Physician's Guide to Using Probiotics in Gastrointestinal Diseases
What is a probiotic?
The World Health Organization defines probiotics as “live microorganisms, which when consumed in adequate amounts confer health and benefit to the host”. Probiotics should not be confused with prebiotics, which are non-digestible ingredients used to stimulate the growth of gut microorganisms. When a probiotic is combined with a prebiotic, it is called a symbiotic.
By definition, probiotics are alive and can colonise the digestive tract. Hence, heat-killed Bifidobacteria and Lactobacilli are not regarded as probiotics. These non-living substances may be effective when consumed but will cease to exert their effects when they are stopped.
Do probiotics work and when should it be taken for a gastrointestinal problem?
Probiotics do work. Meta-analyses have confirmed the efficacy of probiotics in various gastrointestinal diseases. These studies have also commented that the clinical trials are heterogeneous with some showing a benefit, while others showing none. The conflicting results can be explained by variations in the strain of organisms used, dosage, duration of treatment and outcomes measured. Nonetheless, probiotics are indicated in the following conditions:
How do probiotics work?
Probiotics reduce gut permeability and gut visceral sensitivity. This results in less abdominal pain, bloating and fewer difficulties with bowel movements. Probiotics also modulate the intestinal immune system by enhancing the immunological barrier and displacing pathogenic microorganisms. Gut dysbiosis is believed to be a trigger for irritable bowel syndrome (IBS). Patients with IBS have reduced gut microbiota and lower microbiota diversity as compared to healthy individuals. Gut dysbiosis alters gut permeability, gut motility, sensitivity and affects the signalling between the brain and gut. It is believed that probiotics can rectify the problem of gut dysbiosis by colonising the digestive tract.
Which bacteria have been studied?
Lactobacillus, Bifidobacterium, Streptococcus and E.coli species have been studied in numerous clinical trials. The Bifidobacterium species has been shown to improve gut transit time, stool frequency and stool consistency. The Lactobacillus species is effective in preventing antibiotic-associated diarrhoea. Both of these can reduce the symptoms of IBS and improve the eradication rate of Helicobacter pylori.
Are all probiotics equally effective?
No. There are many reasons why probiotics might differ in their efficacy. Different probiotics contain different microorganisms in different quantities and hence have different effectiveness. Microorganisms are categorised by their genus (e.g. Lactobacillus), followed by their species (e.g. acidophilus) and then their strain. Different strains of the same species can give different results. For instance, E.coli 0157:H7 is a pathogen, whereas E. coli Nissle 1917 is a probiotic. The effectiveness of an organism is both species and strain specific.
Some probiotics contain only a single strain, while others are multi-strain preparations. A meta-analysis concluded that multi-strain probiotics are more effective than single strain preparations in treating necrotising enterocolitis in infants. Multi-strain probiotics were associated with a lower mortality rate.
Another meta-analysis showed that multi-strain probiotics containing Bifidobacterium infantis improved the IBS symptoms of pain, bloating and abdominal distension, whereas Bifidobacterium infantis alone did not. However, this does not imply that all multi-strain preparations are superior. For a multi-strain probiotic to be effective, the different microorganisms should be synergistic and symbiotic, not antagonistic and competitive.
One should prescribe a probiotic which is manufactured following a stringent process. The number of microorganisms can vary unpredictably in some probiotics. One study found that several commercially available probiotics were deficient in their labelling. The microorganisms were different, under dosed, absent or the product was contaminated with bacteria.
The ideal probiotic should have an adequate amount of microorganisms. Although a high microorganism count is essential, the optimal dosage has yet to be established. The quantity of viable microorganisms within a capsule can dwindle with time. Transport, storage processes, exposure to heat and moisture can affect the viability of these microorganisms. In general, refrigeration will prolong the viability of a probiotic, especially for preparations which are not sealed. Given these factors, one can appreciate why some probiotics improve symptoms, while others do not.
Probiotics are beneficial in treating a variety of digestive disorders, and its effects are strain specific. Although the data on probiotics is promising, the ideal combination of microorganisms, duration of treatment, and quantity of microorganisms has yet to be established. To achieve the desired response to a probiotic, one can prescribe a probiotic which has been studied and validated in clinical trials.
References: 1. Goldenberg JZ, et al. Probiotics for the prevention of Clostridium difficile-associated diarrhoea in adults and children. Cochrane Database Syst Rev. 2017;12:CD006095. 2. Derwa Y, et al. Systematic review with meta-analysis: the efficacy of probiotics in inflammatory bowel disease. Aliment Pharmacol Ther. 2017;46(4):389-400. 3. Zhong C, et al. Probiotics for Preventing and Treating Small Intestinal Bacterial Overgrowth: A Meta-Analysis and Systematic Review of Current Evidence. J Clin Gastroenterol. 2017;51(4):300-311. 4. Chang HY, et al. Multiple strains probiotics appear to be the most effective probiotics in the prevention of necrotising enterocolitis and mortality: An updated meta-analysis. PLoS One. 2017 9;12(2):e0171579. 5. Yuan F, et al. Efficacy of Bifidobacterium infantis 35624 in patients with irritable bowel syndrome: a meta-analysis. Curr Med Res Opin. 2017;33(7):1191-1197. 6. Dhiman RK, et al. Probiotic VSL#3 reduces liver disease severity and hospitalization in patients with cirrhosis: a randomized, controlled trial. Gastroenterology. 2014;147(6):1327-37. 7. Zhao LN, et al. Probiotics can improve the clinical outcomes of hepatic encephalopathy: An updated meta-analysis. Clin Res Hepatol Gastroenterol. 2015;39(6):674-82. 8. Zhang MM, et al. Probiotics in Helicobacter pylori eradication therapy: a systematic review and meta-analysis. World J Gastroenterol. 2015;21(14):4345-57. 9. Saab S, et al. Probiotics are helpful in hepatic encephalopathy: a meta-analysis of randomized trials. Liver Int. 2016;36(7):986-93. 10. Jafarnejad S, et al.Probiotics Reduce the Risk of Antibiotic-Associated Diarrhea in Adults (18-64 Years) but Not the Elderly (>65 Years): A Meta-Analysis. Nutr Clin Pract. 2016;31(4):502-13. 11. Dimidi E, et al. The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2014;100(4):1075-84. 12. Wang ZH, et al. Meta-analysis of the efficacy and safety of Lactobacillus-containing and Bifidobacterium-containing probiotic compound preparation in Helicobacter pylori eradication therapy. J Clin Gastroenterol. 2013;47(1):25-32.
A Specialist’s Point of View – Written by Dr Eric Wee
Dr Eric Wee
is a Senior Consultant Gastroenterologist practicing at Nobel Gastroenterology Centre in Mount Elizabeth Novena Hospital.
Before joining the private practice, he was the Head of Gastroenterology at Khoo Teck Puat Hospital and the Associate Program Director of the NHG Gastroenterology Residency Program.
Dr Wee subspecialises in endoscopy and performs advanced procedures such as ERCP, endoscopic ultrasound and enteroscopy. His publications include review articles and book chapters on Functional dyspepsia, H.pylori, Nutrition and Endoscopy.
Dr Wee believes in collaborating with GPs and has established a direct access FibroScan, urea breath test and endoscopy (OGD/colonoscopy) service. If you have enquiries with regards to this article, you may email him at: