Probiotics are a hot topic in nutrition and health. They are popularly thought to have great potential in improving gut health, reducing risk of some diseases, or balancing the body’s response to some medications. But what are they, really? 

According to the FAO and WHO, probiotics are “live microorganisms which when administered in adequate amounts confer a health benefit on the host” (1). In other words, probiotics are specific bacteria that have the potential to offer beneficial effects to those who take them as a supplement, food ingredient, or medication. Though the word “bacteria” often has negative associations, our bodies (and digestive tracts in particular) are full of various types of bacteria that have been shown to be important for health. Probiotics are one example of this – some of these bacterial strains have been shown to have specific beneficial effects and generally carry low risk (2). 

Probiotics are sold as supplements or medications to be taken in pill, liquid or powder form, as beauty or skin products to be applied, or as natural components or supplemented ingredients in food products. Yogurt, kefir, kombucha, sauerkraut, kimchi, pickled vegetables and miso are some examples of food products that are naturally high in probiotics due to their fermentation processing. Though some foods and supplements are labelled as containing probiotics, they haven’t necessarily demonstrated proven health benefits. 

Current Probiotic Recommendations

Probiotics may be recommended to individuals to improve digestion, to decrease risk of unpleasant gastrointestinal symptoms, to minimize the negative microbiome effects of antibiotics or other medications, to improve skin clarity, to enhance immunity and more. However, there are currently only a few evidence-based reasons to take supplemental probiotics. For example, two probiotic strains (Lactobacillus rhamnosus GG and Saccharomyces boulardii) are a recommended part of the therapy for treating acute infectious diarrhea in pediatric patients (3). Antibiotics are often associated with diarrhea due to disrupting the delicate microbiome balance; research supports probiotics (Lactobacillus rhamnosus GG and Saccharomyces boulardii) for adults starting within 2 days of antibiotic therapy to prevent this unpleasant side effect (4).

On the other hand, while there is some evidence that probiotics can be beneficial to reduce symptoms of Irritable Bowel Syndrome, though there is not enough research to support recommending certain types, doses, and durations of probiotic treatment in this case (5). High total and LDL cholesterol have been improved in some probiotic trials using mixed or specific strain supplements, though further research is needed to confirm these findings (6).  

Probiotics as a therapeutic strategy for obesity is currently a prominent area of research. Studies have clearly shown obese individuals have distinct changes in their microbiome compared to individuals with normal weight (7). However, probiotic trials have been mixed in obese populations. While some studies show increased weight loss with probiotics, others show little to no effect (8, 9, 10). Given the microbiome changes in obesity, this is a very interesting and promising area for further research. 

Who Should Use Probiotics?

While it is important to note that while probiotics are largely and generally considered to be safe, there have been reports of some minor side effects such as unpleasant gastrointestinal symptoms. Individuals who are immunocompromised or otherwise at high risk should keep probiotic use to only the strains and indications that have been shown to be safe and to have clearly beneficial associations (11).  

In conclusion, it is important to note that the health benefits related to probiotics are dependent on the bacterial species and strains, so the specific effects of each probiotic must be properly studied. Recommendations for the use of probiotics should be extremely specific, as different species may confer different effects (5). We also know that each of us has a unique microbiome makeup. Ongoing research in personalized nutrition and the individual response to targeted probiotic therapies will continue to elucidate mechanisms by which we can improve weight loss and optimize health. 

Sources:

1. Joint FAO/WHO Working Group Report on Drafting Guidelines for the Evaluation of Probiotics in Food London, Ontario, Canada, April 30 and May 1, 2002. 

2. Probiotics: What You Need to Know. https://www.nccih.nih.gov/health/probiotics-what-you-need-to-know. Updated August 2019. Accessed October 14, 2020. 

3. Szajewska H, Guarino A, Hojsak I, Indrio F, Kolacek S, Shamir R, Vandenplas Y, Weizman Z; European Society for Pediatric Gastroenterology, Hepatology, and Nutrition. Use of probiotics for management of acute gastroenteritis: a position paper by the ESPGHAN Working Group for Probiotics and Prebiotics. J Pediatr Gastroenterol Nutr. 2014 Apr;58(4):531-9. doi: 10.1097/MPG.0000000000000320. Erratum in: J Pediatr Gastroenterol Nutr. 2016 Jan;62(1):188.  

4. Szajewska H, Kołodziej M. Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Aliment Pharmacol Ther. 2015 Oct;42(7):793-801. doi: 10.1111/apt.13344. Epub 2015 Jul 27. 

5. Probiotics. https://ods.od.nih.gov/factsheets/Probiotics-HealthProfessional/. Updated June 3, 2020. Accessed October 14, 2020. 

6. Shimizu M, Hashiguchi M, Shiga T, Tamura HO, Mochizuki M. Meta-Analysis: Effects of Probiotic Supplementation on Lipid Profiles in Normal to Mildly Hypercholesterolemic Individuals. PLoS One. 2015 Oct 16;10(10):e0139795. doi: 10.1371/journal.pone.0139795. 

7. Turnbaugh PJ, Ley RE, Mahowald MA, Magrini V, Mardis ER, Gordon JI. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature. 2006 Dec 21;444(7122):1027-31. doi: 10.1038/nature05414.  

8. Crovesy L, Ostrowski M, Ferreira DMTP, Rosado EL, Soares-Mota M. Effect of Lactobacillus on body weight and body fat in overweight subjects: a systematic review of randomized controlled clinical trials. Int J Obes (Lond). 2017 Nov;41(11):1607-1614. doi: 10.1038/ijo.2017.161. Epub 2017 Jul 10. 

9. Suzumura EA, Bersch-Ferreira ÂC, Torreglosa CR, da Silva JT, Coqueiro AY, Kuntz MGF, Chrispim PP, Weber B, Cavalcanti AB. Effects of oral supplementation with probiotics or synbiotics in overweight and obese adults: a systematic review and meta-analyses of randomized trials. Nutr Rev. 2019 Jun 1;77(6):430-450. doi: 10.1093/nutrit/nuz001.  

10. Dror T, Dickstein Y, Dubourg G, Paul M. Microbiota manipulation for weight change. Microb Pathog. 2017 May;106:146-161. doi: 10.1016/j.micpath.2016.01.002. Epub 2016 Jan 12. 

11. World Gastroenterology Organisation. WGO Global Guideline: Probiotics and prebiotics. https://www.worldgastroenterology.org/UserFiles/file/guidelines/probiotics-and-prebiotics-english-2017.pdf. Updated 2017. Accessed October 15, 2020.