Probiotics are live microorganisms (usually bacteria or yeasts) that when taken orally may be able to help prevent or treat some illnesses. They can be in capsule form or occur in certain foods such as yoghurt and fermented foods. There are however many questions surrounding their use. Which organisms should be used? When should they be taken? How long should they be taken for? Do they have any side effects? Do they actually work?

One of the most common reasons to take a probiotic is to counteract some of the effects of an antibiotic. Our gut is full of bacteria and other organisms that are an essential part of us; without them we would be sick indeed. These organisms work with us in various ways. They help us digest food, metabolise drugs, prevent some gut infections, detoxify toxins, produce vitamins and help maintain homeostasis in the gut.

When we take an antibiotic we kill off some of our good gut bugs and change the internal milieu. This can lead to problems, one of which is antibiotic associated diarrhoea.

Does taking a probiotic with a course of antibiotics help prevent this? A metanalysis of 25 randomised controlled trials by McFarland in 2006 demonstrated that probiotics caused a significant reduction in antibiotic associated diarrhea. The best types to take included Lactobacillus rhamnosus GG and Saccharomyces boulardii. Probiotics do help to prevent antibiotic associated diarrhoea; they should be taken during and after the course of antibiotics, between doses and with food.

Another popular use for probiotics is to prevent acute diarrhoea or traveller’s diarrhoea. Here there are some studies demonstrating benefit. One by de Vrese in 2007 demonstrated a decrease in frequency of infections and a decrease in duration of illness. Various different probiotic strains showed benefit.

Probiotics have also been used to treat irritable bowel syndrome (IBS). A review by McFarland in 2008 demonstrated improved symptoms and decreased abdominal pain.

There are many other proposed uses for probiotics – to help with acute diarrhoeal illness, to help treat inflammatory bowel disease, to help with eczema and other allergic diseases, in people with recurrent infections, to improve immunity, to help treat chronic fatigue. The list is endless and will require a great deal of research to determine if probiotics help and which ones help for which condition. They are not a panacea and one size does not fit all.


McFarland LV. Meta-analysis of probiotics for the prevention of antibiotic associated diarrhea and the treatment of Clostridium difficile disease. Am J Gastroenterol, 2006 101: 812-22

De Vrese M, Marteau PR. Probiotics and prebiotics: effects on diarrhea. J Nutr 2007 Suppl 803S-11S.

McFarland LV, Dublin S. Meta-analysis of probiotics for the treatment of irritable bowel syndrome. World J Gastroenterol. 2008; 14: 2650–2661.