Lactobacillus acidophilus
Research reviewed: Up until 03/2026
Lactobacillus acidophilus is a dietary supplement with 8 published peer-reviewed studies involving 903 participants, researched for Gut Health & IBS, Diarrhea Prevention, Immune Support.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Gut Health & IBS
StrongDiarrhea Prevention
StrongImmune Support
StrongResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Gut Health & IBS
To evaluate the efficacy of L. acidophilus in reducing IBS symptoms.
Study Type
Double-blind, placebo-controlled RCT
Purpose
To evaluate the efficacy of L. acidophilus in reducing IBS symptoms.
Dose
10 billion CFU/day
Participants
60 patients with IBS
Duration
8 weeks
Results
L. acidophilus significantly reduced abdominal pain and bloating scores compared to placebo. Overall IBS-SSS improved by 42% in the treatment group.
How They Measured It
IBS Severity Scoring System (IBS-SSS)
To assess efficacy of L. acidophilus NCFM on visceral pain sensitivity in IBS-D patients.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess efficacy of L. acidophilus NCFM on visceral pain sensitivity in IBS-D patients.
Dose
2 × 10^10 CFU/day L. acidophilus NCFM
Participants
74 IBS-D patients
Duration
4 weeks
Results
L. acidophilus NCFM induced expression of mu-opioid and cannabinoid receptors in intestinal epithelial cells, leading to significant increase in pain thresholds.
How They Measured It
Rectal distension pain thresholds, symptom diaries
To evaluate the overall efficacy of L. acidophilus strains in IBS treatment.
Study Type
Meta-analysis
Purpose
To evaluate the overall efficacy of L. acidophilus strains in IBS treatment.
Dose
Various (1-20 billion CFU/day)
Participants
Meta-analysis of 5 RCTs, 419 patients
Duration
4-12 weeks
Results
L. acidophilus demonstrated modest but significant improvement in overall IBS symptoms compared to placebo, with strongest effects on bloating and abdominal pain.
How They Measured It
Pooled analysis of symptom improvement across RCTs
Diarrhea Prevention
To determine whether L. acidophilus prevents antibiotic-associated diarrhea (AAD).
Study Type
Randomised controlled trial
Purpose
To determine whether L. acidophilus prevents antibiotic-associated diarrhea (AAD).
Dose
2 billion CFU/day
Participants
202 hospitalized patients on antibiotics
Duration
Duration of antibiotic course + 1 week
Results
L. acidophilus group had significantly lower incidence of AAD (12% vs 34% placebo). Duration of diarrhea episodes was also reduced.
How They Measured It
Incidence and duration of diarrhea episodes
To evaluate probiotics including L. acidophilus for prevention of travelers' diarrhea.
Study Type
Meta-analysis
Purpose
To evaluate probiotics including L. acidophilus for prevention of travelers' diarrhea.
Dose
Various L. acidophilus strains
Participants
Meta-analysis of 12 RCTs, 4709 travelers
Duration
1-3 weeks travel duration
Results
L. acidophilus-containing probiotics showed a significant reduction in travelers' diarrhea risk (RR 0.85, 95% CI 0.79-0.91).
How They Measured It
Pooled risk ratios from included RCTs
To assess L. acidophilus in prevention of Clostridium difficile-associated diarrhea.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess L. acidophilus in prevention of Clostridium difficile-associated diarrhea.
Dose
10 billion CFU/day
Participants
138 hospitalized elderly patients
Duration
20 days
Results
Incidence of C. difficile toxin-positive diarrhea was significantly lower in the L. acidophilus group (2.9% vs 7.3% placebo).
How They Measured It
Incidence of C. difficile toxin-positive diarrhea
Immune Support
To evaluate the immunomodulatory effects of L. acidophilus supplementation.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate the immunomodulatory effects of L. acidophilus supplementation.
Dose
5 billion CFU/day
Participants
326 healthy adults
Duration
6 months
Results
L. acidophilus supplementation significantly increased NK cell activity and reduced the incidence and duration of respiratory infections by 34% compared to placebo.
How They Measured It
NK cell activity, cytokine levels, incidence of respiratory infections
To evaluate the effect of L. acidophilus on immune response to influenza vaccination in elderly.
Study Type
Randomised controlled trial
Purpose
To evaluate the effect of L. acidophilus on immune response to influenza vaccination in elderly.
Dose
10 billion CFU/day
Participants
86 elderly nursing home residents
Duration
13 weeks
Results
L. acidophilus group showed significantly higher seroconversion rates and antibody titers to influenza vaccine compared to placebo.
How They Measured It
Seroconversion rates, antibody titers
Frequently Asked Questions
Common questions about Lactobacillus acidophilus research
There are currently 8 peer-reviewed studies on Lactobacillus acidophilus (Lactobacillus acidophilus), involving 903 total participants. Research covers Gut health, IBS symptom relief, Immune support and 1 more areas. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (6 human studies), and reported outcomes.
Lactobacillus acidophilus has been researched for: Gut health, IBS symptom relief, Immune support, Diarrhea prevention. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 6 out of 8 studies are human trials. Human trials carry more weight in our evidence scoring system.
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