An advanced guide to 

Exploring probiotics
for gut health

Bacteria are often thought about in the context of illness, but our body is home to trillions of bacteria that contribute to our overall health and wellbeing. Probiotics are live bacteria that are beneficial to our health, especially to our gut health. These friendly bacteria help keep our digestive system running smoothly, help our immune system defend against pathogens, and can have effects on everything from our mood to our sleep.

Although probiotics are now available as supplements, it’s important to note that probiotic strains differ in their health benefits. Below is a guide to some probiotic strains that have shown a benefit in human health.

Lactobacillus group

Lactobacillus strain
Potential applications based on research:

L. acidophilus

Diarrhea, constipation, vaginal health

L. rhamnosus

GI infections, diarrhea, irritable bowel syndrome

L. plantarum

Inflammatory bowel disease, irritable bowel syndrome

L. casei

Diarrhea, anxiety

L. acidopilus

As one of the most widely known probiotics, the consumption of L. acidophilus in medicine can be traced back to the 1920s when doctors would recommend acidophilus-containing milk for constipation and diarrhea. One of the earliest human studies, in 1922, investigated L. acidophilus in 30 patients with chronic constipation, diarrhea, or eczema and found improvements for all three conditions.1

While some probiotic strains can be rapidly killed in the stomach, L. acidophilus can pass through the whole gut at high concentrations.2

Some studies suggest that L. acidophilus may be helpful in treating vaginal infections, while others show that it may be helpful in the prevention and treatment of diarrhea, and may be a beneficial addition in the treatment of colorectal cancers.3,4,5

L rhamnosus

L. rhamnosus is a widely used probiotic strain and one of the most extensively studied probiotics in adults and children.3,6 Various health effects from its use are documented, including the prevention and treatment of gastrointestinal infections and diarrhea, and the stimulation of immune responses.3,6

Findings from research studies


L. rhamnosus may be beneficial in:

  • The prevention of rotavirus diarrhea in children, and the prevention and treatment of various types of diarrhea in children and adults.7,8,9
  • The prevention of antibiotic-associated diarrhea.10,11,12
  • Reducing the risk of traveler’s diarrhea.13

Acute gastroenteritis

A paper published by ESPGHAN Working Group for Probiotics and Prebiotics based on a systematic review of randomized controlled trials (RCTs) suggested that L. rhamnosus may be considered in the management of children with acute gastroenteritis in addition to rehydration therapy.14

Irritable bowel syndrome

L. rhamnosus may reduce:

  • The symptoms of diarrhea-predominant (IBS-D) irritable bowel syndrome.15
  • Intestinal permeability in children who suffer from irritable bowel syndrome.15

Respiratory tract infections

L. rhamnosus may reduce the risk of respiratory tract infections in a daycare setting.16,17

L. plantarum

The use of L. plantarum has been shown to help regulate immunity and control inflammation. A 2007 study found that the probiotic could suppress an inflammatory response in the gut, and a double-blind, placebo-controlled study over four weeks concluded that L. plantarum provided effective symptom relief, especially of abdominal pain and bloating, in patients with irritable bowel syndrome.18

Findings from research studies

Inflammatory bowel disease

The effect of L. plantarum on IBD has been investigated in several in vitro studies which showed it improved immune response.19

Irritable bowel syndrome

L. plantarum may reduce the symptoms of irritable bowel syndrome.20 One study found that after four weeks with L. plantarum treatment, 78% of the patients scored the probiotic as good or excellent for improving symptoms, particularly for pain and bloating.18

L. casei

Studies have shown some promising results with L. casei for digestive support and regulating diarrhea. One study on the effect of milk fermented by a L. casei strain showed that supplementation significantly reduced the incidence of diarrhea.21

Surprisingly, L. casei has also been shown to be beneficial in relieving anxiety. In a randomized, double-blind, placebo-controlled study, supplementation with L. casei led to a rise in Lactobacillus and Bifidobacterium, as well as a significant decrease in symptoms of anxiety and depression.22

L. casei has been combined with other probiotic strains of bacteria in randomized trials studying its effects in preventing antibiotic-associated diarrhea (AAD) and Clostridium difficile (CDI) infections. Treated patients in these trials had significantly lower rates of AAD or CDI compared to placebo.23 Additionally, trials have shown significantly shorter recovery times in the L. casei treatment group compared to placebo in children suffering from acute diarrhea primarily caused by rotavirus.24

Findings from research studies


L. casei may be beneficial in:

  • Reducing the incidence of diarrhea.21,24
  • Lowering the rates of AAD.23
  • Lowering the rate of CDI.23


In a randomized, double-blind, placebo-controlled study, supplementation with L. casei led to a rise in Lactobacillus and Bifidobacterium, as well as a significant decrease in symptoms of anxiety and depression.22

Bifidobacterium group

Bifidobacterium strain
Potential applications based on research

B. animalis

Immunity, digestion, ulcerative colitis

B. longum

Immunity, constipation, ulcerative colitis, irritable bowel syndrome, stress

B. bifidum

Immunity, irritable bowel syndrome, H. pylori infection

B. breve


B. animalis (also known as B. lactis)

B. animalis has been shown across multiple studies to improve immune function. One study found a greater immune response to influenza vaccine among those taking B. animalis compared to placebo, with the author concluding that this probiotic may help improve immune function.25 Another study found that supplementation with B. animalis led to self-reported improvements in digestive comfort.26

Findings from research studies

General immunity

B. animalis may be beneficial in boosting general immunity.25

Digestive discomfort

In an open label, randomized, controlled trial, participants who consumed fermented milk containing B. animalis reported improved digestive comfort.26

B. longum 

This is one of the first types of bacteria to colonize our gastrointestinal tracks after we are born. B. longum, along with other Bifidobacterium species, represent up to 90% of the bacteria of an infant’s gastrointestinal tract.27 While B. longum is not significantly present in the adult gastrointestinal tract, it is considered a resident of the gut microbiome and its production of lactic acid is believed to prevent growth of gut pathogens.28 Its potential benefits include boosting general immunity, relieving constipation, and helping address symptoms of ulcerative colitis and irritable bowel syndrome.

Findings from research studies

General immunity

In one study, the use of B. longum was shown to shorten the duration and minimize the severity of cold symptoms.29


In a randomized, double-blind, placebo-controlled trial, participants who consumed cereal containing B. longum had a statistically-significant increase in bowel movements.30

Ulcerative colitis

In one study, B. longum reduced ulcerative colitis symptoms in Japanese patients.31

Irritable bowel syndrome

B. longum may reduce intestinal inflammation and was shown to relieve IBS symptoms in a clinical study.32


A study from University College Cork found in a study of healthy men that taking a B. longum supplement lead to decreased stress levels and improved memory.33

B. bifidum

Researchers have found that B. bifidum may help regulate the innate immune response, your body’s first line of defense against infection.34 This regulation may be why the probiotic strain has been shown to help address symptoms in H. pylori  infections and address symptoms of irritable bowel syndrome.35,36

Findings from research studies

General immunity

The findings of one European study suggest that B. bifidum modulates our innate immune response, reducing inflammation while simultaneously stimulating our immune system.34

Irritable bowel syndrome

In a 2011 study, researchers reported that those receiving B. bifidum showed a significant reduction in IBS symptoms and a significant improvement in their overall quality of life, compared with those who received placebo.36

H. pylori infection

In one study, B. bifidum improved rates of upper gastrointestinal symptomatic subjects and total symptoms in patients with H. pylori infections.35

B. breve

A pilot study found that B. breve was effective in increasing stool frequency in children with constipation. These researchers also found a positive effect in stool consistency and relief in abdominal pain.37

next article

Probiotics for specific conditions

The use of probiotics to address different conditions is still in an exploratory research phase, but there have been some promising findings.

Read Article

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