotics. Anyone with the following symptoms should speak with a doctor:

Research examining the use of probiotics for diarrhea have conflicting results. Some studies suggest that certain probiotics may be helpful for specific causes of diarrhea. Other studies have concluded that probiotics probably have little to no effect.

If a person wants to try probiotics for diarrhea, it is important that they consult a doctor to determine the cause. In some cases, the cause may be unrelated to gut bacteria, and probiotics may not be necessary.

A person should seek medical attention if they have recurring or severe diarrhea.