What is Acidophilus?

What is Acidophilus?

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:

Thanks to the University of North Carolina School of Pharmacy for the use of this article!

Stew Eckard and Mike Darnofall


  • natural flora of the Gastrointestinal and Genitourinary tracts

Dietary Sources:

  • Yogurt
  • Cheese
  • Miso
  • Tempeh
  • other fermented dairy products

Deficiency Signs and Symptoms:

  • there are no specific signs or symptoms designating that one is deficient in Acidophilus
  • there is an increased risk of various GI infections
  • can be destroyed by…
  • -stress, poor dietary habits, chlorinated and flouridated water, birth control pills, antibiotics

Principle Uses/Beneficial Effects:

1.  Promotion of Proper Intestinal Environment

  • Colonization of friendly bacteria inhibits growth of other pathogens by competing for nutrients and adhesion sites, altering acidity and oxygen levels, and producing bacteriocins, H2O2, and other metabolic end products such as lactic and acetic acid

2.  Lactose Intolerance

  • Lactobacilli produce the enzyme (-galactosidase which metabolizes the milk sugar lactose

3.  Post-antibiotic Activity

  • Recolonization with probiotics may prevent pathogenic diarrhea resultant from a disturbance of the normal flora
  • May also prevent colonization of pathogens that would cause a recurrent or secondary infection

4.  Vaginal Yeast infections

  • Benefits from 1 and 3

5.  Urinary Tract infections

  • Benefits from 1 and 3

6.  Cancer Prevention/ ADR's of radiation treatment

  • Lactobacilli may reduce activity of bacterial enzymes associated with the formation of cancer-causing compounds in the gut
  • Reduced post radiation diarrhea via benefits from 3

7.  Cholesterol Effects

  • Mutant strain may produce hydroxymethylglutarate-an inhibitor of HMG CoA reductase

Available Forms:

Acidophilus can come in a variety of formulations, particularly in fermented foods, but also in manufactured products. However, the level of viability may be compromised in many of these products. Some products such as yogurt may not be colonized with the acidophilus form of lactobacillus; there are many other strains that may not have the same beneficial effects. Furthermore, various forms of manufacturing, packaging, and storage may reduce viability. There are also various strains within the acidophilus species, some of which are weaker than others. Typically, high quality commercial preparations will produce greater colonization than just plain yogurt.

  • tablets
  • capsules
  • granules
  • powders
  • fermented dairy products

Dosage Ranges:

  • ~1 to 10 billion viable organisms daily is generally sufficient
  • larger amounts may produce GI disturbances
  • topical douche: 108 live organisms/ml X 10 ml BID
  • post-antibiotic: may need at least 15 to 20 billion organisms

Safety Issues:

  • Very safe
  • Not associated with any side effects


  • Negatively affected by antibiotics, OCP's, and alcohol
  • Interferes with metabolism of sulfasalazine, chloramphenicol palmitate, and phthalylsulfathiazole

Clinical Trials:

I.  Preservation of Intestinal Integrity During Radiotherapy Using Live L. Acidophilus Cultures (Salminen et al)

  • Pilot study of 21 females with cervical or uterine carcinoma receiving external and internal radiotherapy (RT)
  • 40-75 yo with similar body mass index; diabetes and GI disorders excluded
  • Randomized into 2 groups:
    • Control group (10) received dietary counseling only (low fat/low residue diet with adequate protein/carbohydrates; avoid "gassy" foods)
    • Test group (11) received dietary counseling plus 150 mL milk/day (containing at least 2 billion live L. acidophilus) plus 6.5% lactulose substrate
  • Duration of study:  began 5 days before RT, continued throughout RT, then for 10 days after RT
  • Patients were interviewed before, during, and 6 weeks after treatment (questions included subjective feelings, GI disturbances, abdominal pain, use of anti-diarrheals/laxatives)


  • Controls all suffered from pronounced diarrhea throughout RT, and used more anti-diarrheals
  • Test Subjects suffered only occasional diarrhea of a transient nature.  The incidence of diarrhea was significantly smaller in the test group (p<0.01)
  • Both groups experienced similar amounts of related GI disturbances

II.  Inhibition of Candida Albicans by L. Acidophilus (Collins/Hardt)

  • Three month randomized study of 30 women infected with C. Albicans
  • Each volunteer given a 10-day supply of Nystatin and randomly assigned to a group receiving no milk products (control) or one of the following:
    • nonfermented acidophilus milk
    • yogurt
    • low-fat milk
  • Each volunteer:
    • Measured vaginal pH at bedtime (not soon after urination) with pH paper for two weeks, followed by:
      • two vaginal pH measurements/week for 2 weeks
      • one vaginal pH measurement/week for 2 weeks
      • a final vaginal pH measurement after 12 weeks
  • Implanted 10mL of assigned milk product into the vagina immediately after pH determination (test subjects)


  • No significant difference in vaginal pH in any of the groups
  • Reinfections
    • no milk products:  3
    • yogurt:  1
    • nonfermented acidophilus milk:  1
    • low fat milk:  0

Implications of Study:

  • Production of lactic acid by lactobacilli doesn't fully explain their beneficial role in inhibiting the growth of yeast
  • Low fat milk is as good as L. acidophilus milk/yogurt in inhibiting yeast production.  Milk products containing lactose may act by selectively stimulating indigenous or applied lactobacilli to produce lactic acid and other yeast inhibiting substances

III.  The Efficacy of Lactinex in the Prophylaxis of Amoxicillin-Induced Diarrhea (Tankanow et al)

  • Double-blinded, placebo-controlled study of 38 children (5 months-6 years) taking amoxicillin QID for 10 days
  • Test subjects (15) took Lactinex, 1 g (500 million lactobacilli/g) along with each dose of amoxicillin
  • Parent/guardian completed daily log
  • Diarrhea > 1 loose bowel movement/d throughout the study period


  • Two thirds of each group had diarrhea; therefore, no difference!
  • Incidence of diarrhea decreased during the last 4 days in the Lactinex group; incidence of diarrhea remained constant in the placebo group


Murray M:  Encyclopedia of Nutritional Supplements.  Prima Publishing, 1996.

Pradhan A, Majumdar MK:  "Metabolism of Some Drugs by Intestinal Lactobacilli and their Toxicological Considerations."  Acta Pharmacol Toxicol 58, 11-15, 1986.

Reid G, et al:  "Is there a Role for Lactobacilli in Prevention of Urogenital and Intestinal Infections?"  Clin Microbiol Rev 3, 335, 1990.

Salminen E, et al.  "Preservation of Intestinal Integrity During Radiotherapy Using Live Lactobacillus Acidophilus Cultures."  Clin Radiology 39, 435-437, 1968.

Sewester C:  The Lawrence Review of Natural Products.  St. Louis, MI:  Facts and Comparisons, 1991.

Shahani KM, Ayebo A:  "Role of Dietary Lactobacilli in Gastrointestinal Microecology."  Am J Clin Nutr 33, 2448-2457, 1980.

Shahani KM.  "Natural Antibiotic Activity of Lactobacillus Acidophilus and Lactobacillus Bulgaricus."  Cult Dair Prod J 11, 14-17, 1976.

Tankanow RM, et al.  "A Double-blind, Placebo-controlled Study of the Efficacy of Lactinex in the Prophylaxis of Amoxicillin Induced Diarrhea."  DICP Ann Pharmacother 24, 382, 1990.




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