Lactobacillus acidophilus

Written by: Kari Raman, PharmD, RPh
Published April 1, 2023

Lactobacillus acidophilus is a type of bacteria that naturally lives in healthy human bodies in the gut, mouth and even female reproductive parts. It’s also one of the most commonly used probiotic supplements. In the pharmacy, it’s one of the probiotics I get asked the most about. (It’s also known as L. acidophilus – read about how probiotics are named on our probiotic species page.)

Thankfully, there are a lot of clinical studies on Lactobacillus acidophilus.

What does Lactobacillus acidophilus do?

Clinical trials and research studies show some evidence supporting the potential benefits of Lactobacillus acidophilus as a probiotic, including improving gut health, enhancing immune function, reducing IBS symptoms, improving diarrhea and more.

Something I tell all my patients about probiotics though – results can vary depending on factors such as the strain, dosage, and everyone’s individual situation (and gut) are different. So while a study may show that L. acidophilus works great for a particular condition, that doesn’t mean that it will help any particular individual. And remember to see your primary care physician if you are having any serious health issues, including recurring diarrhea.

Clinical trial summary

There are many, many clinical trials studying Lactobacillus acidophilus. The best are what are called “double blind placebo” studies where some patients get the bacteria, and others just get sugar pills with no live bacteria, and then the results are compared. The double blind part means that the medical professionals conducting the study don’t even know who is getting the actual probiotic vs those who are getting dummy pills. Here are some findings from clinical trials and studies that suggest how L. acidophilus may work as a probiotic:


      1. Improving gut health: L. acidophilus can help maintain a healthy balance of gut flora by competing with and inhibiting the growth of harmful bacteria. It does this by producing lactic acid and other substances, which create an unfavorable environment for pathogenic bacteria. I’ll dive more into how it creates lactic acid.
      2. Potentially help with lactose intolerance: Because it digests lactose, it may help alleviate or reduce the symptoms of lactose intolerance for some people. But there isn’t a lot of research proving that it works well to treat lactose intolerance.
      3. Enhancing immune function: Some studies suggest that L. acidophilus may stimulate the immune system by interacting with immune cells and enhancing their activity. This can help the body better respond to infections and other challenges.
      4. Alleviating diarrhea: L. acidophilus has been shown in some studies to help reduce the duration and severity of diarrhea, particularly in cases of antibiotic-associated diarrhea. It may also help with traveler’s diarrhea. Of all of the benefits it may offer as a probiotic, there seems to be some pretty strong research suggesting that it can help.
      5. Reducing symptoms of irritable bowel syndrome (IBS): Some clinical trials have demonstrated that L. acidophilus may help alleviate IBS symptoms, such as abdominal pain, gas, bloating, and irregular bowel movements. There are quite a few studies that suggest that it can help SOME people who are suffering from IBS. But, there is no study that I’ve seen that really shows that it will cure IBS, only help with the symptoms. I was pretty excited to read a recent systematic review on probiotics and IBS, and there seems to be some emerging research that L. acidophilus is one probiotic that may help with IBS – but the review also strongly suggested combinations of probiotics, including this one, showed the highest chance of improvements. 
      6. Managing vaginal infections: Some research suggests that L. acidophilus can help prevent and treat vaginal infections, such as bacterial vaginosis and yeast infections, by maintaining a healthy balance of bacteria in the vaginal environment. But it’s unclear if taking it orally (as a pill that you eat) can help with this, or if you need to use it as a suppository.

    While there is real research supporting the potential benefits of L. acidophilus as a probiotic, more is needed to figure out optimal strains, dosages, and duration of treatment for different conditions. This is one of the strains that may be best to help deal with period symptoms like bloating; read more on my article “can you take probiotics while on your period.”  It is important to consult a healthcare professional before starting any probiotic supplementation, especially if you have a weakened immune system or other underlying health conditions.

    Lactobacillus acidophilus and lactose intolerance

    Lactose intolerance is one of the most common issues patients ask me about when they ask about L. acidophilus. This makes sense, as many gastrointestinologist will suggest lactic acid eating probiotics as a method to try to treat lactose intolerance.

    Here is the theory: milk has a sugar, lactose, that many people can not digest. This is due to not having enough lactase, an enzyme that breaks down lactose. As a result, people with lactose intolerance often experience stomach issues like bloating, gas, cramps, and diarrhea. Because some bacteria can actually break down lactose into other sugars that are easy for people to digest, it can reduce the symptoms of lactose intolerance. If you want to read about how lactose digested, scroll to the bottom of my article on the Lactobacillus species.

    So that’s the theory. I linked to research above that shows some studies impacting lactose intolerance – and they are mixed at best. So there is a chance that L. acidophilus could help for some people, but it’s not as good as another treatment I recommend to many patients, lactase enzyme like the ones made by Lactaid.

    How do you take Lactobacillus acidophilus?

    Always follow your doctor’s instructions, but generally, people taking L. acidophilus for digestive issues should take 1 to 15 billion colony forming units per day (CFUs). Depending on the probiotic, that will be one to several pills of it per day.

    Can you take L. acidophilus everyday?

    Yes, Lactobacillus acidophilus can generally be taken daily as a probiotic supplement or consumed through fermented foods containing live cultures, such as yogurt, kefir, or certain types of cheese. Taking L. acidophilus daily may help maintain a healthy balance of gut bacteria, support digestion, and potentially provide other health benefits.

    Always follow the recommended dosage instructions provided on probiotic supplements; and I strongly recommend talking with your doctor. The appropriate dosage may vary depending on factors such as age, health status, and specific health concerns.

    For most healthy individuals, daily consumption of L. acidophilus is considered safe. However, individuals with weakened immune systems or certain underlying medical conditions should consult their healthcare provider before starting any probiotic supplementation, as there may be potential risks or interactions.

    And taking pills is not the only way to get probiotics like L. acidophilus. Many healthy foods contain great probiotics – let’s dig into some that have this particular species.

    Where can you get it?

    L. acidophilus is in a number of supplements, including one that I recently reviewed Good Girl Proboitics. It’s also available in a number of other blends and stand alone supplements that you can get at drug stores and online. 

    Lactobacillus acidophilus in food

    Lactobacillus acidophilus is naturally present in some of the foods you eat – and some you may not have heard of. Honestly, I never ever had heard of kefir until I started researching probiotics! Foods with this probiotic, and many others, are usually produced through a process called fermentation, which involves the activity of beneficial bacteria, yeasts, or molds. Here’s a list of some foods that may contain L. acidophilus:

      1. Yogurt: Look for yogurt labeled with “live and active cultures” to ensure the presence of beneficial bacteria. Some list the bacteria species, others do not. One yogurt that contains this strain is Chobani, which I’ve written about. And you can read about how many probiotics yogurt contains here.

      1. Kefir: A fermented milk drink originating from the Caucasus region. It is made by adding kefir grains (a combination of lactic acid bacteria and yeasts) to milk, which results in a tangy, slightly carbonated beverage. Kefir often contains L. acidophilus and other beneficial bacteria.

      1. Acidophilus milk: Regular milk that has been fermented with L. acidophilus bacteria. It is sometimes called “sweet acidophilus milk” and can be found in some supermarkets or health food stores. I’ve never tried this one. Supposedly it’s pretty sour tasting, which makes sense if the bacteria has eaten all of the milk sugar.

      1. Miso: A traditional Japanese paste made from fermented soybeans, rice, or barley. Some miso products may contain L. acidophilus or other lactic acid bacteria, but the specific bacterial strains can vary depending on the fermentation process. I do like miso soup when I get sushi, and it turns out that if you prepare it without boiling it the bacteria stays alive.

      1. Sauerkraut: Fermented cabbage; great on sausage. I’ve for sure had this one.

    Overall, L. acidophilus is a very commonly taken probiotic that shows promise in helping a number of different conditions. I would generally feel good suggesting this probiotic to a healthy person in my pharmacy – but of course, if you are not feeling well or experiencing any serious conditions  you must talk to your doctor before starting any over the counter treatment such as a probiotic. 

    Pharmacist Kari Raman

    I’m Kari Raman PharmD, RPh, and I am a licensed, practicing pharmacist. I hold a Doctorate in Pharmacy from The University of the Pacific, and I’ve served patients in retail, compounding and hospital pharmacies.

    Probiotics are confusing!

    One of the most common questions I get asked by patients is about probiotics. And the truth is, probiotics are not as well understood by the healthcare community as they should be.

    So I’ve been reading a lot of probiotic clinical trials, and sharing what I’m learning here.

    I hope Pharmacist Probiotics helps you find out if there is a type of probiotic that works for you!