Home Ingredients Lactobacillus acidophilus LA-5™ (DSM 13241)

Lactobacillus acidophilus LA-5™ (DSM 13241)

Lactobacillus acidophilus
Evidence Level
Limited
2 Clinical Trials
5 Documented Benefits
2/5 Evidence Score

LA-5 is a single strain of the probiotic species Lactobacillus acidophilus, deposited as DSM 13241 and isolated from the dairy culture collection of Chr. Hansen, now part of Novonesis. It is distinct from the NCFM and DDS-1 strains of the same species and is most often sold paired with Bifidobacterium animalis subsp. lactis BB-12, in capsules or in probiotic yogurts. In a placebo-controlled trial in 234 women after childbirth, 2 billion CFU a day for 8 weeks was followed by fewer positive urine cultures at a scheduled 8 week check, a count that included infections without symptoms, with better quality of life scores. In women with vaginal yeast overgrowth, LA-5 alone did not match a single fluconazole dose, and that trial had no placebo group. Most other human trials tested LA-5 with BB-12 or other strains, so their bowel and antibiotic-period results belong to those blends, and several were null.

Studied Dose LA-5 alone: 2 billion CFU once daily for 8 weeks (women after childbirth); 30 daily capsules at 1 billion CFU per gram (vaginal yeast trial). Blends: about 8.3 billion CFU of La-5 a day in a three-strain yogurt; other blend doses vary. The maker gives no dose.
Active Compound Live Lactobacillus acidophilus strain LA-5 (DSM 13241), freeze-dried. The maker states the strain was isolated from Chr. Hansen's collection of dairy cultures and that LA-5 is a trademark of Chr. Hansen A/S, part of Novonesis Group, offered in multiple formats. It is commonly combined with B. animalis subsp. lactis BB-12, for example as Probio-Tec AB-25 in a colitis trial, and is added to probiotic yogurts with other strains.

Benefits

Urinary tract health in women after childbirth

In a placebo-controlled trial in 234 women after giving birth, LA-5 alone at 2 billion CFU a day for 8 weeks was followed by fewer positive urine cultures at a scheduled 8 week check, the primary outcome, which counted infections with or without symptoms (adjusted odds ratio 0.41, p = 0.033). Case numbers and an unadjusted result were not reported in the summary. It is a single, university-funded trial.

Supported by Trial 1

Quality of life scores in women

In the same trial in women after childbirth, overall quality of life and its mental health domain scored better on LA-5 than placebo, as secondary outcomes. A separate 8 week trial in 64 women found better sexual function and menopause quality of life scores on L. acidophilus from the same supplier, but that paper did not name the strain.

Supported by Trial 1

Vaginal yeast balance compared with a standard antifungal

In 80 women with vaginal yeast overgrowth, 30 days of LA-5 alone was compared with one fluconazole dose, with no placebo group. Negative cultures were similar at about 1 month but less frequent on LA-5 at 2 months, and discharge, redness and itching were lower after fluconazole. LA-5 is not a substitute for antifungal treatment.

Supported by Trial 2

Bowel symptoms with the LA-5 and BB-12 blend

In 200 adults with IBS without constipation, an LA-5 and BB-12 blend for 84 days gave more global responders than placebo (19.3% versus 8.9% at day 28) and lower symptom scores. A 6 month trial of La5, Bb12 and L. paracasei F19 in 131 adults with IBS found no difference from placebo. These are blends, not LA-5 alone.

Supported by Trial 1, Trial 2

Stool consistency during antibiotic courses (LA-5 blends)

In 70 children on antibiotics, a yogurt with La-5, BB-12 and L. rhamnosus GG was followed by fewer loose stool episodes than a pasteurized yogurt. In adults, an LA-5 and BB-12 product and a three-strain yogurt in 314 older inpatients did not lower diarrhea incidence versus placebo. Results belong to these blends taken alongside antibiotics.

Supported by Trial 2, Trial 1

Mechanism of action

1

Secreted molecules and E. coli O157:H7 (lab and mouse work)

Molecules that La-5 releases into its growth medium reduced the attachment of E. coli O157:H7 to cultured human cells and the lesions it forms there, and in mice given these fractions by mouth, gut colonization and fecal shedding of the labeled bacteria fell. This has not been tested in people.

2

C. difficile toxins in cell culture (lab work)

In human colon cell lines, the cell-free supernatant of La-5 cultures reduced damage from C. difficile toxins and reduced attachment of C. difficile cells, including when the cells were treated beforehand. These are laboratory findings only.

Clinical trials

1
LA-5 vs Placebo for 8 Weeks in Women After Childbirth: Urinary Tract Outcome
PubMed

Double-blind, randomized, placebo-controlled trial in Tabriz, Iran (IRCT20120718010324N81); a 500 mg capsule of L. acidophilus La5 at 2 billion CFU or a corn starch placebo once daily for 8 weeks; primary outcome urinary infection on a scheduled urine culture at 8 weeks, defined in the registry as cystitis, pyelonephritis or asymptomatic bacteriuria; the registry lists the product as L. acidophilus from the Iranian representative of Chr. Hansen; secondary outcomes quality of life, breastfeeding performance, infant growth and adverse effects; funded by Tabriz University of Medical Sciences, with no company authors and no competing interests declared (Borhani et al. 2026, Probiotics Antimicrob Proteins)

234 women in the weeks after giving birth.

Urinary infection on culture, the primary outcome, was less frequent on La5 than on placebo (adjusted odds ratio 0.41, 95% CI 0.17 to 0.93, p = 0.033); the abstract gives no case numbers, no unadjusted result and no split between infections with and without symptoms. Overall quality of life (p = 0.003) and its mental health domain (p = 0.004) favored La5. Breastfeeding performance (p = 0.335) and infant growth (p = 0.493) did not differ. This is the only placebo-controlled trial of LA-5 alone found.

2
LA-5 vs a Single Fluconazole Dose in Vaginal Yeast Overgrowth (No Placebo Group)
PubMed

Triple-blinded, randomized, double-dummy trial in Tabriz, Iran (IRCT20110826007418N5); 30 once-daily capsules of L. acidophilus LA-5 (1 billion CFU per gram, ordered from Chr. Hansen) plus a dummy fluconazole capsule, or a single 150 mg fluconazole dose plus 30 dummy probiotic capsules; cultures, vaginal pH and symptoms at 30 to 35 and 60 to 65 days; the comparator was a drug, not a placebo; the authors declared no competing interests (Mollazadeh-Narestan et al. 2023, Probiotics Antimicrob Proteins)

80 married women aged 18 to 49 with clinically and laboratory confirmed vulvovaginal candidiasis.

Negative cultures did not differ at 30 to 35 days (p = 0.127) but were more frequent after fluconazole at 60 to 65 days (p = 0.016). Discharge and redness at both visits, and itching at the second, were lower after fluconazole; burning, urinary frequency, painful urination and painful intercourse did not differ. Each arm had two reported side effects (on LA-5, one nausea and one flatulence), and before the second visit two women left the LA-5 arm citing nausea and one citing stomach problems. With no placebo arm, the trial cannot show an effect of LA-5 itself.

Side effects and drug interactions

Common Potential side effects

In the trial of LA-5 alone in vaginal yeast overgrowth, one woman reported nausea and one flatulence on LA-5, the same number of side effects as on fluconazole, but two women left the LA-5 group because of nausea and one because of stomach problems. In an Indian trial, an LA-5 and BB-12 product had four mild adverse events (2.0%) versus none on placebo, and in an IBS trial of the blend, mild or moderate events did not differ significantly from placebo.
Lactobacilli, including L. acidophilus, have rarely caused bloodstream and heart valve infections, mostly in immunocompromised or diabetic people; people who are severely immunocompromised or critically ill should check with a doctor before using live probiotics.
The single-strain trials lasted 8 weeks or about 1 month, so longer-term data on LA-5 alone are lacking.

Important Drug interactions

Antibiotics: in the blend trials, the probiotic was taken during the antibiotic course. Antibiotics can kill live bacteria, so ask your pharmacist about spacing a probiotic from antibiotic doses.
Antifungals: in the vaginal yeast trial, LA-5 alone did less well than one 150 mg fluconazole dose on cultures at 2 months; do not use LA-5 in place of prescribed antifungal treatment.
Immunosuppressants and chemotherapy: people taking drugs that weaken the immune system should use live probiotics only with medical advice.
No drug interaction studies of LA-5 were found among the cited sources. Tell your doctor or pharmacist about any supplement you take.

Frequently asked questions about Lactobacillus acidophilus LA-5™ (DSM 13241)

What is LA-5 and how is it different from other acidophilus strains?

LA-5 is one strain of Lactobacillus acidophilus, deposited as DSM 13241 and supplied by Chr. Hansen, now part of Novonesis. NCFM and DDS-1 are other strains of the same species with their own trials. Results are strain specific, so check that the label names LA-5 if that is the strain you want.

Is LA-5 usually sold alone or with BB-12?

It is most often combined with B. animalis subsp. lactis BB-12, in capsules and in probiotic yogurts, sometimes with other strains. Most human trials tested such blends, and the share of LA-5 in each is often not stated. Only two trials found tested LA-5 alone, one against placebo and one against an antifungal drug.

How much LA-5 was used in studies?

The placebo-controlled trial of LA-5 alone used 2 billion CFU once a day for 8 weeks. A trial against fluconazole used 30 daily capsules at 1 billion CFU per gram. Blend products used other amounts, such as about 8 billion CFU of La-5 a day in a children's yogurt. The maker gives no dose; follow the product label.

Is LA-5 safe?

In the trials cited here, side effects such as nausea or gas were few, and rates were similar to the comparison groups. As with all lactobacilli, rare bloodstream infections have been reported, mostly in people with weakened immunity, so people who are severely ill or immunocompromised should ask a doctor first.

What is Lactobacillus acidophilus LA-5?

LA-5 is a single strain of the probiotic species Lactobacillus acidophilus, deposited as DSM 13241 and isolated from the dairy culture collection of Chr. Hansen, now part of Novonesis. It is distinct from the NCFM and DDS-1 strains of the same species and is most often sold paired with Bifidobacterium animalis subsp.

What is Lactobacillus acidophilus LA-5 used for?

NutraSmarts does not list Lactobacillus acidophilus LA-5 under a health category. What the research covers: In a placebo-controlled trial in 234 women after giving birth, LA-5 alone at 2 billion CFU a day for 8 weeks was followed by fewer positive urine cultures at a scheduled 8 week check, the primary outcome, which counted infections with or wi…

Does Lactobacillus acidophilus LA-5 interact with any medications?

Possible interactions include: Antibiotics: in the blend trials, the probiotic was taken during the antibiotic course. Antibiotics can kill live bacteria, so ask your pharmacist about spacing a probiotic from antibiotic doses. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Lactobacillus acidophilus LA-5?

NutraSmarts rates the evidence for Lactobacillus acidophilus LA-5 as Limited (2 out of 5). It is backed by 2 study summaries and 13 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(13 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Borhani F, Abbasalizadeh F, Mohammad-Alizadeh-Charandabi S, Homayouni-Rad A, Mirghafourvand M. The Effect of Lactobacillus Acidophilus (La5) on the Incidence of Urinary Tract Infection in the Puerperium: A Randomized Placebo-Controlled Trial. Probiotics Antimicrob Proteins. 2026;18(2):2746-2758. doi: 10.1007/s12602-025-10719-8.PubMedUsed to support: Double-blind, randomized, placebo-controlled trial in Tabriz, Iran, in 234 women after childbirth: a 500 mg capsule of L. acidophilus La5 at 2 billion CFU once daily for 8 weeks, or a corn starch placebo. Urinary infection on a scheduled urine culture at 8 weeks, the primary outcome (defined in the registry as cystitis, pyelonephritis or asymptomatic bacteriuria), was less frequent on the probiotic (adjusted odds ratio 0.41, 95% CI 0.17 to 0.93, p = 0.033); the abstract reports no case numbers or unadjusted result. Overall quality of life and its mental health domain also favored the probiotic; breastfeeding performance and infant growth did not differ. Funded by Tabriz University of Medical Sciences; the authors declared no competing interests. Registered IRCT20120718010324N81.
  2. Mollazadeh-Narestan Z, Yavarikia P, Homayouni-Rad A, Samadi Kafil H, Mohammad-Alizadeh-Charandabi S, Gholizadeh P, Mirghafourvand M. Comparing the Effect of Probiotic and Fluconazole on Treatment and Recurrence of Vulvovaginal Candidiasis: a Triple-Blinded Randomized Controlled Trial. Probiotics Antimicrob Proteins. 2023;15(5):1436-1446. doi: 10.1007/s12602-022-09997-3.PubMedUsed to support: Triple-blinded randomized trial in 80 women with confirmed vulvovaginal candidiasis comparing 30 daily capsules of L. acidophilus LA-5 (1 billion CFU per gram, ordered from Chr. Hansen) plus a dummy fluconazole capsule with a single 150 mg fluconazole dose plus dummy probiotic capsules. There was no placebo group. Negative cultures did not differ at 30 to 35 days (p = 0.127) but were more frequent on fluconazole at 60 to 65 days (p = 0.016), and discharge, redness and later itching were lower on fluconazole; burning, urinary frequency, painful urination and painful intercourse did not differ. Registered IRCT20110826007418N5; the authors declared no competing interests.
  3. Valizadeh R, Borhani F, Shabani F, Mirghafourvand M. The effect of probiotic supplementation on sexual function in premenopausal and menopausal women: a randomized controlled clinical trial. Sci Rep. 2025;16(1):1254. doi: 10.1038/s41598-025-30879-5.PubMedUsed to support: Double-blind, randomized trial in 64 premenopausal and menopausal women with sexual dysfunction in Tabriz, Iran: a 250 mg capsule of L. acidophilus at 3 billion CFU once daily for 8 weeks, or a corn starch placebo. The total Female Sexual Function Index, the primary outcome, was higher on the probiotic (median 19.1 versus 18.2, p = 0.038) and the menopause quality of life score was lower, meaning better (25.1 versus 30.9, p < 0.001). The paper does not name the strain; it states only that the L. acidophilus was obtained from Chr. Hansen's representative in Iran, so the result is not counted here as an LA-5 result. Funded by Tabriz University of Medical Sciences.
  4. Ghoshal UC, Ramakrishna BS, Rathi PM, Shukla A, Panigrahi MK, Jain S, Saha I, Chakravartty K, Singh M, Mustafa U, Sahu S, Ghoshal U, Chandnani S, Goenka MK, Mitra M. Probiotic Blend of Lactobacillus acidophilus LA-5 and Bifidobacterium animalis ssp. Lactis BB-12 in Non-constipated Irritable Bowel Syndrome: A Double-Blind Randomized Placebo-Controlled Trial. J Gastroenterol Hepatol. 2026;41(1):140-154. doi: 10.1111/jgh.70137.PubMedUsed to support: Blend, not LA-5 alone. Double-blind, randomized, placebo-controlled trial in 200 adults in India with IBS without constipation: a combination of LA-5 and BB-12, or placebo, for 84 days. Response on the IBS Global Improvement Scale was higher on the blend at day 28 (19.3% versus 8.9%, p = 0.048) and at days 56 and 84, and symptom severity and quality of life scores fell more; fecal microbiota did not differ between groups. Mild or moderate adverse events were 4.0% versus 0.9% (p = 0.167). The abstract does not give the dose, the share of each strain or the funding source.
  5. Fox MJ, Ahuja KD, Robertson IK, Ball MJ, Eri RD. Can probiotic yogurt prevent diarrhoea in children on antibiotics? A double-blind, randomised, placebo-controlled study. BMJ Open. 2015;5(1):e006474. doi: 10.1136/bmjopen-2014-006474.PubMedUsed to support: Blend, given alongside antibiotics. Double-blind, randomized trial in 72 children aged 1 to 12 starting antibiotics (70 completed): 200 g a day of a supermarket probiotic yogurt with L. rhamnosus GG (mean 5.2 billion CFU a day), BB-12 (5.9 billion) and La-5 (8.3 billion), or a pasteurized yogurt, for the antibiotic course. Severe loose stool episodes were 0 versus 6 (p = 0.025) and minor episodes 1 versus 21 (p < 0.001). La-5 was about 43% of the probiotic count, so the result belongs to the three-strain yogurt. Supported by Parmalat Australia, which supplied the yogurts. Registered ACTRN12609000281291.
  6. Velasco M, Requena T, Delgado-Iribarren A, Peláez C, Guijarro C. Probiotic Yogurt for the Prevention of Antibiotic-associated Diarrhea in Adults: A Randomized Double-blind Placebo-controlled Trial. J Clin Gastroenterol. 2019;53(10):717-723. doi: 10.1097/MCG.0000000000001131.PubMedUsed to support: Blend, given alongside antibiotics. Randomized, double-blind trial in 314 hospitalized adults (mean age 76) starting antibiotics: 200 mL a day of yogurt with La-5, BB-12 and L. casei Lc-01, a plain yogurt placebo, or no yogurt. Diarrhea occurred in 23.0% on the probiotic yogurt versus 17.6% on placebo (p = 0.30), and its duration and severity did not differ.
  7. Chatterjee S, Kar P, Das T, Ray S, Gangulyt S, Rajendiran C, Mitra M. Randomised placebo-controlled double blind multicentric trial on efficacy and safety of Lactobacillus acidophilus LA-5 and Bifidobacterium BB-12 for prevention of antibiotic-associated diarrhoea. J Assoc Physicians India. 2013;61(10):708-12..PubMedUsed to support: Blend, given alongside antibiotics. Double-blind, randomized, placebo-controlled multicenter trial in adults on a 7 day course of cefadroxil or amoxicillin: an LA-5 and BB-12 formulation for 14 days. Antibiotic-associated diarrhea was 10.8% versus 15.6% on placebo (p = 0.19, not significant); diarrhea that did occur lasted a median 2 versus 4 days (p = 0.01). Four mild adverse events (2.0%) occurred on the probiotic and none on placebo.
  8. Wildt S, Nordgaard I, Hansen U, Brockmann E, Rumessen JJ. A randomised double-blind placebo-controlled trial with Lactobacillus acidophilus La-5 and Bifidobacterium animalis subsp. lactis BB-12 for maintenance of remission in ulcerative colitis. J Crohns Colitis. 2011;5(2):115-21. doi: 10.1016/j.crohns.2010.11.004.PubMedUsed to support: Blend, not LA-5 alone. Double-blind, randomized (2:1), placebo-controlled trial in 32 adults with left-sided ulcerative colitis in remission: Probio-Tec AB-25 (La-5 plus BB-12) or placebo for 52 weeks. Remission was maintained in 25% versus 8% (p = 0.37) and time to relapse did not differ (p = 0.683); the product was well tolerated. One author (Brockmann E) was affiliated with Chr. Hansen A/S, the maker. Registered NCT00268164.
  9. Begtrup LM, de Muckadell OB, Kjeldsen J, Christensen RD, Jarbøl DE. Long-term treatment with probiotics in primary care patients with irritable bowel syndrome--a randomised, double-blind, placebo controlled trial. Scand J Gastroenterol. 2013;48(10):1127-35. doi: 10.3109/00365521.2013.825314.PubMedUsed to support: Blend, not LA-5 alone. Randomized, double-blind, placebo-controlled trial in 131 primary care adults with IBS (Rome III): two capsules twice daily of L. paracasei F19, L. acidophilus La5 and Bifidobacterium Bb12 (1.3 x 10^10 CFU per capsule) for 6 months. Responders on adequate relief, the primary outcome, were 52% versus 41% on placebo (p = 0.18), and symptoms and quality of life did not differ between groups.
  10. Medellin-Peña MJ, Griffiths MW. Effect of molecules secreted by Lactobacillus acidophilus strain La-5 on Escherichia coli O157:H7 colonization. Appl Environ Microbiol. 2009;75(4):1165-72. doi: 10.1128/AEM.01651-08.PubMedUsed to support: Lab and mouse study. Cell-free fractions of La-5 spent culture medium reduced attaching and effacing lesions and adhesion of E. coli O157:H7 on cultured human cells, and in mice given the fraction by gavage, gut bioluminescence from labeled E. coli and fecal shedding fell. Not a human study.
  11. Najarian A, Sharif S, Griffiths MW. Evaluation of protective effect of Lactobacillus acidophilus La-5 on toxicity and colonization of Clostridium difficile in human epithelial cells in vitro. Anaerobe. 2019;55:142-151. doi: 10.1016/j.anaerobe.2018.12.004.PubMedUsed to support: Lab study. La-5 cell-free supernatant reduced the toxicity of C. difficile culture filtrate to HT-29 and Caco-2 human colon cell lines and reduced attachment of C. difficile cells, including when the cells were pretreated. Not a human study.
  12. Rossi F, Amadoro C, Gasperi M, Colavita G. Lactobacilli Infection Case Reports in the Last Three Years and Safety Implications. Nutrients. 2022;14(6):1178. doi: 10.3390/nu14061178.PubMedUsed to support: Review of lactobacilli infection case reports from 2019 to 2021 (17, 15 and 16 cases a year), including endocarditis and bacteremia, mostly in diabetic and immunocompromised people with risk factors; L. acidophilus accounted for 5 cases. Not specific to LA-5.
  13. Novonesis (Chr. Hansen A/S). L. acidophilus, LA-5™ (product page) Novonesis website. 2026;Manufacturer product page; accessed 2026-11-07..SourceUsed to support: Not PubMed-indexed (manufacturer web page). States that L. acidophilus LA-5™ (DSM 13241) was isolated from Chr. Hansen's collection of dairy cultures, that LA-5 is a trademark of Chr. Hansen A/S, part of Novonesis Group, and that it is offered in multiple formats; it presents some uses for LA-5 alone and gut uses for the combination with BB-12. The page gives no dose. The maker's own claims on this page are not evidence and are not repeated here.