What Is Lactobacillus Acidophilus?

A bacteria that promotes gut health and helps prevent infections

Found naturally in your intestines, Lactobacillus acidophilus is one of the best-known probiotics—beneficial microorganisms that may promote health and protect against infections.

Lactobacillus acidophilus balances potentially harmful bacteria that can otherwise flourish in the gut due to illness or antibiotics. It may also help balance flora in the vagina, helping to prevent yeast infections.

Commonly found in yogurt and other fermented foods, it is also available in supplement form.

Sauerkraut, cucumber pickles and yogurt
marekuliasz / Getty Images

Also Known As

  • Acidophilus
  • L. acidophilus

What Is Lactobacillus Acidophilus Used For?

L. acidophilus belongs to the Lactobacillus family of bacteria. Lactic acid bacteria (or L) converts sugars into lactic acid and hydrogen peroxide, substances that inhibit the growth of undesirable bacteria in the intestines.

In alternative medicine, acidophilus is sometimes used to prevent or treat several health conditions, including:

Some proponents also claim that acidophilus can promote weight loss and strengthen the immune system.

Although acidophilus is one of the more extensively studied probiotics, findings have varied widely due to differences in patient populations, acidophilus strains, and other factors.

Here's a look at some findings from the available research on the benefits of Lactobacillus acidophilus.


Acidophilus may be recommended as a potential treatment for diarrhea. In particular, research suggests it may help to prevent C. difficile-associated diarrhea, a type of severe diarrhea that often affects older adults in medical care facilities who require broad-spectrum antibiotic treatment.

In a research review published in the Cochrane Database of Systematic Reviews in 2017, scientists analyzed 31 previously published trials on the use of various types of probiotics to prevent C. difficile-associated diarrhea.

It concluded that short-term, prophylactic use of probiotic supplements while taking broad-spectrum antibiotics is safe and effective for preventing C. diff infections in people who do not have weakened immune systems or are not severely debilitated.

Probiotics have also been found to be potentially useful in treating diarrhea from other causes as well. One study, which focused on probiotic use in children under 2 years of age with rotavirus, found acidophilus and other probiotics significantly reduced the duration of diarrhea compared to a placebo.

An older review of published research found probiotics may be effective in reducing the severity of traveler's diarrhea, antibiotic-related diarrhea, and acute diarrhea of other causes.

Additional research found acidophilus and other probiotics may reduce diarrhea caused by radiation treatments, a common side effect of pelvic radiotherapy.

Irritable Bowel Syndrome

Probiotics including acidophilus have been touted as a treatment for irritable bowel syndrome (IBS). However, the research is mixed.

One eight-week study of people with IBS found a probiotic combination of L. acidophilus and Bifidobacterium lactis noticeably relieved IBS symptoms at four and eight weeks compared to a placebo. But a six-month clinical trial found a combination of probiotics that included acidophilus had no beneficial effect on diarrhea in people with IBS.

Still another study found the probiotics appear to work best to relieve symptoms of IBS when they are taken in single strain doses of less than 10 billion colony-forming units (CFUs) per day for less than eight weeks.

Vaginal Health

L. acidophilus may be helpful in the prevention and treatment of vaginal infections. According to a 2014 review, Lactobacillus supplements (including acidophilus) taken daily may help prevent and treat bacterial vaginosis, a common vaginal infection that results from an imbalance in the types of bacteria (flora) in the vagina.

Acidophilus is commonly recommended for the prevention of yeast infections while taking antibiotics. Laboratory research shows the probiotic inhibits the growth of Candida albicans in cell cultures, but little research has been done in humans.

A 2015 clinical trial published in the journal Probiotics and Antimicrobial Proteins found L. acidophilus can help to prevent recurring yeast infections following standard medical treatment.

In the study, 436 people assigned female at birth with vaginal candidiasis were treated with the antifungal fenticonazole. Five days later, roughly half the subjects were treated with multiple intravaginal L. acidophilus treatments. Those given the probiotic had a significant reduction in recurring infections.

Immune Health

Acidophilus has antimicrobial and antiviral properties and may help to prevent colds, viruses, and even allergies. There is research to suggest probiotics, including acidophilus, may reduce cold symptoms in children.

A study published in the journal Pediatrics found six months of daily L. acidophilus probiotics reduced fever by 53%, coughing by 41%, antibiotic use by 68%, and days absent from school by 32%. Combining acidophilus with a broad spectrum of probiotics was found to be even more effective.

High Cholesterol

Studies suggest that probiotics may help cut cholesterol levels, and acidophilus appears to be more effective than other species.

A 2015 literature review published in the Annals of Medicine concluded that probiotic supplements containing L. acidophilus were effective in lowering total cholesterol and LDL ("bad") cholesterol levels.

The review of 15 studies involving 788 subjects also found the probiotic improved factors associated with cardiovascular disease, including waist circumference and inflammatory markers. Compared to other strains, acidophilus was found to be more effective in reducing LDL levels.

These results were confirmed in a review published in the journal Medicine in 2015. Researchers analyzed 30 randomized controlled trials with 1,624 participants and found probiotics lowered total cholesterol and LDL cholesterol by 7.8 mg/dL and 7.3 mg/dL, respectively.

The study authors noted, however, that many studies showing the strongest connection were funded by supplement companies and more independent research is needed.

Weight Loss

Some probiotic proponents claim that supplementing with probiotics like L. acidophilus can promote weight loss, but the research is conflicting. While it shows promise in animal trials, human trials have inconclusive results.

The best researched and seemingly effective probiotic strain for weight loss is Lactobacillus gasseri. In a 2013 study published in The British Journal of Nutrition, 210 adults with abdominal fat were assigned to drink 7 ounces of fermented milk with either 1 billion, 10 billion, or 0 CFU of L. gasseri a day for 12 weeks.

At the end of the study, abdominal fat was reduced by more than 8% in the probiotic groups compared to the control group. Additional measures, such as body mass index (BMI), waist-to-hip ratio, and total body fat, were also significantly reduced in those drinking fermented milk with L. gasseri.

Body Mass Index

BMI is a dated, flawed measure. It does not take into account factors such as body composition, ethnicity, sex, race, and age.

Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.


Various probiotics are being studied for their potential to reduce blood sugar in people with diabetes. It is believed that the beneficial bacteria may improve carbohydrate metabolism.

A 2016 review of seven published studies of people with type 2 diabetes found those who took probiotics for at least eight weeks decreased fasting blood sugar by 16 mg/dl and A1C levels by 0.53 percentage points compared to placebo groups. Subjects taking a broad spectrum of probiotics experienced a 35 mg/dl drop in fasting glucose levels.

The research focused on various probiotics; it is unclear if acidophilus alone is beneficial for blood sugar management.


Emerging research suggests probiotics including L. acidophilus may help prevent and treat depression. Scientists have found a link between the gut and emotional health, and taking probiotics may improve intestinal health.

A 2016 literature review published in the journal Nutrients found that probiotics were associated with a significant reduction in depression and should be studied further as a potential preventive strategy for the condition.

Possible Side Effects

Common side effects include digestive complaints, such as gas, bloating, upset stomach, or diarrhea. Although most digestive side effects decrease with use, if they do not improve or worsen, you should discontinue L. acidophilus and consult a healthcare provider.

In addition to this, acidophilus may weaken tooth enamel over time when exposed to teeth.

Serious side effects are rare. However, if you experience hives, skin rash, itching, difficulty breathing, vomiting, or swelling of your face, lips, tongue, or throat, stop using L. acidophilus and seek immediate medical attention.

Special Considerations

If you are pregnant, breastfeeding or chestfeeding, speak to a healthcare provider before taking acidophilus.

You should consult a pediatrician before giving acidophilus to children, babies, or infants. Children who are ill, premature infants, and children with weakened immune systems are at a greater risk for adverse events and complications.

There's some concern that acidophilus can raise the risk of D-lactate toxicity. People who have had gastric bypass surgery or who have any of the following issues may be at greater risk:


People with a weak or impaired immune system due to a medical condition, or immune-suppressing treatment or medication, should not take acidophilus.

Likewise, you should not take acidophilus if you have an artificial heart valve, heart valve disorder, or central venous catheter due to the risk of infection.

You will also need to avoid acidophilus if you have a condition resulting in intestinal damage, due to the risk that the bacteria could escape into other parts of the body and potentially cause serious complications such as bacteremia or sepsis. There have been reports of other Lactobacillus species being involved in infections such as abscesses and meningitis.

Dosage and Preparation

Acidophilus supplements are sold in a variety of forms: capsules, tablets, drinks, pearls, powders, chewable wafers, liquids, and suppositories.

The typical adult dose is 1 to 10 billion living organisms known as colony-forming units (CFUs), taken in up to four divided doses. Follow the directions on the packaging or speak to a healthcare provider about the appropriate dose for you.

If giving L. acidophilus to a child, check with a pediatrician about an appropriate dose or purchase a brand formulated for children and follow the directions on the packaging.

Depending on the manufacturing processes, you may find some probiotics need refrigeration while others are shelf-stable. Be sure to store probiotics as directed on the label and minimize contact with air.  

What to Look For

Lactobacillus acidophilus products are available at health-food stores, supermarkets, drugstores, and online.

Just as there are several forms of acidophilus, there is a variety of formulations as well. You may benefit from reading labels and looking for two things in particular:

  • Strains: Some acidophilus products contain a single strain of the bacteria, while others contain a number of different strains or species. There are many different strains of probiotics that have similar health benefits as acidophilus. Look for a broad-spectrum option that includes L. acidophilus.
  • Pectin: Some acidophilus supplements contain pectin, a soluble fiber found in citrus and other fruits. Proponents claim that the pectin is a prebiotic (a substance that promotes the growth of probiotic bacteria).

Some probiotic supplements may contain milk allergens or traces of lactose. If you are allergic to milk proteins or lactose intolerant, or if this is of concern because you are vegan, look for a formulation that is labeled "dairy-free."

Unlike prescription and over-the-counter drugs, the U.S. Food and Drug Administration (FDA) doesn't regulate probiotics or test them for safety. Some products may contain fewer than the stated number of live organisms. Other products may be contaminated with other bacterial strains or ingredients.

To ensure you are getting a quality product, look for a trusted independent, third-party seal on the label, such as U.S. Pharmacopeia, NSF International, or ConsumerLab, etc. This can at least give you peace of mind that what is on the product label is what is in the product itself.

Food Sources

Lactic acid bacteria are used in the making of many foods, including yogurt, kefir, and buttermilk. Acidophilus, in particular, can be found in yogurt that is made with live acidophilus cultures, as well as other fermented milk products such as kefir.

Other sources of acidophilus include:

  • Kimchi (a traditional Korean fermented cabbage dish)
  • Kombucha (a fermented tea)
  • Sour pickles
  • Sauerkraut
  • Sourdough bread
  • Fermented soy products such as miso and tempeh

The number of live organisms varies greatly from option to option due to differences in processing methods. Look for products sold in the refrigerated section of the grocery or health-food store, which are more likely to contain live cultures than those stored at room temperature.

A Word From Verywell

The current research on acidophilus is inconclusive as most studies have used a unique combination of probiotics or different doses, making it difficult to determine its effectiveness and standardized dosing.

While acidophilus may seem harmless because it is found naturally in the body and in many common foods, supplementation isn't right for everyone. If you're considering taking acidophilus for any condition, it's a good idea to consult with a healthcare provider to confirm if it's appropriate and safe for you.

Frequently Asked Questions

  • Can you take lactobacillus acidophilus every day?

    Yes, in fact it is generally recommended to take a probiotic such as lactobacillus acidophilus daily for improved digestion and overall health. 

  • What are the side effects of probiotics?

    Side effects of probiotics mostly include digestive complaints. Gas, bloating, upset stomach, and diarrhea are common complaints when people first start taking probiotics. These side effects usually go away after regular use. 

  • How much L. acidophilus should I take?

    The typical adult dose of L.acidophilus is 1 to 10 billion CFUs, or colony-forming units (CFUs) a day, split into four doses.

  • What foods contain acidophilus?

    Foods that contain acidophilus include yogurt made with live active cultures, kombucha, kimchi, sour pickles, sauerkraut, sourdough bread, miso, and tempeh.

22 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Guo H, Zheng Y, Wang B, Li Z. A Note on an Improved Self-Healing Group Key Distribution Scheme. Sensors (Basel). 2015;15(10):25033-8.  doi:10.3390/fermentation5020041

  2. Goldenberg JZ, Yap C, Lytvyn L, et al. Probiotics for the prevention of Clostridium difficile-associated diarrhea in adults and children. Cochrane Database Syst Rev. 2017;12:CD006095. doi:10.1002/14651858.CD006095.pub4.

  3. Understanding the health benefits of taking probiotics. Harvard Medical School. March 2014.

  4. Schettle L, Lio PA. Probiotics: The Search for Bacterial Balance. National Eczema Association.

  5. Grandy G, Medina M, Soria R, Terán CG, Araya M. Probiotics in the treatment of acute rotavirus diarrhoea. A randomized, double-blind, controlled trial using two different probiotic preparations in Bolivian children. BMC Infect Dis. 2010;10:253. doi:10.1186/1471-2334-10-253

  6. Sazawal S, Hiremath G, Dhingra U, Malik P, Deb S, Black RE. Efficacy of probiotics in prevention of acute diarrhoea: a meta-analysis of masked, randomised, placebo-controlled trials. Lancet Infect Dis. 2006;6(6):374-82. doi:10.1016/S1473-3099(06)70495-9

  7. Chitapanarux I, Chitapanarux T, Traisathit P, Kudumpee S, Tharavichitkul E, Lorvidhaya V. Randomized controlled trial of live lactobacillus acidophilus plus bifidobacterium bifidum in prophylaxis of diarrhea during radiotherapy in cervical cancer patients. Radiat Oncol. 2010;5:31. doi:10.1186/1748-717X-5-31

  8. Ringel-Kulka T, Palsson OS, Maier D, et al. Probiotic bacteria Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi-07 versus placebo for the symptoms of bloating in patients with functional bowel disorders: a double-blind study. J Clin Gastroenterol. 2011;45(6):518-25. doi:10.1097/MCG.0b013e31820ca4d6

  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

  10. Zhang Y, Li L, Guo C, et al. Effects of probiotic type, dose and treatment duration on irritable bowel syndrome diagnosed by Rome III criteria: a meta-analysis. BMC Gastroenterol. 2016;16(1):62. doi:10.1186/s12876-016-0470-z

  11. Homayouni A, Bastani P, Ziyadi S, et al. Effects of probiotics on the recurrence of bacterial vaginosis: a review. J Low Genit Tract Dis. 2014;18(1):79-86.  doi:10.1097/LGT.0b013e31829156ec

  12. Matsubara VH, Wang Y, Bandara HM, Mayer MP, Samaranayake LP. Probiotic lactobacilli inhibit early stages of Candida albicans biofilm development by reducing their growth, cell adhesion, and filamentation. Appl Microbiol Biotechnol. 2016;100(14):6415-26.  doi:10.1007/s00253-016-7527-3

  13. Kovachev SM, Vatcheva-Dobrevska RS. Local Probiotic Therapy for Vaginal Candida albicans Infections. Probiotics Antimicrob Proteins. 2015;7(1):38-44. doi:10.1007/s12602-014-9176-0.

  14. Leyer GJ, Li S, Mubasher ME, Reifer C, Ouwehand AC. Probiotic effects on cold and influenza-like symptom incidence and duration in children. Pediatrics. 2009;124(2):e172-9. doi:10.1542/peds.2008-2666

  15. Sun J, Buys N. Effects of probiotics consumption on lowering lipids and CVD risk factors: a systematic review and meta-analysis of randomized controlled trials. Ann Med. 2015;47(6):430-40.  doi:10.3109/07853890.2015.1071872

  16. Cho YA, Kim J. Effect of Probiotics on Blood Lipid Concentrations: A Meta-Analysis of Randomized Controlled Trials. Medicine (Baltimore). 2015;94(43):e1714. doi:10.1097/MD.0000000000001714.

  17. Kadooka Y, Sato M, Ogawa A, et al. Effect of Lactobacillus gasseri SBT2055 in fermented milk on abdominal adiposity in adults in a randomised controlled trial. Br J Nutr. 2013;110(9):1696-703.  doi:10.1017/S0007114513001037

  18. Zhang Q, Wu Y, Fei X. Effect of probiotics on glucose metabolism in patients with type 2 diabetes mellitus: A meta-analysis of randomized controlled trials. Medicina (Kaunas). 2016;52(1):28-34.  doi:10.1016/j.medici.2015.11.008

  19. Huang R, Wang K, Hu J. Effect of Probiotics on Depression: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2016;8(8).  doi:10.3390/nu8080483

  20. Karlsson S, Brantsæter AL, Meltzer HM, Jacobsson B, Barman M, Sengpiel V. Maternal probiotic milk intake during pregnancy and breastfeeding complications in the Norwegian Mother and Child Cohort Study. Eur J Nutr. 2019. doi:10.1007/s00394-019-02072-8

  21. Taking Medications: What You Need to Know to Stay Safe. Cleveland Clinic. March 2014.

  22. Microorganisms & Microbial-Derived Ingredients Used in Food (Partial List). US Food & Drug Administration. January 2018.

Additional Reading

By Cathy Wong
Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.