Probiotics - Are they really helpful?

Dr John P Wright

Updated: 2022

There is another article on this website called "Leeches and Probiotics". This article looks a little more specifically at the data that has been published in the last six years. The data is no more supportive now than it was then. The belief and faith in probiotics, however, continues unbounded. To cast doubt on probiotics is a bit like Galileo saying that the world revolves around the sun and not vice versa. This belief led to his arrest and sentence on 22 June 1633 to house arrest with the added indignity that he had to recite the seven penitential psalms once a week. He died nine years and 416 recitals later. It is not recorded whether this changed the science. It was in 1984, 350 years later, that the concept of the earth rotating around the sun was accepted.

In the face of the international groundswell of support for probiotics, it is difficult to find the truth. When studies find little support for their use, words such as useful and beneficial tend to predominate.

The Cochrane collaboration is probably the best source of objective evidence as it pertains to the use of probiotics.

The gastrointestinal areas most commonly treated with probiotics remain irritable bowel, Infective diarrhoea, inflammatory bowel disease, pouchitis and for preventing allergies in children. More recently, the use of probiotics to boost the immune system, reduce allergies and avoid cancer has been promoted. These can very quickly be disposed of as there is currently no evidence to support these attributes.

The more common gastrointestinal indications are:

1. Treating acute infectious diarrhoea.

The Cochrane Reviews in 2010 reported that in 35 studies with 4555 patients, the average reduction in duration of diarrhoea was 24 hours and the diarrhoea lasted less than four or more days. This only applies to diarrhoea caused by bacterial infection. This is less common than viral-induced.

Another review in 2019 showed that in children, there might be a slight reduction in antibiotic-associated diarrhoea. To benefit one child, one would need to treat six others with no benefit. Hardly cost-effective.

2. Preventing Clostridium difficle colitis

Clostridium difficle is a bacterium that can live in our gastrointestinal tracts and cause no problem until the environment changes through illness, surgery, antibiotic usage or superinfection with a virulent strain. It can then cause a serious illness with severe diarrhoea.

A Cochrane Review in 2013 concluded that the use of probiotics had a statistically significant reduction in the incidence of Clostridium difficle associated diarrhoea in patients on antibiotics. The incidence in the probiotic group was 2.0% compared to 5.5% in the placebo or no treatment control group suggesting that 29 patients would need to be treated to prevent one case of Clostridium difficle associated diarrhoea. Importantly, however, when they compared the rate of actual infection with Clostridium difficle, there was no difference between the treatment groups. The reason for this is probably related to the sensitivity of the PCR method used, which picks up the mere presence of the genetic material of Clostridium difficle, which may be found in apparently healthy individuals.

3. Treatment of Clostridium difficile colitis

A Cochrane Review in 2008 stated that there is insufficient evidence to recommend probiotic therapy as an adjunct to antibiotic therapy for C. difficile colitis. There is no evidence to support the use of probiotics alone in the treatment of C. difficile colitis.

4. Treating Crohn’s Disease and ulcerative disease

In 2006 a Cochrane Review found no evidence to suggest that probiotics are beneficial for the maintenance of remission in Crohn's Disease.

In 2015 they reported that remission of ulcerative colitis could not be induced by probiotics.

5. Treating of acute or chronic pouchitis

A pouch is made of small bowel in the pelvis when the colon is removed. It has a problem of becoming inflamed at some time after surgical creation.

This was the one area where probiotics were thought to have value, but in 2015 it was reported that for chronic pouchitis, low-quality evidence suggests that a specific probiotic, VSL#3, may be more effective than placebo for maintenance of remission. Similarly, for the prevention of pouchitis, low-quality evidence suggests that VSL#3 may be more effective than placebo.

6. Using probiotics in patients with irritable bowel syndrome

This is probably the most vexatious indication as irritable bowel syndrome is so widespread and the symptoms experienced so varied.

A review article in World J Gastroenterol. in 2013 stated that there is reasonable evidence of a modest benefit in IBS patients. Selection of those who will respond requires a better understanding of exactly what the mode of action is in IBS. Like most therapies in IBS, probiotics are unlikely to be beneficial for all patients.”

In summary, the objective data suggests that some probiotics may be “helpful” in some conditions. The clinical gains are small and may lead to a false sense of security. In this context, it is important to understand the difference between statistical and clinical significance. If an intervention reduces the incidence of disease from, say, 60% of a population to 58%, this may have no clinical significance when considering the cost or side effects of the intervention and yet be highly statistically significant. Statistical significance just means that the result is likely to be true but not necessarily clinically useful.

It is often stated that if probiotics do no harm and may help, why not use them. This is the same justification for using placebos which reduces the adult patient to the level of a child and is inherently dishonest. At some stage, probiotics may well come of age, but meanwhile, we do not know what we are doing with them.

In conclusion, if we wish to avoid the blind arrogance that led to Galileo’s internment and dismissal for 350 years, we need to adhere to the scientific basis of our profession and re-dedicate ourselves to evidence-based medicine.

- Dr John P Wright