Overview

Lactobacillus acidophilus (L. acidophilus) is a probiotic bacteria that is available over the counter as a supplement. It is also found in some fermented foods and yogurts. L. acidophilus is commonly used to improve gut and digestive health, but its benefits are not well defined. Common side effects include gas and upset stomach. Serious side effects are rare but may include infections in some people who are at high risk for infections. Before taking L. acidophilus, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is Lactobacillus acidophilus (L. acidophilus) used for?

L. acidophilus is a probiotic. It is commonly used to improve gut and digestive health. For example, people often use it to prevent or treat diarrhea that can happen from antibiotics or other causes, for irritable bowel syndrome (IBS), or for other digestive issues. However, its benefits are not well defined.

L. acidophilus may also be used for other conditions as determined by your health care provider.

L. acidophilus is available as a dietary supplement in various strengths and dosage forms. Some dietary supplements that contain L. acidophilus also contain many other ingredients, including other probiotics.

Note: The FDA has not reviewed L. acidophilus products for safety and effectiveness. Learn more about dietary supplements here.

How does L. acidophilus work (mechanism of action)?

L. acidophilus is a species of bacteria. It is a type of probiotic, which means it is a live microbe that may provide health benefits in some people.

Your gut is home to millions of different microbes, which make up your gut microbiome. L. acidophilus is naturally found in your mouth and gut. You can also get L. acidophilus from dietary supplements and some of the foods that you eat, such as kefir, sauerkraut, kimchi, and certain types of yogurt.

L. acidophilus makes a substance called lactic acid. Lactic acid can help improve the health of your microbiome by reducing the amount of bad bacteria and increasing the amount of good bacteria. When your gut microbiome is healthy, it can improve your ability to digest foods and resist infections. L. acidophilus can also make an enzyme called lactase. This enzyme can help break down lactose, the sugar in milk products that causes lactose intolerance in some people.

Taking L. acidophilus increases the levels of this bacteria in your gut. This may help improve the health of your microbiome and also improve symptoms of lactose intolerance in some people. But there are many different factors that can affect whether a probiotic survives in your gut. When you take L. acidophilus by mouth, it may not always survive long enough to grow and multiply in your gut. As a result, its benefits for gut health are not well defined and may be different for each person.

How should I store L. acidophilus?

You should store L. acidophilus according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight. Some L. acidophilus products should be stored in the refrigerator, between 36 F and 46 F (2 C and 8 C), after they are opened. Follow the instructions on the label of the product you are using.

Side Effects

What are the most common side effects of L. acidophilus?

The most common side effects of L. acidophilus are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Gas
• Upset stomach

There may be other side effects of L. acidophilus that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of L. acidophilus?

While less common, the most serious side effects of L. acidophilus are described below, along with what to do if they happen.

Severe Allergic Reactions. L. acidophilus may cause allergic reactions, which can be serious. Stop taking L. acidophilus and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Serious Infections. In very rare cases, some people who take probiotics, such as L. acidophilus, can get a serious infection. This happens when L. acidophilus moves into a part of the body where it is not supposed to be, such as your blood. This is most likely to happen in people who are very sick or who have very weak immune systems, such as people with cancer or who are receiving chemotherapy. Call your health care provider right away if you have any of the following symptoms.

• Fever, sweats, chills, or muscle aches
• Tiredness
• Shortness of breath
• Fast heartbeat

Precautions

Who should not use L. acidophilus?

Allergies to Ingredients. People who are allergic to any of the following should not take L. acidophilus.

• Acidophilus
• L. acidophilus
• Lactobacillus acidophilus
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific L. acidophilus products they stock.

What should I know about L. acidophilus before using it?

If L. acidophilus was prescribed to you by a health care provider, take it as prescribed. If you are taking L. acidophilus as an over-the-counter supplement, follow the instructions that come with the product or take it as your health care provider recommends. If you have any questions about how to take L. acidophilus, talk to your health care provider.

Do not share L. acidophilus that was prescribed for you by a health care provider with other people, even if they have the same condition as you. It may harm them.

Keep L. acidophilus out of the reach of children. Because some L. acidophilus products should be kept in a refrigerator, take special precautions to keep them away from children who also use the refrigerator.

Premature infants can be at greater risk for side effects from probiotics such as L. acidophilus. Talk to your health care provider about the risks if your infant was born prematurely.

Probiotics, such as L. acidophilus, are usually measured in colony-forming units (CFUs). Each CFU is equal to one living bacteria. The number of CFUs listed on the product label tells you how many living bacteria should be in that product on the day that it expires. Because bacteria slowly die off over time, the number of living bacteria in the product may be higher than the amount on the label.

Many probiotic products contain multiple different species of microbes. Different microbes can have different effects in the body. It is important to read the product label closely to understand which species of bacteria are in that product.

L. acidophilus is a species of bacteria. Within that species are many different strains. Each strain of L. acidophilus may have slightly different effects in the body. This means that some strains of L. acidophilus may have certain effects that other strains do not. If the product you are using contains a specific strain, it should be listed on the product label as the string of numbers or letters that come after “L. acidophilus.” If you switch to a different strain of L. acidophilus, it may not have the same effects or side effects. Talk to your health care provider if you have questions or concerns.

Some probiotic products have been found to contain other microbes that are not listed on the label and that may cause serious health problems. The FDA has not tested L. acidophilus products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using L. acidophilus?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know whether L. acidophilus is right for you.

In particular, make sure that you discuss any of the following.

Central Line or Port.A central venous catheter (central line) or port is a small tube placed into a vein that can be used to give medicines and fluids directly into the vein (intravenously, or IV). These tubes can become infected by microbes, including probiotics. If you have a central line or port, speak with your health care provider before taking L. acidophilus.

Other Current and Past Health Conditions.Tell your health care provider if you have any of the following.

• An autoimmune condition
• Cancer
• Immune problems, such as a weak immune system

Other Medicines and Supplements.L. acidophilus may interact with other medicines and supplements. Before taking L. acidophilus, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how L. acidophilus could affect pregnancy or harm an unborn baby. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if L. acidophilus passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does L. acidophilus interact with foods or drinks?

There are no known interactions between L. acidophilus and foods or drinks.

It is unknown if drinking alcohol will affect L. acidophilus.

Does L. acidophilus interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking L. acidophilus.

• A medicine that suppresses the immune system
• An antibiotic, which is used to treat certain bacterial infections
• Chemotherapy, which is used to treat certain cancers

The interactions between L. acidophilus and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with L. acidophilus is incomplete. Always check with your health care provider before taking L. acidophilus with any medicines.

Dosing

What should I do if I accidentally use too much L. acidophilus?

If you or someone else has used too much L. acidophilus, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

L. acidophilus products may contain many different ingredients, including other probiotics. Read the product label closely and speak with a health care provider about how to take L. acidophilus safely. Do not take double or extra doses, even if you miss a dose.