Drugs & MedicationsGastrointestinal DiseasesInfectious DiseasesPreventive Medicine


It’s a well-known fact that humans have bacteria in their intestinal tracts (the gut). It’s called natural flora. These bacteria help to maintain the normal functioning of the gut and are affected by changes in our diet, medicines we take (mostly antibiotics), lifestyle, and exposure to toxins. The bacteria in our gut have a working relationship with our immune system and are important for maintaining a normal equilibrium between disease and good health. Without these normal bacteria, our food doesn’t digest properly, and we are prone to diarrhea and other intestinal malfunctions. Many are listed below.

Probiotics are capsules, powder, or food supplements that are composed most often non-pathogenic bacteria which have a beneficial affect on the intestinal tracts of infants, children, and adults. They are considered a food rather than a drug. Some probiotics contain only one strain of bacteria while others are compounds composed of multiple bacterial organisms. Taking probiotic supplements introduces to the gut bacterial strains that benefit the functioning of the GI tract. The bacteria most often found in probiotics are Lactobacillus, Bifidobacterium, Escherichia, Enterococcus, Streptococcus, various other bacillary bacteria, and Saccharomyces yeast. 

Probiotics have been proven to be effective for treating a variety of intestinal problems, foremost being infantile diarrhea, necrotizing enterocolitis (bacteria infection that kills intestinal cells), antibiotic-associated diarrhea, reoccurring Clostridium Difficile colitis, Helicobacter pylori infections, inflammatory bowel disease, and on. In children, they help in treating diarrhea caused by Rotavirus. 

Exactly how probiotics work has not been explained, but it is known that restoring the bacterial count of the intestinal tract is a good thing. Stimulating the immune system strengthens the response to disease-causing bacteria, and probiotics increase one’s tolerance to lactose. 

Certain probiotics, in addition to restoring the intestinal bacterial count (number of colonies), lower intestinal pH, suppress invading pathogenic organisms, increase the number of immunoglobulins in the intestinal lining, and stimulate the release of interferons. All positive effects.

Probiotics are “live microorganisms and may themselves cause infection in the host.” There is a potential risk for septicemia or other morbidities if the dose exceeds the recommended amount. But they have a definite role in treating traveler’s diarrhea, ulcerative colitis, irritable bowel syndrome, and C. difficile infection… Studies show that “specific probiotic species or strains demonstrate specific clinical effects….[such as] for the treatment of irritable bowel syndrome and ulcerative colitis…..there is compelling news about the benefits of probiotics for the prevention and treatment of antibiotic-associated diarrhea and Clostridium difficile-associated diarrhea. 

To be effective, a probiotic should contain a dosage of 5 billion microorganisms/day of one or more types which gives the gut a greater chance to re-establish the normal bacterial count. Bloating and intestinal gas are the most frequent side effects. There is “a lack of clear guidelines on when to use probiotics and the most effective probiotic for different GI conditions.”

ACUTE INFECTIOUS DIARRHEA:  (Diarrhea caused by bacteria like Salmonella, Shigella, E. Coli) Probiotics significantly shorten the duration of diarrhea (25 fewer hours). Start probiotics at the onset of symptoms and take until one to two weeks following resolution of symptoms. Probiotics started two days before travel and throughout the trip showed a 15% decreased risk of acquiring traveler’s diarrhea. Lactobacillus reuteri reduced the duration of diarrhea in children. Lactobacillus rhamnosus probiotics helped children with the watery diarrhea from Rotavirus. 

ANTIBIOTIC-ASSOCIATED DIARRHEA, C. difficile INFECTION, and C.DIFFICILE-ASSOCIATED DIARRHEA: Started the first day of antibiotic treatment, probiotics Lactobacillus rhamnosus and Saccharomyces boulardii (5-40B colony-forming units) were effective. 

HELICOBACTER PYLORI INFECTION: Lactobacillus-containing probiotics plus antibiotics increased eradication rates.

ULCERATIVE COLITIS: Probiotics started at the onset of a flare of ulcerative colitis and taken for two weeks following resolution of symptoms significantly increased remission rates in patients with active ulcerative colitis compared to placebo. 

IRRITABLE BOWEL SYNDROME: Probiotics started at the onset of symptoms improved quality of life and significantly improved symptoms of bloating and flatulence compared to placebo. Lactobacillus plantarum and E. coli Nissle 1917 have demonstrated efficacy

CONSTIPATION: Bifidobacterium-containing yogurt eaten regularly significantly increased the number and frequency of stools, and reduced painful BM’s. 

PROBIOTICS INEFFECTIVE FOR: Acute pancreatitis, Crohn’s disease.

SUMMARY: Probiotics (or pro bios, “for life”) are most often antibiotics which are used to prevent and treat several symptomatic condition of the GI tract. Treatment is strain-specific meaning certain strains help treat certain illnesses, but not all. Probiotics are safe with very few mild side effects, but they are bacteria and excessive dosages can cause infections themselves. One reference (Wilkins, Sequoia) has an extensive list of GI conditions and the probiotic effective against each. For example, Irritable Bowel Syndrome is improved by five different probiotics and eating/taking one, or several, of them will help symptoms. The same reference contains a Table of the commercially available products that contain the probiotic you may need. Lactobacillus rhamnosus is mentioned as helpful for C. diff and is found in adequate quantity in Culturelle. 

I have taken probiotics in the past for what I thought was irritable bowel syndrome. They didn’t help, but I now know that I took the wrong probiotic. My problem, rather than irritable bowel syndrome, was probably intolerance to high fructose corn syrup. Avoiding foods that contain HFCS has begun to improve the situation. 

Before you go buy a probiotic just “Willy, nilly,” investigate your problem and determine the best probiotic and the correct dose so you won’t be wasting time and money. There should be many reference sources to check before deciding. 

References: Gupta V, Garg R. Probiotics Indian J Med Microbiol 2009 Jil-Sep;27(3):202-209.

Williams NT. Probiotics Am J Health System Pharm 2010 Mar 15;67(6):440-458.

Sue’s J, Zmora N, Segal E, Elinav E. The pros, cons, and many unknowns of probiotics. Nat Med 2019 May;25(5):716-729.

Hana way PJ Which Probiotics Should I Take? A Practical Guide for Family Physicians Am Fam Phys 2017 August 1;96(3):?

Wilkins T, Sequoia J, Probiotics for Gastrointestinal Conditions: A Summary of Evidence Am Fam Phys 2017 August 1;96(3):170-178. 

Sarowska J, Chorosy-Krol I, Regulske-Ilow B, Frej-Madrzak M, Jama-Kmiecik A. The therapeutic Effect of Probiotic z bacteria on Gastrointestinal Diseases Adv Clin Exp Med 2013 ;22(5):759-766.

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    1. Yes, with antibiotics and anti fungals. In healthy people they are harmless. In immunocompromised patients they can cause sepsis and death. Acidic foods and citrus fruit interact adversely with probiotics, too. Anything in moderation is safer, but overdoing it with them can be harmful.

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