Other common name(s): lactic acid bacteria
Scientific/medical name(s): Lactobacillus acidophilus (L. acidophilus)
Acidophilus is a type of germ or bacterium commonly found in the normal digestive tract of mammals, mainly in the small intestine. It is also found in many dairy products, especially yogurt. Acidophilus and some related bacteria are considered to be "probiotic" because they may help the body maintain or restore its normal balance of helpful bacteria.
Acidophilus has been promoted for a wide variety of conditions, including cancer. Animal studies looking at the role of L. acidophilus in reducing the risk of cancer have shown varying results. There have been no studies with humans on the role of Lactobacillus acidophilus in preventing or treating human cancers.
How is it promoted for use?
Acidophilus is often promoted as a supplement to help “maintain bowel health.” It has also been suggested to prevent or treat diarrhea and vaginal infections, to lower cholesterol, to help with lactose digestion in lactose-sensitive people, and to help prevent the growth of the types of bacteria and yeast that can cause illness.
Some supporters claim acidophilus may lower the risk of cancer, especially colon cancer. It is supposed to do this by neutralizing cancer-causing agents (carcinogens) in the diet and by directly killing tumor cells. Some also claim that acidophilus works against cancer by boosting the immune system by making B vitamins and vitamin K, and that it reduces cholesterol levels, which proponents say tumor cells need in order to grow.
What does it involve?
When taking acidophilus, the dosage usually refers to the number of live bacteria. Most sources suggest 1 to 15 billion bacteria as a recommended dose, although some studies have used larger amounts. It’s available in tablet, capsule, liquid, and powder form. Average dosage suggestions vary from 1 to 3 times per day. However, some scientists warn that the concentration of the bacteria in the supplements varies widely from one manufacturer to another. Yogurt with live cultures and milk with L. acidophilus added to it are other sources. Some women treat vaginal problems by taking acidophilus, either by mouth or by putting liquids containing acidophilus into the vagina. A few recommend inserting whole tablets into the vagina, even those that are not designed for use in the vagina.
What is the history behind it?
Interest in the health benefits of acidophilus began in the late 1800s when it was proposed that the long life span of the Balkan people was due to their ingestion of fermented milk products. It was later found that these milk products were rich in L. acidophilus. Since then, the exact role of L. acidophilus in the digestive tract and in human health has been a subject of interest.
What is the evidence?
Laboratory and animal studies on the ability of L. acidophilus to prevent cancer have had mixed results, and there have been no large studies reported in humans. L. acidophilus has been studied in the laboratory for possible anti-tumor properties. In some studies, milk that was fermented by L. acidophilus was able to slow or prevent the growth of breast and colon cancer cells grown in the laboratory.
In other studies, animals that were given L. acidophilus were found to be less prone to DNA damage in the colon after being given known carcinogens, suggesting acidophilus might have an effect on colon cancer. However, animal studies have shown that diets that include L. acidophilus do not seem to affect the formation of breast or skin cancers. In either case, randomized studies in people have not been done. Further studies are needed to determine whether the results apply to humans.
Researchers have also studied the effects of L. acidophilus and other probiotics on certain reproductive hormones known in high levels to increase risk of breast cancer. In studies of both pre- and post-menopausal women, L. acidophilus had no effect.
A Japanese study looked at the effect of a related bacterium (Lactobacillus casei) on the risk of colon tumors in about four hundred men and women who had previous tumors removed. The risk of new tumor development was not significantly lower in those who took L. casei, although the tumors that did develop contained cells that were less abnormal.
A review of research on the effects of acidophilus and other closely related bacteria found that they lowered cholesterol in early studies, but later, better-controlled studies have not been consistent in showing this effect. It also found that a related bacterium (Lactobacillus GG) may shorten the duration of diarrhea due to viral or bacterial infections.
A 2010 Chinese study looking at hospitalized patients gave them doses of 50 billion, 100 billion bacteria (L. acidophilus plus L. casei), or placebo each day during antibiotic treatment and for 5 days after. The researchers reported that both Lactobacillus groups had less diarrhea from taking antibiotics than the placebo group, and the higher dose seemed to work better.
Finally, a 2012 analysis of 63 human studies looking at probiotic bacteria found that taking them reduced the risk of diarrhea from taking antibiotics. This review included studies of a number of different types of bacteria, although most used Lactobacillus species.
A few recent studies suggest that acidophilus or related Lactobacillus species may reduce the severity of diarrhea occurring with chemotherapy for colorectal cancer or with radiation therapy for colorectal or cervical cancer.
Are there any possible problems or complications?
There appear to be few short-term problems with taking acidophilus. Some people have reported excess bloating or gas for the first few days while taking the supplement. In rare cases, acidophilus may cause serious infections that are hard to treat with antibiotics. People with weakened immune systems, such as those who are taking steroids or undergoing chemotherapy, who have received organ transplants, or who have AIDS, should use acidophilus and other probiotics with caution.
The lack of standardization makes it hard to be sure of the quality of acidophilus and other probiotic products. Because acidophilus must contain live cultures in order to be effective, proper packaging and storage is essential. Many products may contain other bacteria or may not contain enough of the active organisms, especially if the product has been sitting on a shelf for a while.
Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.
To learn more
More information from your American Cancer Society
The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).
The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management
Baricault L, Denariaz G, Houri JJ, Bouley C, Sapin C, Trugnan G. Use of HT-29, a cultured human colon cancer cell line, to study the effect of fermented milks on colon cancer cell growth and differentiation. Carcinogenesis. 1995;16:245-252.
Biffi A, Coradini D, Larsen R, Riva L, Di Fronzo G. Antiproliferative effect of fermented milk on the growth of a human breast cancer cell line. Nutr Cancer. 1997;28:93-99.
Bolognani F, Rumney CJ, Pool-Zobel BL, Rowland IR. Effect of lactobacilli, bifidobacteria and inulin on the formation of aberrant crypt foci in rats. Eur J Nutr. 2001;40:293-300.
Bonorden MJ, Greany KA, Wangen KE. et al. Consumption of Lactobacillus acidophilus and Bifidobacterium longum do not alter urinary equol excretion and plasma reproductive hormones in premenopausal women. European Journal of Clinical Nutrition. 2004;58:1635-1642.
Chitapanarux I, Chitapanarux T, Traisathit P, et al. Randomized controlled trial of live lactobacillus acidophilus plus bifidobacterium bifidum in prophylaxis of diarrhea during radiotherapy in cervical cancer patients. Radiat Oncol. 2010 May 5;5:31.
Delia P, Sansotta G, Donato V, FrosinaP, Messina G, De Renzis C, Famularo G. Use of probiotics for prevention of radiation-induced diarrhea. World J Gastroenterol. 2007;13:912-915.
de Roos NM, Katan MB. Effects of probiotic bacteria on diarrhea, lipid metabolism, and carcinogenesis: a review of papers published between 1988 and 1998. Am J Clin Nutr. 2000;71:405-411.
Gao XW, Mubasher M, Fang CY, et al. Dose-response efficacy of a proprietary probiotic formula of Lactobacillus acidophilus CL1285 and Lactobacillus casei LBC80R for antibiotic-associated diarrhea and Clostridium difficile-associated diarrhea prophylaxis in adult patients. Am J Gastroenterol. 2010 Jul;105(7):1636-1641.
Ishikawa H, Akedo I, Otani T, et al. Randomized trial of dietary fiber and Lactobacillus casei administration for prevention of colorectal tumors. Int J Cancer. 2005;116:762-767.
Hempel S, Newberry SJ, Maher AR, et al. Probiotics for the prevention and treatment of antibiotic-associated diarrhea: a systematic review and meta-analysis. JAMA. 2012 May 9;307(18):1959-1969.
Hove H, Norgaard H, Mortensen PB. Lactic acid bacteria and the human gastrointestinal tract. Eur J Clin Nut. 1999;53:339-350.
Jones ML, Martoni CJ, Parent M, Prakash S. Cholesterol-lowering efficacy of a microencapsulated bile salt hydrolase-active Lactobacillus reuteri NCIMB 30242 yoghurt formulation in hypercholesterolaemic adults. Br J Nutr. 2012 May;107(10):1505-1513.
M. D. Anderson Cancer Center. Lactobacillus acidophilus. Accessed at: www.mdanderson.org/departments/cimer/display.cfm?id=28A0EE0D-11E2-4060-B5CEE2CE90A7295B&method=displayFull&pn=6EB86A59-EBD9-11D4-810100508B603A14 on June 10, 2008. Content no longer available
Moroti C, Souza Magri LF, de Rezende Costa M, et al. Effect of the consumption of a new symbiotic shake on glycemia and cholesterol levels in elderly people with type 2 diabetes mellitus. Lipids Health Dis. 2012 Feb 22;11:29.
Nettleton JA, Greany KA, Thomas W, Wangen KE, Adlercreutz H, Kurzer MS. Short-term soy and probiotic supplementation does not markedly affect concentrations of reproductive hormones in postmenopausal women with and without histories of breast cancer. Journal of Alternative & Complementary Medicine. 2005;11:1067-1074.
Osterlund P, Ruotsalainen T, Korpela R, Saxelin M, Ollus A, Valta P, Kouri M, Elomaa I, Joensuu H. Lactobacillus supplementation for diarrhoea related to chemotherapy of colorectal cancer: a randomised study. Br J Cancer. 2007;97:1028-1034.
Pool-Zobel BL, Neudecker C, Domizlaff I, et al. Lactobacillus-and bifidobacterium-mediated antigenotoxicity in the colon of rats. Nutr Cancer. 1996;26:365-380.
Rao CV, Sanders ME, Indranie C, Simi B, Reddy BS. Prevention of colonic preneoplastic lesions by the probiotic Lactobacillus acidophilus NCFMTM in F344 rats. Int J Oncol. 1999;14:939-944.
Rice LJ, Chai YJ, Conti CJ, Willis RA, Locniskar MF. The effect of dietary fermented milk products and lactic acid bacteria on the initiation and promotion stages of mammary carcinogenesis. Nutr Cancer. 1995;24:99-109.
Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.
Last Revised: 01/15/2013