Lactobacillus acidophilus is a species of bacteria that’s considered beneficial to our health. It often resides in the microbiomes of the gut, skin and vagina.
It also lives in many types of fermented foods, and it’s added to some probiotic products. This type of bacteria was first named in 1900, and you’ll see it written as L. acidophilus.
Below, we’ll investigate the potential health benefits of L. acidophilus and explain the latest research. We’ll also cover any risks associated with taking L. acidophilus probiotics.
L. acidophilus and health
Because scientists have known about L. acidophilus for more than a century, a fair amount of research has explored its health effects.
Below, we’ll cover research into this bacteria’s effects on vaginal health, eczema, irritable bowel syndrome (IBS) and more.
But we’ll begin by looking at L. acidophilus and symptoms associated with taking antibiotics, because this topic has the most evidence so far.
Antibiotic-associated gut symptoms
Nausea, diarrhoea and other gut symptoms are common side effects of antibiotics.
For some people, these symptoms are so unpleasant that they stop taking the antibiotic before the treatment is complete. This prevents the medication from getting rid of the infection.
Also, stopping a course of antibiotics early increases the risk of developing antibiotic-resistant bacteria.
So, to help reduce the side effects of antibiotics, doctors sometimes recommend eating yoghurt that contains L. acidophilus.
In 1995, a study confirmed that taking this bacteria orally during a course of antibiotics was associated with fewer unpleasant gut symptoms.
Fifteen years later, a review and meta-analysis of 10 studies confirmed this finding. The authors determined that taking Lactobacillus reduced antibiotic-associated diarrhoea for adults, though they didn’t find the same benefits for children.
A Cochrane review – the gold-standard of evidence-based reviews – concluded that there’s ‘moderate-quality evidence’ that probiotic therapy, including treatment with L. acidophilus, can reduce the risk of antibiotic-associated diarrhoea.
Protection against Helicobacter pylori infection
H. pylori is a common stomach infection. Usually it doesn’t cause symptoms, but it can lead to stomach ulcers in some people.
There’s some evidence that oral L. acidophilus supplements may help tackle H. pylori infections.
Probiotics alone can’t treat H. pylori. But when L. acidophilus supplements are paired with a standard antibiotic treatment, they seem to both improve the treatment and reduce any side effects of the antibiotics.
Vaginal health
As we mentioned earlier, L. acidophilus is often a member of the vaginal microbiome.
Evidence suggests that its presence is associated with a reduced risk of microbiome-related vaginal conditions, such as bacterial vaginosis and aerobic vaginitis.
Taking L. acidophilus orally or as a suppository (inserted into the vagina with an applicator) seems to be effective treatment for some people.
IBS
IBS is a common condition that affects the digestive system. Symptoms often include stomach cramps, bloating, constipation and diarrhoea.
Some research suggests that L. acidophilus supplements can reduce abdominal pain and improve both bowel habits and the quality of life for people with IBS.
Many studies investigating probiotics and IBS test a cocktail of bacterial strains. This approach can make it challenging to tease apart the specific effects of different strains.
However, according to the authors of one review, every study that reported improved IBS symptoms had included L. acidophilus in the mix.
Eczema
There’s some evidence that taking a probiotic containing L. acidophilus during pregnancy might prevent eczema for the infant.
There’s less evidence in adults. However, the authors of one review suggest that taking L. acidophilus alongside standard eczema treatment might help relieve symptoms by reducing inflammation.
Lactose intolerance
Lactose intolerance means that it’s difficult to digest lactose, the sugar in milk and other dairy products.
Symptoms generally include excess wind, diarrhoea, bloating, stomach cramps and, occasionally, nausea or vomiting. The studies we cover next suggest that L. acidophilus supplementation might help treat this condition.
For instance, one study determined that supplements containing L. acidophilus and Bifidobacterium decreased symptoms of lactose intolerance.
Another study found that taking a supplement containing a strain of L. acidophilus every day for 4 weeks reduced diarrhoea, abdominal cramping, vomiting and overall symptoms associated with lactose intolerance.
A 2020 review also concluded that L. acidophilus specifically can help manage symptoms of lactose intolerance.
To learn more about managing lactose intolerance, have a look at this article.
Other conditions
Scientists have investigated whether L. acidophilus might help relieve a wide range of other conditions.
Although the evidence isn’t compelling, some research suggests that this species of bacteria might help lower cholesterol levels, reduce inflammation, prevent certain types of cancer, manage allergies and reduce infection risk.
Overall, it’s clear that research into this fascinating microbe is likely to continue long into the future.
Side effects, safety and interactions
Experts agree that L. acidophilus is safe. For most people, it doesn’t cause any issues.
Rarely, some people might experience minor side effects, like excess wind and bloating. These tend to be short-lived and improve on their own.
If you have a chronic health condition, including a severely compromised immune system, or if you have any other concerns, check with a healthcare professional before you take L. acidophilus.
FAQs
Now we’ll cover some frequently asked questions about this type of bacteria.
Who shouldn’t take L. acidophilus?
Unless you’re very ill or have a compromised immune system, experts consider L. acidophilus supplements to be safe.
What’s the most common disease caused by this bacteria?
Scientists don’t consider L. acidophilus to be a disease-causing bacteria.
Does L. acidophilus cause weight gain?
Weight management is complex, in part because so many factors contribute to increases and decreases. Beyond diet and physical activity, stress, sleep, medications and health conditions can all play a role.
Although it's early days, some scientists think that the gut microbiome influences weight management, too.
That’s why researchers are exploring gut microbiome-targeted therapies, including probiotics, for weight management.
There hasn’t been a lot of research with humans so far, but the general consensus is that probiotics, including L. acidophilus, are likely to support, rather than hinder, weight loss.
Where is L. acidophilus found?
L. acidophilus naturally occurs in the microbiomes of the gut, mouth and vagina. It’s also present in some fermented foods and probiotic supplements.
Summary
L. acidophilus supplementation may have some health benefits, including:
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relieving antibiotic-associated gut symptoms
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protecting against H. pylori infections
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reducing the risk of bacterial vaginosis and aerobic vaginitis
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improving symptoms of IBS
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relieving eczema symptoms in children
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improving lactose intolerance
This list may steadily grow as scientists continue to explore this bacteria’s effects on our health. Importantly, L. acidophilus is safe and well-tolerated by most people.
To learn more about other gut health topics, visit Symprove’s Gut Hub.
Sources
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Clustering analysis of the multi-microbial consortium by Lactobacillus species against vaginal dysbiosis among Ecuadorian women. Frontiers in Cellular and Infection Microbiology. (2022). Link.
Comparative meta-analysis of the effect of Lactobacillus species on weight gain in humans and animals. Microbial Pathogenesis. (2012). Link.
Effect of Lactobacillus acidophilus on antibiotic-associated gastrointestinal morbidity: A prospective randomized trial. Journal of Otolaryngology. (1995). Link.
Effect of Lactobacillus on body weight and body fat in overweight subjects: A systematic review of randomized controlled clinical trials. International Journal of Obesity. (2017). Link.
Effect of probiotic mix (Bifidobacterium bifidum, Bifidobacterium lactis, Lactobacillus acidophilus) in the primary prevention of eczema: A double-blind, randomized, placebo-controlled trial. Pediatric Allergy and Immunology. (2010). Link.
Effects of probiotics administration on lactose intolerance in adulthood: A meta-analysis. Journal of Dairy Science. (2023). Link.
Effects of probiotics on the recurrence of bacterial vaginosis: A review. Journal of Lower Genital Tract Disease. (2014). Link.
Examining the efficacy of five Lactobacillus species in treating and preventing atopic dermatitis: A systemic literature review. Cureus. (2024). Link.
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Helicobacter pylori treatment: Antibiotics or probiotics. Applied Microbiology and Biotechnology. (2017). Link.
Lactobacilli infection case reports in the last three years and safety implications. Nutrients. (2022). Link.
Lactobacillus acidophilus DDS-1 and Bifidobacterium lactis UABla-12 Improve abdominal pain severity and symptomology in irritable bowel syndrome: Randomized controlled trial. Nutrients. (2020). Link.
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Probiotics supplementation during pregnancy or infancy on multiple food allergies and gut microbiota: A systematic review and meta-analysis. Nutrition Reviews. (2025). Link.
Role of Lactobacillus in the prevention of antibiotic-associated diarrhea: A meta-analysis. Pharmacotherapy. (2012). Link.
The effect of yogurt fortified with Lactobacillus acidophilus and Bifidobacterium sp. probiotic in patients with lactose intolerance. Food Science & Nutrition. (2021). Link.
The effects of the DDS-1 strain of lactobacillus on symptomatic relief for lactose intolerance – a randomized, double-blind, placebo-controlled, crossover clinical trial. Nutritional Journal. (2016). Link.
The efficacy of Lactobacillus acidophilus and rhamnosus in the reduction of bacterial load of Helicobacter pylori and modification of gut microbiota – a double-blind, placebo-controlled, randomized trial. Helicobacter. (2021). Link.
The functional roles of Lactobacillus acidophilus in different physiological and pathological processes. Journal of Microbiology and Biotechnology. (2022). Link.
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