What the Evidence Says About Probiotics and Health

July 16, 2018

By Jyothirmai Gubili, MS, K. Simon Yeung, Pharm D, Lac, and Eugenie Spiguel, MSN, ANP-BC

Consumption of probiotics—live microorganisms—can offer health benefits by reversing dysbiosis: changes in the composition or function of gut microbes associated with the development of many chronic and degenerative diseases. Most probiotics are nonvirulent, lactic acid–producing bacteria, including Lactobacillus, Streptococcus, Bifidobacterium, Propionibacterium, and Enterococcus, or yeasts such as Saccharomyces. They are available as dietary supplements or can be obtained from yogurt and other fermented foods. Probiotics have grown in popularity over the past few decades because of perceived benefits such as improved digestion, immune function, and nutrient absorption.  

Scientific Evidence

Randomized controlled trials have reported orally administered probiotics to be useful in controlling acute infectious diarrhea (https://www.ncbi.nlm.nih.gov/pubmed/16728323), antibiotic-associated diarrhea (http://www.ncbi.nlm.nih.gov/pubmed/22570464), and recurrent abdominal pain in children (https://www.ncbi.nlm.nih.gov/pubmed/28334433). Probiotics were also found useful for treating and sustaining remissions of mild to moderately active ulcerative colitis (https://www.ncbi.nlm.nih.gov/pubmed/26598094) and offered moderate benefit against eczema in infants (https://www.ncbi.nlm.nih.gov/pubmed/26044853).

A systematic review showed a reduction in the severity and frequency of treatment-associated diarrhea (http://www.ncbi.nlm.nih.gov/pubmed/24618152), and the need for antidiarrheal medication, following probiotic supplementation in patients with cancer. Additional studies in patients with colorectal cancer indicated that perioperative treatment with probiotics helped lower surgical site infections (http://www.ncbi.nlm.nih.gov/pubmed/26622423) in patients undergoing surgery and improved bowel function (http://www.ncbi.nlm.nih.gov/pubmed/26824990).

Other approaches to modify gut microbiota include the use of prebiotics and fecal microbiota transplantation (FMT). Prebiotics, such as fructans and inulin, are nondigestible foods that selectively facilitate growth or the activity of useful gut bacteria. Because probiotics are short-lived, prebiotics can be coadministered to maintain their levels in the gut. The combination is known as symbiotic therapy and has been reported useful in managing irritable bowel syndrome (http://www.ncbi.nlm.nih.gov/pubmed/26900286). FMT involves administration of fecal matter from a healthy donor into a recipient. Current evidence (https://www.ncbi.nlm.nih.gov/pubmed/27214585) to support its use (https://www.ncbi.nlm.nih.gov/pubmed/28195066) for Clostridium difficile infection, a common problem in hematopoietic stem cell transplant recipients, is encouraging.

Proposed mechanisms underlying the actions of probiotics include production of compounds that inhibit the growth of pathogenic microorganisms as well as substrates to facilitate growth of beneficial bacteria. They may also indirectly influence changes in microbiota (https://www.ncbi.nlm.nih.gov/pubmed/21992949) through their interactions with the mucosal system, affecting systemic immunity, as well as by decreasing proinflammatory markers (http://www.ncbi.nlm.nih.gov/pubmed/26548336) associated with many disorders.

Probiotics are generally considered safe and side effects are rare, but bacteremia (http://www.ncbi.nlm.nih.gov/pubmed/23426446) and fungemia (http://www.ncbi.nlm.nih.gov/pubmed/24674691) have been reported following use in newborn babies, immunocompromised adults, and  individuals with diarrhea.

What Oncology Nurses Need to Know

Accumulating evidence suggests that probiotics can have a positive impact on health by inducing favorable changes in gut bacteria. But data are not robust because of small sample sizes, poor methodology, variations in bacteria species and strains, dosages, and administration duration. Larger, well-designed trials are needed to establish recommendations for probiotic use.

As a trusted member of the healthcare team, oncology nurses are often the first to discuss patients’ supplement and vitamin use, thereby providing a distinctive opportunity to specifically address patient questions and concerns. Patients may be surprised to learn that their over-the-counter supplements may interfere with their treatment or be potentially harmful. Oncology nurses should counsel patients about the possible risks of probiotics, particularly for patients who are immunocompromised, and can facilitate discussion among the healthcare team about probiotic use to determine when it may be appropriate and when it may be detrimental.

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