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Overview: Bacillus subtilis (B. subtilis) is a probiotic bacteria available over the counter as a supplement and in a food known as natto. It is commonly used to improve gut health and prevent certain infections, but its benefits are not well defined. Common side effects include gas and an upset stomach. Serious side effects are rare and include infections in some people who are at a high risk of infections. Before taking B. subtilis, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is Bacillus subtilis (B. subtilis) used for?

B. subtilis is a probiotic commonly used to improve gut health and prevent certain infections, but its benefits are not well defined.

Note: The FDA has not reviewed B. subtilis for safety and effectiveness. Learn more about dietary supplements here.

How does B. subtilis work (mechanism of action)?

B. subtilis 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 part of your microbiome. B. subtilis is naturally found in your gut. It is available as a dietary supplement and as part of a popular Japanese food known as natto. To make natto, soybeans are fermented with B. subtilis. One of the substances produced during this process, called nattokinase, is also available as a dietary supplement. Although B. subtilis is found in foods that contain natto, nattokinase supplements usually do not contain any bacteria.

B. subtilis makes many different substances and chemicals that can have effects in your gut. Some of these chemicals may help to reduce the amount of bad bacteria and increase the amount of good bacteria. When the microbiome in your gut is healthy, this can make you more able to digest foods and resist infections.

Unlike many other probiotics, B. subtilis can form spores. These are dormant, or “sleeping,” cells that can survive in harsh conditions. Some B. subtilis supplements contain spores because they are more likely to survive in the stomach than live bacteria. When the spores enter your intestine, they may “germinate” and turn into live bacteria. This can increase the levels of B. subtilis in your gut. But there are many different factors that can affect whether a probiotic survives in your body. When you take B. subtilis by mouth, it may not always survive long enough to germinate and multiply. As a result, its benefits are not well defined and may be different for each person. It is not clear whether B. subtilis can help with any health problems.

How should I store B. subtilis?

You should store B. subtilis 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.

Side Effects

What are the most common side effects of B. subtilis?

The most common side effects of B. subtilis 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 B. subtilis 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 B. subtilis?

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

Severe Allergic Reactions. B. subtilis may cause allergic reactions, which can be serious. Stop taking B. subtilis 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 B. subtilis, can get a serious infection. This happens when B. subtilis 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

Warnings & Precautions

Who should not use B. subtilis?

Allergies to Ingredients. People who are allergic to any of the following should not take B. subtilis.

  • B. subtilis
  • Bacillus subtilis
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific B. subtilis products they stock.

What should I know about B. subtilis before using it?

B. subtilis is a dietary supplement. It is also available in a specific type of food known as natto. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep B. subtilis out of the reach of children.

Premature infants can be at a greater risk of side effects from probiotics, such as B. subtilis. Talk to your health care provider about the risks if your infant was born prematurely.

Probiotics, such as B. subtilis, 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. Since bacteria slowly die off over time, the number of living bacteria in the product may be higher than the amount on the label. In products that contain B. subtilis spores, the CFU on the label tells you how many living bacteria are expected to come from those spores.

B. subtilis is a species of bacteria. Within that species are many different strains. Each strain of B. subtilis may have slightly different effects in the body. This means that some strains of B. subtilis may have certain effects that other strains do not have. If the product you are using contains a specific strain, it should be listed on the product label as a string of numbers or letters that come after "B. subtilis." If you switch to a different strain of B. subtilis, 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 B. subtilis 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 B. subtilis?

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 if B. subtilis 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 to your health care provider before taking B. subtilis. 

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

Other Medicines and Supplements. B. subtilis may interact with other medicines and supplements. Before taking B. subtilis, 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 B. subtilis could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

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

Interactions

Does B. subtilis interact with foods or drinks?

There are no known interactions between B. subtilis and foods or drinks.

It is unknown if drinking alcohol will affect B. subtilis.

Does B. subtilis 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 B. subtilis.

  • 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 B. subtilis and medicines are not fully understood. As with most dietary supplements, research on drug interactions with B. subtilis is incomplete. Always check with your health care provider before taking B. subtilis with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much B. subtilis?

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

B. subtilis is available as a dietary supplement in various strengths and dosage forms. Read the product label closely and speak to a health care provider about how to take B. subtilis safely. Do not take double or extra doses, even if you miss a dose.