Natural Standard® Patient Monograph, Copyright © 2017 ( All Rights Reserved. Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.


Lactobacillus acidophilus is a member of the Lactobacillus genus of bacteria. These bacteria can be found in the mouth, intestine, and vagina. L. acidophilus is thought to benefit health, since it produces vitamin K and lactase. However, L. acidophilus cannot make many other vitamins and amino acids. Because of this, L. acidophilus is mostly found in the upper gastrointestinal (GI) tract where there are higher amounts of these nutrients.

L. acidophilus is commonly used in food, such as yogurt, other dairy products, and fermented soy products, such as miso and tempeh.

L. acidophilus is one of the most commonly used probiotics, microorganisms that are used to promote health. Probiotics are different from prebiotics, which are complex sugars that may support the growth of "good" bacteria in the intestinal tract. The word "synbiotic" means that a product has both a probiotic and a prebiotic.

There is good evidence for the use of L. acidophilus in treating vaginal infections. However, there is unclear evidence for other medicinal uses of L. acidophilus, such as in irritable bowel syndrome, brain disorders, asthma, high cholesterol, lactose digestion, or diarrhea.

Although it is thought to be safe with few side effects, L. acidophilus by mouth should be avoided in people who have intestinal damage, immune problems, or an overgrowth of bacteria in the intestines. These people may have a higher risk of having the bacteria leave the GI tract and possibly cause multiple organ failure. There have been reports that some Lactobacillus species, such as L. rhamnosus and L. casei, may be involved in infections, such as abscesses, meningitis, and septic arthritis.

This evidence-based monograph was prepared by The Natural Standard Research Collaboration