Probiotics are healthy bacteria that we introduce into our microbiome, or digestive system, to boost the healthy bacteria that already lives there. Studies show that probiotics can benefit certain cancer patients, such as those experiencing gastrointestinal problems. However, each patient is different — therefore, probiotics are not recommended for everyone.

Probiotics can be found naturally in foods like Greek yogurt, cheese, kimchi, and pickles; they also exist in supplement and powder form. Taking probiotics can boost some of the healthy bacteria already in your gut, which works at its best when it has a balance of “good” and “bad” bacteria. A balanced gut is an important part of your body’s overall wellness.

Probiotics can be found naturally in foods like Greek yogurt.
Probiotics can be found naturally in foods like Greek yogurt.

Evidence shows that probiotics can help with long-term symptom management for cancer patients following treatment, including chemotherapy-related diarrhea. A 2014 study investigating the effects of administering probiotics to colorectal cancer survivors for 12 weeks saw a significant decrease in symptoms for patients suffering from irritable bowel symptom, ultimately improving quality of life for those patients.

Another randomized trial, conducted with 150 patients, found that patients who underwent chemotherapy and received probiotics experienced significantly less grade three and four diarrhea and also required fewer hospitalizations and dose reductions due to bowel toxicity. However, this group also had a higher number of neutropenic complications — meaning a lower-than-normal number of neutrophils, a type of white blood cell, in the blood. This can result in an infection.

In addition to alleviating  symptoms of diarrhea, probiotics can be beneficial for some patients who have preexisting health problems such as irritable bowel syndrome and those experiencing other gastrointestinal issues like constipation, gas, or bloating, according to Stacy Kennedy, MPH, RD, a senior clinical nutritionist in Nutrition Services at Dana-Farber/Brigham and Women’s Cancer Center. Kennedy also recommends that these patients regularly change the types of probiotics they consume to get the benefit of a variety of probiotic strains.

Probiotics are not the only way to maintain a healthy gut or to improve gastrointestinal problems, Kennedy says. Fiber from fruits and vegetables, nuts, and whole grain foods can maintain and improve overall gut health. Gastrointestinal issues that patients may experience, such as gas, can also be chocked up to beverages such as soda, so switching your source of hydration can be helpful.

“Probiotics can definitely be helpful and they can serve a purpose in some cases,” Kennedy says. “It’s also important to look at individual cases to look at small changes that you can make, which can have big effects.”

There are also some patients who Kennedy would not recommend probiotics to, including patients who are on clinical trials with dietary restrictions, and patients who are neutropenic. It is important to speak with a doctor or nutritionist before adding probiotics to your diet during or after cancer treatment.

How It Works

Probiotics have been shown effective against diarrhea and certain inflammatory disorders. But data from well-designed clinical trials are needed to establish their use.

Probiotics are defined by the Food and Agriculture Organization of the World Health Organization as “live microorganisms, which when consumed in adequate amounts, confer a health effect on the host”. Majority of probiotics contain bacteria that produce lactic acid, such as Lactobacillus, Streptococcus, Bifidobacterium, Propionibacterium and Enterococcus or yeasts such as Saccharomyces boulardii that are not harmful.

Probiotics have grown popular over the last two decades because they are thought to improve digestion, immune function and nutrient absorption but the most important being the reversal of dysbiosis (changes in the function or composition of gut microbes) that is thought to play a role in the development of many chronic and degenerative diseases. Although gut microbiota is known to develop at birth, nutrition, lifestyle, and changes in the host genome during later years can shift its makeup and activity, which in turn influences overall health and the risk of developing disease. Antibiotic use has also been associated with gut microbiota disruption in general population, increasing the risk of chronic disease; in patients undergoing allogeneic hematopoietic cell transplantation; as well as in allogeneic bone marrow transplantation patients. Furthermore, antibiotics were found to inhibit the benefits of immune checkpoint-inhibitors in patients with advanced cancer.Studies are underway to determine strategies for modulating the gut microbiome to improve immune response in cancer.

Probiotic supplementation is promoted for the prevention and treatment of inflammatory bowel disease, gastroenteritis, irritable bowel syndrome, allergies, dental cavities, and for the management of diarrhea due to antibiotic use, due to the bacterium Clostridium difficile, and that associated with chemotherapy.

Other methods used to change the gut microbiota include “prebiotics” and “fecal microbiota transplantation” (FMT). Prebiotics, also known as functional foods, are non-digestible food ingredients that benefit the host by selectively promoting growth or activity of helpful gut bacteria. Because probiotics are short-lived, prebiotics are sometimes added to probiotics to maintain their levels in the gut. This combination of pro- and prebiotics is called “synbiotic therapy.” FMT involves administration of fecal matter from a healthy donor into a recipient by enema, colonoscopy or through the upper gastrointestinal tract in the form of oral capsules, via nasogastric, nasoduodenal or nasoenteric tube, or by endoscopy.

Current evidence indicates that probiotics may be useful for the treatment of some inflammatory disorders, and also have anti-carcinogenic activity. But the drawbacks of the studies include small sample size and poor methodology. Well-designed trials and guidelines are needed to recommend use of probiotics. Probiotics are generally considered safe, but their long-term safety is not known. Bacteremia (presence of bacteria in the blood), fungemia (presence of fungi in the blood), and endocarditis (inflammation in the lining of the heart) have been reported following use in newborns and in immunocompromised individuals.

Purported Uses

  • Diarrhea
    Several studies have shown that probiotics are effective in treating diarrhea caused by antibiotics, due to a bacterium known as Clostridium difficile, and diarrhea due to chemotherapy.
  • Inflammatory bowel disease
    Probioitics were shown to benefit patients with pouchitis (inflammation of the ileal pouch after colectomy) and ulcerative colitis, but not those with Crohn’s disease.
  • Gastroenteritis
    There is strong evidence to support use of probiotics for controlling acute infectious diarrhea, which is the main cause of gastroenteritis.
  • Irritable bowel syndrome
    Some studies indicate a benefit, but they are not well-designed. Clinical trials with good methodology are needed.
  • Urinary tract infections
    Evidence to support use is lacking.
  • Obesity
    Probiotics were shown to have beneficial effects.
  • Diabetes
    There is evidence in favor of probiotics for individuals with diabetes.
  • Allergies
    Probiotic use had a moderate benefit in the prevention of eczema, but not other allergic conditions.
  • Dental cavities
    Probiotics were shown to increase resistance to the formation of cavities.
  • Cancer treatment-associated side effects
    Probiotic use is effective in controlling diarrhea due to chemo, in reducing infections at the site of surgery and in improving bowel function in colorectal patients.
  • Immunomodulation
    Studies done in mice show that probiotics can activate certain cells of immune system.

Do Not Take If

You are taking drugs that are substrates of hepatic drug-metabolizing enzymes: VSL3, a probiotic mixture of 8 bacterial strains, was shown to affect their activity.

Side Effects

Pediatric Case Reports:

  • Bacteremia associated with Escherichia coli and Bifidobacterium species: In pre-term infants as well as a newborn following probiotic use.
  • L. rhamnosus pneumonia: In a 11-month-old baby, secondary to a respiratory viral infection. She recovered after antibiotic therapy.
  • D-lactic acid encephalopathy, involving intermittent ataxia (inability to control volunteer muscle movement): In a 5-year-old girl following use of probiotics to control diarrhea. She was treated with oral antibiotics.
  • Bacteremia associated with Lactobacillus: In a 17-year-old boy with ulcerative colitis. His symptoms, which included fever, flushing and chills resolved following treatment with antibiotics.

Adult Case Reports:

  • Fungemia involving Saccharomyces cerevisiae: In a patient with Clostridium difficile-associated diarrhea who was treated orally with the probiotic yeast Saccharomyces boulardii.
  • Sepsis (inflammation due to an infection) associated with Saccharomyces cervesiae: In a 34-year-old woman with extensive burns, and administered Saccharomyces boulardii to improve the digestive tolerance to enteral feeding (food given through a tube into the stomach or small intestine).
  • Fungemia: In a 79-year-old woman following treatment with Sacchaflor (a probiotic consisting of S. boulardii) for Clostridium difficile-associated diarrhea. Her symptoms improved after stopping use of Sacchaflor.
  • Lactobacillus empyema (presence of pus): In a 54-year-old HIV-infected lung transplant patient, after taking a probiotic containing Lactobacillus rhamnosus GG. His symptoms resolved with antibiotic treatment.
  • Lactobacillus acidophilus bacteremia: In a patient with AIDS and Hodgkin’s disease following probiotic therapy containing L. acidophilus.
  • Sepsis due to preoperative administration of probiotics containing Lactobacillus rhamnosus: In a 24-year-old woman following an aortic valve replacement. She was treated with antibiotics.
  • Bloodstream infection: In a critically ill 64-year-old patient with acute pancreatitis (inflammation of the pancreas), following administration of a symbiotic formula containing Pediococcus pentosaceus. He was treated with antibiotics.

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