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How Probiotics Can Benefit Gut Health

Written by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

Probiotics may help prevent and manage a variety of gut disorders and complaints, from diarrhea to IBD to gastric ulcers. Which species have been tested, and which one could be right for you? Read on to learn more.

Probiotics & Gut Health

Probiotic supplements are currently under investigation for their potential to improve a number of digestive conditions and complaints. This should come as no surprise, given the important of the gut flora to human health and well-being. As we’ve explored in other posts, the bacteria that live in our intestines have far-reaching consequences for our health.

But without going that far, without even leaving the intestines, what benefits could probiotics have? In this post, we’ll discuss the potential of good bacteria to improve digestive health, but they may not be right for everyone; remember to talk to your doctor before adding any new supplement to your regimen.

Likely Effective For

1) Diarrhea

Use of probiotics in antibiotic-associated diarrhea decreased the risk of diarrhea by 52%, traveler’s diarrhea by 8%, and acute diarrhea from various causes by 34%. Probiotics were more effective in reducing the risk of acute diarrhea in children 57% versus 26% in adults [1].

Acute Infective Diarrhea

L. casei reduced the incidence, duration, and severity of diarrhea in children [2, 3].

L. paracasei effectively resolved acute diarrhea [4] and ameliorated non-rotavirus-induced diarrhea in children [5].

L. acidophilus reduced the duration of diarrhea in hospitalized, but not outpatient, children [6], and ameliorated both rotavirus-positive diarrhea [7] and rotavirus-negative diarrhea in children [8].

L. acidophilus and B. bifidum shortened the duration of diarrhea in infants and children [9].

L. rhamnosus administration was associated with significantly lower rates of and symptomatic rotavirus gastroenteritis diarrhea in hospitalized children [10].

L. reuteri decreased the incidence of diarrhea in children [11].

Formula supplemented with B. bifidum and S. thermophilus reduced the incidence of acute diarrhea and rotavirus shedding in infants admitted to hospital [12].

B. breve together with S. thermophilus reduced the severity of acute diarrhea and dehydration among healthy young infants [13].

B. animalis spp. lactis milk formula prevents diarrhea in infants and decreased diarrhea frequency and duration [14, 15, 16].

S. boulardii significantly reduced the frequency and duration of acute diarrhea in children [17, 18, 19, 20, 21, 22, 23, 24]. It also often reduced the length of ECU and hospital stay in acute infectious gastroenteritis in children [25, 26].

S. boulardii also decreased the duration and frequency of diarrhea and ameliorated abdominal pain in adults [27]; it shortened the length of hospital stay in patients with acute infectious diarrhea [28].

Certain probiotics—especially Lactobacillus, Bifidobacterium, and Saccharomyces species—reduced the duration and severity of diarrhea caused by infectious bacteria in infants, children, and adults.

Antibiotic-Associated Diarrhea

Treatment with L. rhamnosus reduced the risk of antibiotic-associated diarrhea (AAD) in patients treated with antibiotics from 22.4% to 12.3% [29].

L. casei intake was associated with a decreased risk of antibiotic-associated diarrhea [30, 31].

L. helveticus and L. rhamnosus supplementation significantly reduced the duration of antibiotic-associated diarrhea in healthy adults receiving antibiotics [32].

B. animalis spp. lactis together with S. thermophilus reduced the frequency of antibiotic-associated diarrhea (AAD) in infants [33].

Concomitant administration of C. butyricum with antibiotics normalized the intestinal microbiota, prevented the decrease of Bifidobacteria, and effectively prevented and improved antibiotic-associated diarrhea in children [34].

Some studies report that S. boulardii is not effective in preventing the development of antibiotic-associated diarrhea [35, 36, 37, 38]. However, many studies demonstrate that S. boulardii effectively reduced the risk of antibiotic-associated diarrhea in both children and adults [39, 40, 41, 42, 43, 44, 45].

B. subtilis significantly reduced the incidence of antibiotic-associated diarrhea and prevented nausea, bloating, vomiting and abdominal pain [46].

Probiotics have also effectively prevented or reduced diarrhea caused by antibiotics in children and adults.

Traveler’s Diarrhea

S. boulardii may prevent traveler’s diarrhea, particularly in regions such as North Africa and in the Near-east [47].

Chemo- and Radiotherapy-induced Diarrhea

Probiotics may have a beneficial effect on the prevention of chemo- and radiotherapy-induced diarrhea, where they rarely cause adverse effects [48].

See individual probiotic posts for more information and animal studies.

2) Necrotizing Enterocolitis

Necrotizing enterocolitis is an infection of the intestines of premature babies. If untreated or treated too late, it is frequently lethal [49].

Oral supplementation of L. paracasei reduced the clinical progression of necrotizing enterocolitis in infants [50].

Prophylactic L. acidophilus and B. infantis reduced the incidence and mortality of necrotizing enterocolitis (NEC) in infants [51].

B. breve was associated with decreased risk of necrotizing enterocolitis in neonates [52].

Oral administration of B. breve reduced the production of butyric acid in infants, which may be helpful in protecting low birth weight infants from digestive diseases such as necrotizing enterocolitis [53].

However, one study found no benefit in B. breve administration for the prevention of necrotizing enterocolitis and late-onset sepsis in very preterm infants [54].

B. breve suppressed inflammation, reduces the pathology and increases survival in rats with necrotizing enterocolitis [55].

Probiotics show promise in both preventing and supporting the treatment of necrotizing enterocolitis in preterm babies.

Possibly Effective For

3) Discomfort & Well-being

Probiotics can decrease the number of potentially pathogenic gastrointestinal microorganisms and pathogens, reduce gastrointestinal discomfort, flatulence and bloating, and improve bowel regularity [56].

B. animalis spp. lactis improved digestive comfort and GI symptoms in healthy adults [57, 58].

Probiotic fermented milk containing B. animalis spp. lactis by healthy women may improve GI well-being and decrease the frequency of GI symptoms [59, 60, 61].

4 weeks’ supplementation with B. animalis ssp. lactis resulted in a clinically relevant benefit on defecation frequency in healthy adults with abdominal discomfort [62].

Ingestion of B. bifidum significantly decreased the prevalence of gastric and lower abdominal symptoms in adults taking no medication [63].

Administration of L. helveticus to healthy human subjects resulted in a significant increase in butyrate, beneficial for gut homeostasis [64].

Probiotics promoted gastric mucus secretion [65] and B. bifidum alleviated acute gastric injury by enhancing the production of gastric mucin in rats [66].

Probiotic supplements have improved digestive comfort, regulated bowel movements, and decreased GI distress in human trials.

4) Modifying Gut Microbiota

Probiotics, in general, tend to increase the levels of Lactobacilli and Bifidobacteria in the gut, while decreasing the levels of potentially pathogenic microorganisms [67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79].

5) Drug-Induced GI Damage

Probiotics maintained healthy intestinal microbiota in subjects receiving antibiotic treatment [56].

L. acidophilus administered with amoxicillin/clavulanate was associated with a significant decrease in patient complaints of GI side effects and yeast superinfection [80].

L. casei is effective for the treatment of aspirin-associated small bowel injury in chronic low-dose aspirin users [81].

Long-term L. rhamnosus supplementation influenced the composition of the intestinal microbiota in children and reduced the frequency of gastrointestinal complaints after antibiotic use, preventing certain bacterial infections for up to 3 years after the trial [82].

L. delbrueckii microcapsules relieved intestinal tissue damage in mice and improved antibiotic-induced intestinal microbiota dysfunction [83].

L. paracasei therapy prevented antibiotic induced visceral hypersensitivity and restored normal gut permeability in rats [84].

L. fermentum normalized the composition of gut microbiota and alleviated ampicillin-induced inflammation in the colon in mice [85].

B. animalis ssp. lactis protected against NSAID-induced GI side effects in rats and may prevent more serious GI mucosal damage and/or enhance the recovery rate of the stomach mucosa [86].

S. boulardii significantly reduced the numbers of gastric ulcers and the ulceration surface of the gastric mucosa in rats treated with ibuprofen [87].

S. thermophilus reduced inflammation and prevented chronic gastritis in aspirin-treated mice [88, 89].

Antibiotics and other drugs can damage the intestines and leave the patient vulnerable to recurrent infections. Probiotic supplements may help accelerate the recovery of the gut after treatment.

6) Constipation

L. paracasei relieved constipation [90].

Heat-killed L. brevis improved intestinal function in women with constipation [91, 92].

L. reuteri improved constipation, increasing the number of bowel movements in adults [93] and infants [94].

B. breve effectively diminished abdominal pain and increased stool frequency in children with functional constipation [95].

B. animalis spp. lactis showed beneficial effects on constipation in human studies [96, 97, 98].

B. coagulans improved constipation symptoms in children [99] and adults [100].

P. freudenreichii relieved constipation in young healthy women [101].

Some researchers believe that a synbiotic regimen of lactulose and live binary B. subtilis could be an effective and safe therapy for elderly with functional constipation [102].

See individual probiotic posts for more information and animal studies.

Lactobacillus and Bifidobacterium probiotics relieved constipation and reduced abdominal pain in children and adults.

7) Irritable Bowel Syndrome

Irritable bowel syndrome appears to cause a reduction in intestinal Lactobacilli and Bifidobacteria [103]. Probiotics improved global IBS symptoms and decrease IBS-associated pain [1].

L. acidophilus reduced abdominal pain and discomfort in patients with irritable bowel syndrome (IBS) [104, 105].

L. plantarum reduced gas problems and pain in people who suffer from irritable bowel syndrome [106].

Probiotics containing L. plantarum and B. breve in IBS patients decreased pain by 38% in the probiotic group compared with 18% in the placebo group. After 28 days, the pain was decreased by 52% in the probiotic group compared with 11% in the placebo group [1].

L. rhamnosus may reduce pain frequency and intensity in children [107] and adults [108] with IBS.

L. rhamnosus may also reduce symptoms in children with functional gastrointestinal disorders [108].

According to one study, L. reuteri may help produce serotonin and lessen susceptibility to gut problems and IBS [109].

L. rhamnosus, L. reuteri and VSL#3 significantly increased treatment success for functional gastrointestinal disorders (FGIDs) in children and adolescents [110].

A mixture of B. infantis, B. breve, and B. longum improve abdominal pain and the quality of life in children with irritable bowel syndrome (IBS) [111].

B. longum ssp. infantis reduced intestinal inflammation and improved abdominal pain/discomfort, bloating/distention, and bowel movement difficulty in patients with IBS [56, 112, 113].

B. bifidum significantly improved reported pain/discomfort, distension/bloating, urgency and digestive disorder in patients with IBS [114].

In one study, fermented milk containing B. bifidum improved symptoms in patients with functional gastrointestinal disorders (FGID). Abdominal pain, diarrhea, and constipation significantly improved, as did acid-related dyspepsia. Psychological symptoms such as anger and hostility also improved [115].

B. animalis had a beneficial effect on discomfort, bloating and constipation in constipation-predominant IBS patients [116].

B. animalis spp. lactis significantly improved objectively measured abdominal girth and gastrointestinal transit, as well as reduced symptomatology in IBS patients [117].

B. coagulans decreased bloating, vomiting, diarrhea, abdominal pain, and stool frequency and increased the quality of life in patients with diarrhea-predominant irritable bowel syndrome (IBS) [118, 119, 120, 121].

A combination of simethicone and B. coagulans reduced bloating and discomfort in patients with IBS [122].

L. brevis improved the quality of life, reduced diarrhea and abdominal pain, and increased Bifidobacteria in patients with IBS [123].

S. boulardii improved the cytokine profile, histology, and the quality of life of patients with diarrhea dominant irritable bowel syndrome (IBS-D) [124] or mixed-type IBS [125].

S. boulardii alone or with mesalazine improved IBS-D symptoms [126]. One study, however, found no improvement in IBS-D patients after S. boulardii treatment [127].

In one clinical trial, S. cerevisiae reduced abdominal pain and discomfort in subjects with IBS [128]. In another trial, however, S. cerevisiae had no beneficial effect on IBS symptoms and wellbeing. However, it seemed to have some effect in the subgroup with constipation [129].

A combination product designated VSL#3, which contains large quantities of 8 bacterial species, was shown to significantly improve IBS symptoms [1].

Probiotic supplements improved the symptoms of both diarrhea and constipation type IBS patients in many clinical trials.

8) Gut Pain

Oral administration of L. acidophilus induced the expression of mu-opioid and cannabinoid receptors in intestinal epithelial cells and mediated analgesic functions in the gut similar to the effects of morphine [130].

B. coagulans + fructooligosaccharide (FOS) decreased abdominal pain duration and frequency in children with GI disorders [131].

A B. coagulans synbiotic improved childhood functional abdominal pain [132].

B. coagulans significantly improved abdominal pain and the quality of life in adults with postprandial intestinal gas-related symptoms and no GI diagnoses [133].

In animal models of gut pain, L. reuteri has been associated with decreased activation of the nervous system and reduced pain [134, 135].

L. reuteri ingestion impacted the nerves in such a way that it may slow gut motility (improving cases of diarrhea) and decrease pain perception [136].

L. rhamnosus may attenuate neonatally induced chronic visceral pain; it significantly altered levels of serotonin, noradrenaline, and dopamine in rats [137].

Probiotics reduced the perception of gut pain (both duration and frequency) in multiple human and animal trials.

Insufficient Evidence For

The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of probiotics for any of the below-listed uses. Remember to speak with a doctor before taking probiotic supplements, and never use them in place of something your doctor recommends or prescribes.

9) Strengthening the Intestinal Barrier

The intestinal barrier separates the contents of the gut from the rest of the body. This barrier prevents the entry of harmful substances such as foreign antigens, toxins, and microorganisms. Hyperpermeability of this barrier (“leaky gut”) may contribute to the pathogenesis of several gastrointestinal disorders including IBD, Celiac disease, and food allergy [138].

In humans, L. rhamnosus protected against disruption of the gastric mucosal barrier [65].

Fermented milk with L. paracasei promoted intestinal epithelial cell growth and intestinal epithelial integrity and strengthened the intestinal barrier against chemical and inflammatory stimuli-induced damage [139].

L. paracasei synbiotic therapy may prevent or repair colon damage in mice with acute colitis, where this bacterium completely restored epithelial barrier integrity [140, 141].

In rats, B. bifidum or B. animalis protected the mucous membrane layer of the stomach [65].

S. cerevisiae strengthened epithelial barrier function [142]. Oral treatment with viable or heat-killed S. cerevisiae strain prevented bacterial translocation, protects intestinal barrier integrity, and stimulated immunity in mice with intestinal obstruction [143].

The intestinal barrier controls which nutrients and other compounds cross from the gut into the bloodstream. In humans and animals, probiotic supplements “tightened up” this barrier and prevented harmful compounds and bacteria from crossing.

10) Gastric Ulcers

According to one review, probiotics inhibited the development of acute gastric mucosal lesions and accelerated gastric ulcer healing in humans and animals [65].

Lactobacilli promoted gastric ulcer healing in rats when administered as an individual probiotic strain, such as L. rhamnosus, L. gasseri, or L. acidophilus or as a probiotic mixture [65, 65, 65, 144, 145, 65].

B. breve and B. bifidum repaired and protected the mucosa of rats against gastric ulcers and erosions [65].

Pretreatment of mice with gastric ulcers with the probiotic C. butyricum alleviated the inflammation and gastric mucosal damage [65].

Certain yeasts, such as S. boulardii and S. cerevisiae have also shown beneficial effects in rats with gastric ulcers [65].

Some probiotic supplements may help prevent development and accelerate healing of gastric ulcers, though human studies are lacking.

11) Inflammatory Bowel Disease

B. longum ameliorated ulcerative colitis symptoms in Japanese patients [146].

S. boulardii added to baseline therapy improved intestinal permeability in Crohn’s disease (CD) patients, even though complete normalization was not achieved [147]. This probiotic also reduced the frequency of bowel movements in CD patients [148].

P. freudenreichii was effective against mild to moderate ulcerative colitis in a human pilot study [149].

In Asian studies involving patients with ulcerative colitis, the addition of a B. subtilis probiotic significantly reduced the number of days with bloody stool, led to complete remission without relapse, and significantly increased the efficacy of mesalazine or sulfasalazine therapy [150].

L. plantarum ameliorated ulcerative colitis in mice via both anti-inflammatory and immunomodulatory activities [151] and decreased the severity of intestinal inflammation in mice with inflammatory bowel disease (IBD) [2].

B. bifidum decreased symptoms of inflammatory bowel disease (IBD) in mice, such as thickened intestinal wall and inflammatory cell infiltration, and decreased inflammatory cytokine production [152].

Other probiotics that were effective in ameliorating colitis in animal models include L. casei [153, 154], L. paracasei [155], L. salivarius [156], L. delbrueckii ssp. bulgaricus [157], L. delbrueckii ssp. lactis [158], L. helveticus [159], B. longum [160], B. animalis ssp. lactis [161, 162, 163], C. butyricum [164, 165, 166], B. coagulans [167, 168], L. brevis [169, 170, 171], L. fermentum [172, 173, 174, 175], S. boulardii [176], L. lactis [177, 178, 179, 180], S. thermophilus [181], P. freudenreichii [74, 182, 183], B. subtilis [184, 185, 186, 187] and S. cerevisiae [188, 189].

B. longum ssp. infantis ameliorated colitis, possibly by decreasing Th1 and Th17 responses [190].

S. thermophilus also repressed the Th17 response to ameliorate intestinal lesions [191].

S. boulardii treatment limited the infiltration of Th1 cells into the inflamed colon and inhibited proinflammatory cytokine production in mice with IBD [192].

Note that L. crispatus may ameliorate colitis in mice [193]; however, a specific strain, M206119, exacerbated intestinal inflammation [194].

Check individual probiotic posts for more information.

Probiotics may help manage troublesome symptoms in patients with inflammatory bowel disease (IBD). B. longum and S. boulardii produced the best results in human trials, though many strains have only been studied in animals so far.

12) Diverticular Disease

L. paracasei, in association with a high-fiber diet, effectively reduced abdominal bloating and prolonged abdominal pain in patients with symptomatic uncomplicated diverticular disease [195].


Probiotic supplements are a promising avenue for preventing and managing many intestinal conditions from diarrhea and constipation to IBD, damage from antibiotics, and even necrotizing enterocolitis. If you are suffering from persistent digestive symptoms, talk to your doctor about whether and which probiotics are right for you.

Further Reading

We’ve compiled deep dives into each potential benefit of probiotics. Check them out here:

About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.


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