Best Probiotic Strains by Goal: Which Ones Have Trial Data, and for What
Probiotic results belong to specific strains, not to the word on the bottle. Here is which strains have the strongest trial data for antibiotics, regularity, colds and cholesterol, where the evidence is thin, and where well-known strains came up empty.
By Kymata Health Editorial Published Last checked
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NOW Foods Probiotic-10, 25 Billion, 30 Veg Caps
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Label: 1 veg capsule: 25 billion CFU from a 10-strain probiotic blend (Lactobacillus and Bifidobacterium strains).
Best for value: the lowest one-time price of the 7 partner products on this page ($11.16, checked Oct 14, 2026).
Key takeaways
From 11 sources- Effects are strain-specific, and a higher CFU count is not necessarily more effective than a lower one1.
- During antibiotics, Saccharomyces boulardii cut antibiotic-associated diarrhea from 18.7% to 8.5% across 21 trials2; Lactobacillus rhamnosus GG cut it from 22.4% to 12.3%, but separately the drop was significant only in children3.
- For regularity, Bifidobacterium lactis added about 1.5 bowel movements a week in adults with constipation4, and in a later review of 30 trials it had a significant effect on stool frequency while mixtures and L. casei Shirota did not5.
- For colds, a Cochrane review of 23 trials found fewer people had at least one upper respiratory infection with probiotics (risk ratio 0.76), with low-certainty evidence6.
- Well-known strains can fail: in 971 young children with stomach illness, LGG did no better than placebo8, and for IBS symptoms a review of 53 trials could not say which strains work10.
What this article covers
2 evidence profilesThe evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
4 rows- AGrade AAntibiotic-associated diarrheaImproved Risk fell from 18.7% to 8.5% (RR 0.47, 95% CI 0.38–0.57; NNT 10); in children from 20.9% to 8.8%, in adults from 17.4% to 8.2%.Saccharomyces boulardii · Meta-analysis · n=4,780 · 2015 · PMID 26216624
- BGrade BDiarrhea risk during antibiotic treatmentImproved Antibiotic-associated diarrhea fell from 22.4% to 12.3% (RR 0.49; low quality of evidence). Separately, the reduction was significant in children (5 RCTs, n=445) but not in adults (6 RCTs, n=863), except in a subset on H. pylori eradication therapy.Probiotics · Meta-analysis · n=1,308 · 2015 · PMID 26365389
- ∅No effectModerate-to-severe illness and diarrhea duration in children with acute stomach illnessNo effect Moderate-to-severe gastroenteritis within 14 days: 11.8% with LGG vs 12.6% with placebo (RR 0.96). No differences in diarrhea duration (median 49.7 vs 50.9 hours), vomiting, day-care absence or household spread.Probiotics · RCT · n=971 · 2018 · PMID 30462938
- CGrade CTotal and LDL cholesterolImproved Total cholesterol fell by 7.8 mg/dL and LDL by 7.3 mg/dL versus placebo; HDL and triglycerides did not change. Effects were larger with higher starting cholesterol, longer treatment and certain strains, and seemed stronger in studies supported by probiotic companies.Probiotics · Meta-analysis · n=1,624 · 2015 · PMID 26512560
Why the strain is what matters
A probiotic is identified by genus, species, subspecies where relevant, and a strain designation, such as Lacticaseibacillus rhamnosus GG (LGG)1. Some effects are specific to one strain, so ODS says clinical recommendations need to be strain-specific1. A product that lists only "Lactobacillus acidophilus" without a strain code is hard to match to a particular trial.
Dose labels can mislead too. Many supplements contain 1 to 10 billion CFU per dose, some 50 billion or more, but higher counts are not necessarily more effective, and the count should be guaranteed at the end of shelf life rather than at manufacture1. Our CFU guide explains how to read the label.
While taking antibiotics: S. boulardii and LGG
This is the best-studied use. In 21 randomized trials with 4,780 people, the yeast S. boulardii lowered the risk of antibiotic-associated diarrhea from 18.7% to 8.5% (NNT 10), in both children and adults2. In 12 trials with 1,499 people, LGG lowered it from 22.4% to 12.3%, with low-quality evidence overall; analysed separately, the reduction was significant in children but not in adults3. A 2018 network meta-analysis that ranked 10 probiotic options across 51 articles (9,569 participants) put LGG first for both effectiveness and tolerability, and found strain combinations no better than single strains11.
ODS adds that starting within 2 days of the first antibiotic dose works better than starting later, that the benefit was seen in children and adults aged 18 to 64 but not in adults 65 and older, and that there is no evidence multi-strain products work better1. One caution from a mechanistic study in mice and people: after antibiotics, a multi-strain probiotic delayed the return of the gut's own bacteria compared with recovering without it9. More detail is in probiotics with antibiotics.
Regularity: Bifidobacterium lactis has the clearest signal
In a 2014 meta-analysis of 14 trials with 1,182 adults with constipation, probiotics shortened gut transit time by 12.4 hours and added 1.3 bowel movements a week overall4. B. lactis added 1.5 a week, while L. casei Shirota showed no significant effect4.
A 2022 update covered 30 trials in adults with chronic constipation: 57% responded to probiotics versus 44% to control (risk ratio 1.28), and stool frequency rose5. B. lactis had a significant effect, but probiotic mixtures, Bacillus coagulans Unique IS2 and L. casei Shirota did not, and stool consistency did not change overall5. Both reviews flagged high heterogeneity and risk of bias45. For fiber, see psyllium husk side effects and how to take it.
Bloating and IBS symptoms: no clear winning strain
In a review of 53 trials with 5,545 adults with IBS, certain combinations and strains appeared to help global symptoms and abdominal pain, but the authors could not draw definitive conclusions about which ones10. ODS reaches a similar view: probiotics might reduce some IBS symptoms, but better trials are needed to pin down the strain, dose and duration1.
For a non-probiotic option, see peppermint oil for IBS.
Colds: a modest, low-certainty benefit
The 2022 Cochrane review pooled 23 trials with 6,950 children, adults and older people6. Probiotics may reduce the number of people with at least one upper respiratory infection (risk ratio 0.76; 16 studies, 4,798 participants) and may shorten an episode by about 1.22 days, both with low-certainty evidence6. They likely reduced antibiotic prescriptions for these infections (risk ratio 0.58, moderate certainty)6.
Most trials used one or two strains, such as Lactobacillus plantarum HEAL9 or Lactobacillus paracasei 8700:2 or N1115, for more than 3 months, and adverse events were minor, mostly digestive6.
Cholesterol: small drops with specific strains
In 30 placebo-controlled trials with 1,624 people, probiotics lowered total cholesterol by 7.8 mg/dL and LDL by 7.3 mg/dL, with no change in HDL or triglycerides7. Effects were larger with higher starting cholesterol, longer treatment and certain strains, and the associations looked stronger in studies supported by probiotic companies7.
ODS lists L. acidophilus, L. acidophilus with B. lactis, and L. plantarum among the strains linked to lower total and LDL cholesterol, while L. helveticus and Enterococcus faecium were not1.
Where a famous strain came up empty, and who should be careful
In a trial at 10 US pediatric emergency departments, 971 children aged 3 months to 4 years with acute gastroenteritis took LGG or placebo for 5 days8. Moderate-to-severe illness occurred in 11.8% with LGG and 12.6% with placebo, and diarrhea lasted about as long in both groups8. The same strain had helped children on antibiotics3, so a result in one setting does not automatically carry over to another8.
Probiotics are unlikely to harm healthy people, and side effects are usually minor1. Rare bloodstream infections have mostly involved people who were severely ill or immunocompromised, and ODS notes that probiotics given to preterm infants may cause serious infection1.
Matching the strain to the goal
For the full evidence tables, see the probiotics and Saccharomyces boulardii pages. What the trials above support:
What it costs a month: supplements priced at the studied dose, beside their evidence grade, in Evidence per Dollar.
- During antibiotics: S. boulardii (adults and children) or LGG (clearer in children), started within 2 days of the first antibiotic dose123.
- Regularity: Bifidobacterium lactis strains have the most consistent stool-frequency data45.
- Fewer colds: one or two strains, such as L. plantarum HEAL9 or L. paracasei 8700:2, taken for more than 3 months, with low-certainty evidence6.
- Cholesterol: L. acidophilus, L. acidophilus with B. lactis, or L. plantarum, for small LDL changes17.
- IBS symptoms: no strain stands out yet10.
- Severely ill, immunocompromised, or caring for a preterm infant: talk with a clinician first1.
Quick answers
Common questions
4 answersDo more CFU or more strains make a probiotic better?
Not necessarily. ODS says higher CFU counts are not necessarily more effective, and for antibiotic-associated diarrhea there is no evidence that multiple strains work better than one1.
What is the best probiotic to take with antibiotics?
Which probiotic strain helps with constipation?
Keep reading
Full evidence profiles
Every graded study, studied doses, interactions and safetyRelated articles
4 articles- ArticleProbiotic CFU Explained: Why the Strain Name Matters More Than the BillionsWhat does CFU mean on a probiotic, and how many do you need?
- ArticleProbiotics With Antibiotics: Two Strains Have the Data, and Strain Is EverythingShould you take probiotics with antibiotics, and which ones?
- ArticleIgG Food Sensitivity Tests: What a Positive Result Really Means, and the Tests That Can Find a Food ProblemDo IgG food sensitivity tests work?
- Article400 IU of Vitamin E Is Either 268 mg or 180 mg. The "d" or "dl" on the Label DecidesHow many mg is 400 IU of vitamin E, and is natural better than synthetic?
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7 products Paid links · we earn a commission- Quick pickHerbsProNOW Foods Probiotic-10, 25 Billion, 30 Veg Caps
1 veg capsule: 25 billion CFU from a 10-strain probiotic blend (Lactobacillus and Bifidobacterium strains)
$11.16one-timeChecked Oct 14, 2026 - SupersmartL. Rhamnosus GG5% off with the Supersmart newsletterGet 5% off with the newsletter (paid link, opens in new tab)
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2 capsules: 10 billion CFU Lactobacillus rhamnosus GG (LifeinU) + 250 mg inulin; 30 servings
$21.00one-time$17.85subscribeChecked Oct 11, 2026 - OnnitOnnit Total GUT HEALTH (60 capsules)We use this brand at home. What we use
DGrade D, preliminary (Grade D) No trial of this formula; probiotic effects are specific to the strain and the dose.
4 capsules: 10 billion CFU probiotic blend (7 strains) and 5 billion CFU Saccharomyces boulardii, with digestive enzymes, betaine HCl and a prebiotic herbal blend; 15 servings
$23.99one-timeChecked Oct 20, 2026 - Physician’s ChoicePhysician’s Choice 60 Billion Probiotic (30 capsules)
1 capsule: 60 billion CFU at expiration from a 10-strain blend of lactobacilli and bifidobacteria (220 mg), plus a 150 mg organic inulin and acacia fiber prebiotic blend; 30 servings
$29.38one-timeChecked Oct 20, 2026 - Dr. TobiasDr. Tobias Probiotics 30 Billion (30 capsules)
1 capsule: 30 billion CFU including Lactobacillus acidophilus, Bacillus subtilis DE111 and Bacillus coagulans
$26.99one-timeChecked Oct 14, 2026 - GoliGoli Probiotic+ Gummies, 60 gummies
3 gummies: 10 mg Bacillus subtilis DE111, 20 mg postbiotic MCC1849 (heat-stable Lactobacillus paracasei) and 50 mg xylooligosaccharides; amounts are listed in mg, not CFU; label suggests 3 gummies once daily
$15.98one-timeChecked Oct 15, 2026 - Physician’s ChoicePhysician’s Choice Women’s Probiotic (30 capsules)
1 capsule: 50 billion CFU from a 6-strain blend (133 mg) of L. plantarum, L. paracasei, L. casei, L. gasseri, L. acidophilus and B. lactis, plus 100 mg organic inulin and acacia fiber, 60 mg D-mannose and 50 mg cranberry fruit powder; the label lists species without strain codes; 30 servings
$27.92one-timeChecked Oct 20, 2026
References
11 sources. Numbers in the text link here.
Sources cited in this article
11 sources- 1Probiotics: Fact Sheet for Health Professionals (Updated March 25, 2025)NIH Office of Dietary Supplements, 2025
- 2Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoeaAliment Pharmacol Ther, 2015 · PMID 26216624
- 3Systematic review with meta-analysis: Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adultsAliment Pharmacol Ther, 2015 · PMID 26365389
- 4The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trialsAm J Clin Nutr, 2014 · PMID 25099542
- 5Probiotics and synbiotics in chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trialsClin Nutr, 2022 · PMID 36372047
- 6Probiotics for preventing acute upper respiratory tract infectionsCochrane Database Syst Rev, 2022 · PMID 36001877
- 7Effect of Probiotics on Blood Lipid Concentrations: A Meta-Analysis of Randomized Controlled TrialsMedicine (Baltimore), 2015 · PMID 26512560
- 8Lactobacillus rhamnosus GG versus Placebo for Acute Gastroenteritis in ChildrenN Engl J Med, 2018 · PMID 30462938
- 9Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMTCell, 2018 · PMID 30193113
- 10Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndromeAliment Pharmacol Ther, 2018 · PMID 30294792
- 11Comparative efficacy and tolerability of probiotics for antibiotic-associated diarrhea: Systematic review with network meta-analysisUnited European Gastroenterol J, 2018 · PMID 29511547
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