Lactobacillus acidophilus


Lactobacillus acidophilus is one of the most prominent strains of beneficial bacteria that predominantly reside in the small intestine. They provide a number of beneficial functions and effects such as prevention of bacterial infections, enhancement of digestion and absorption of nutrients, metabolism of cholesterol, and a strengthening of the immune system. Maintaining a healthy colonization of intestinal microflora with beneficial bacteria such as L. acidophilus is a key factor in an individual’s overall health.

Dosage Info

Dosage Range

From 1-2 billion cfu (colony forming units) daily for maintenance. Doses up to 10 billion cfu daily for approximately two weeks are recommended to recolonize the intestinal microflora following antibiotic therapy.

Most Common Dosage

10 billion cfu daily.

Dosage Forms

Capsules, tablets, and bulk powder.

Adult RDI

None established

Adult ODA

None established


  • : None established

Interactions and Depletions


Active Forms

Lactobacillus acidophilus.


L. acidophilus bacteria are not absorbed, but rather remain within the gastrointestinal tract. In order to be effective, L. acidophilus organisms must survive the acidity of the stomach. The acidity of the empty stomach ranges from a pH of 1 to 2. However, after eating, the stomach contents are diluted with food, which raises its pH to around 4. It has been reported that after food consumption, the stomach contents become less acidic due to their dilution by food (around pH 4), which allows greater numbers of L. acidophilus bacteria to successfully survive the diluted stomach acids and pass through the stomach into the small intestine. (1)

Toxicities & Precautions


There is no known toxicity associated with L. acidophilus.

Functions in the Body

Enzyme Activity

Produces enzymes such as proteases, lipases, and lactase, which aid in the digestion of proteins, fats, and milk products.

Immune System

Produces hydrogen peroxide, which has a wide range of activity against yeasts, molds, and bacteria. They adhere to the intestinal mucosa, which helps prevent pathological bacteria from colonizing, produce lactic acid, which creates an acidic environment that is unfavorable for pathogens, and help activate macrophages (immune cells).


The production of lactic acid by L. acidophilus bacteria creates a slightly acidic pH in the small intestine, which inhibits the growth of pathological organisms and enhances the absorption of minerals such as calcium and iron.

Anti-infection Activity

Various strains of L. acidophilus produce natural antibiotics (acidophilin, lactocidin, lactobicillin, lactobreven) in the gastrointestinal tract. It has been reported that these natural antibiotics can inhibit the growth of 23 toxin producing organisms.


Helps to lower cholesterol by converting it to a less absorbable form known as coprostanol, which inhibits its absorption from the intestinal tract.

Clinical Applications

Elevated Cholesterol

Ingestion of acidophilus-containing yogurt resulted in approximately a 2 to 3 percent lowering of cholesterol. Since every 1 percent reduction in serum cholesterol concentration is associated with an estimated 2 to 3 percent reduction in risk for coronary heart disease, regular intake of an appropriate strain of L. acidophilus has the potential of reducing risk for coronary heart disease by 6 to 10 percent. (2)

Vaginal Candidiasis

L. acidophilus therapy has been reported to be helpful in the prevention and treatment of vaginal candidiasis infections. (3)

Reduce Cancer Risk

Researchers found that administration of Lactobacillus acidophilus reduced DNA damage in colon cells indicating a reduced risk of colon cancer. (4)

Infantile Diarrhea

Infants treated with Lactobacillus acidophilus plus rehydration therapy recovered more quickly than those treated with other protocols that did not contain acidophilus. (5)

Antibiotic Therapy

Researchers report that ingestion of lactic acid-producing bacteria substantially reduce the incidence of antibiotic-induced diarrhea. (6) , (7)

Enhanced Immunity

Volunteers taking an acidophilus supplement for 3 weeks recorded a doubling of their phagocytic index. Six weeks after discontinuing the supplement, the activity of their phagocytes was still 50 percent higher than it was at the start of the experiment. (8)

Lactose Intolerance

Ingestion of acidophilus by lactose intolerant humans results in improved lactose digestion as evidenced by improved symptoms and a decrease in hydrogen excreted in their breath. (9)

Symptoms and Causes of Deficiency

A deficiency of L. acidophilus bacteria can result in the growth and proliferation of pathological organisms in the intestinal tract. This can decrease digestion and absorption of nutrients, as well as increase production of gas, bloating, and toxins. The most common cause of a deficiency of L. acidophilus bacteria is the use of antibiotic drugs. Other factors that can cause a reduction of L. acidophilus include the use of drugs that increase intestinal pH, stress, diarrhea, intestinal infections, and the presence of toxins in the intestine.

Dietary Sources

Small amounts of L. acidophilus occur in cultured food products such as yogurt and acidophilus milk. However, in order to be effective, larger quantities need to be consumed in the form of supplements.


  1. View Abstract: Robins-Brown RM, Levine M. The Fate of Ingested Lactobacilli in the Proximal Small Intestine. Am J Clin Nutr. 1981;34:514-19.
  2. View Abstract: Anderson JW, et al. Effect of Fermented Milk (yogurt) Containing Lactobacillus Acidophilus L1 on Serum Cholesterol in Hypercholesterolemic Humans. J Am Coll Nutr. Feb1999;18(1):43-50.
  3. View Abstract: Elmer GW, et al. Biotherapeutic Agents. A Neglected Modality for the Treatment and Prevention of Selected Intestinal and Vaginal Infections. JAMA. Mar1996;275(11):870-76.
  4. View Abstract: Oberreuther-Moschner DL, Jahreis G, Rechkemmer G, Pool-Zobel BL. Dietary intervention with the probiotics Lactobacillus acidophilus 145 and Bifidobacterium longum 913 modulates the potential of human faecal water to induce damage in HT29clone19A cells. Br J Nutr. Jun2004;91(6):925-32.
  5. View Abstract: Michielutti F, et al. Clinical Assessment of a New Oral Bacterial Treatment for Children with Acute Diarrhea. Minerva Med. Nov1996;87(11):545-50.
  6. Katagiri S. Study on the Anti-diarrhea Effect-conbined Use of Augmentin and Lactic Acid Bacteria Product of Multiple Resistance. Basics and Clinics. Dec1986;20(17):651-53.
  7. View Abstract: Cremonini F, Di Caro S, Santarelli L, et al. Probiotics in antibiotic-associated diarrhoea. Dig Liver Dis. Sep2002;34 Suppl(2):S78-80.
  8. View Abstract: Schiffrin EJ, et al. Immune Modulation of Blood Leukocytes in Humans by Lactic Acid Bacteria: Criteria for Strain Selection. Am J Clin Nutr. Aug1997;66(2):515S-20S.
  9. View Abstract: Kim HS, et al. Lactobacillus Acidophilus as a Dietary Adjunct for Milk to Aid Lactose Digestion in Humans. J Dairy Sci. May1983;66(5):959-66.