Lactobacillus johnsonii
Lactobacillus johnsonii


Lactobacillus johnsonii (L. johnsonii) is a type of probiotic ("good" bacteria) found naturally in the human body. It's also found in fermented foods.

"Good" bacteria such as L. johnsonii might help the body break down food, absorb nutrients, and fight off "bad" organisms that might cause diseases. These bacteria are sometimes added to fermented foods like yogurt and also found in dietary supplements.

People use L. johnsonii for Crohn disease, hay fever, constipation, diarrhea, respiratory tract infections, and many other conditions, but there is no good scientific evidence to support these uses.

Don't confuse L. johnsonii with other probiotics, or with fermented food products such as fermented milk, kefir, or yogurt. These are not the same. Also note that the Lactobacillus genus was split up into 25 different genera in April 2020. Many species were reclassified at this time, but L. johnsonii remains in the Lactobacillus genus. Its name did not change. One specific strain of L. johnsonii, L. johnsonii La1 was previously known as L. acidophilus La1.
When taken by mouth: L. johnsonii is possibly safe for most people. L. johnsonii has been used safely in doses of up to 10 billion colony-forming units (CFUs) daily for up to 12 weeks or 4 billion CFUs daily for up to 6 months. It seems to be well-tolerated. But there isn't enough reliable information to know if heat-killed L. johnsonii is safe or what the side effects might be.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if L. johnsonii is safe to use when pregnant or breast-feeding. But there are no reasons to expect safety concerns when used appropriately.

Children: L. johnsonii is possibly safe in most children when taken by mouth appropriately. It's been used safely in infants in doses of about 10 billion colony-forming units (CFUs) daily in formula for 4 weeks. There isn't enough reliable information to know if L. johnsonii is safe for very small premature infants. Also, there isn't enough reliable information to know if heat-killed L. johnsonii is safe or what the side effects might be.

Weakened immune system: Probiotics have caused blood infections in a small number of people with weakened immune systems. If you have a weakened immune system, talk with your healthcare provider before taking probiotics, including L. johnsonii.

Damaged heart valves: Probiotic preparations can cause an infection in the inner lining of the heart chambers and heart valve. This is extremely rare, but people with damaged heart valves should stop taking probiotics, including L. johnsonii, before dental procedures or surgical procedures.


NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
  • A type of inflammatory bowel disease (Crohn disease). Taking L. johnsonii by mouth following surgery for Crohn disease doesn't seem to prevent recurrence in people with this condition.
There is interest in using L. johnsonii for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Insufficient evidence Effectiveness definitions

Dosing & administration

There isn't enough reliable information to know what an appropriate dose of L. johnsonii might be. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult a healthcare professional before using.

Interactions with pharmaceuticals

Antibiotic drugs

Interaction Rating=Moderate Be cautious with this combination.

L. johnsonii is a type of friendly bacteria. Antibiotics are used to reduce harmful bacteria in the body. Taking antibiotics along with L. johnsonii can reduce the effects of L. johnsonii. To avoid this interaction, take L. johnsonii products at least 2 hours before or after antibiotics.

Interactions with herbs & supplements

There are no known interactions with herbs and supplements.

Interactions with foods

There are no known interactions with foods. has licensed monographs from TRC Healthcare.
This monograph was last reviewed on 22/02/2023 11:00:00. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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