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Are Probiotics Really Useless?

Are Probiotics Really Useless?
By Clinical Nutrition 2 months ago 12783 Views

In a rather surprising news story, some scientists in Israel have labelled most probiotics as ‘useless’, based on their recent research.Unfortunately it’s a hollow conclusion that doesn’t stand up to scrutiny and flies in the face of much long-standing good quality evidence. Probiotics are not useless, of course. It really depends which ones, how potent they are, and what you are expecting them to do.

In fact, the right probiotics have been shown to positively change the balance of gut bacteria when it gets out of balance, and to improve a wide range of symptoms such as antibiotic associated diarrhoea. Far from useless, many people understand the clear benefits they get from taking them every day.

The Israel study gave one particular combination of probiotics to 15 people for a month and looked at whether the bacteria populated the gut permanently, but...

  • It’s just one particular blend of probiotics. There are many different types of probiotics available that you can take of different strengths, type of bacteria and quality. To take just one and apply the conclusions to all probiotics is like studying potatoes and then saying your findings apply to all vegetables.
  • They didn’t look at ‘usefulness’ - Useless implies they measured whether the probiotics did anything functionally useful. They didn’t look at that. They didn’t look at motility, integrity or any other key gut function.
  • It’s only 15 people and they only gave the volunteers a 5 billion 11 strain probiotic product twice daily for 4 weeks - nowhere near the sample size, dose, or duration with which to properly assess the ability of probiotics to colonise the gut. There are multiple probiotic studies with positive results that have been conducted on tens of thousands of people over the years.
  • They didn’t look at imbalanced guts in the first place - Their measure was that there wasn’t significant or permanent change to the composition of gut bacteria in half of the subjects. But they didn’t give the bacteria to people who had imbalanced guts to start with (see the other study where some of the same scientists did and it was a different story).
  • Is restoring gut balance the whole story anyway? Essentially the authors assume the only way probiotics can be useful is if they populate and change the gut bacterial balance permanently. But this simply isn’t true. In fact, probiotics exert some effects called ‘transient effects’ by stimulating the immune system as they pass through and by secreting useful substances that support overall gut health. The authors even concluded that the supplement changed these chemicals produced in the gut. This is not a useless effect. So, as we already know, it may be more what probiotics do, rather than where they are that results in the benefits people experience.
  • Also there were temporary changes to the composition of bacteria in the other half of subjects in this study. This tendency to revert back to the original balance of bacteria they observed is perfectly consistent with other findings on probiotics and does not negate the positive effects. It’s like saying taking aspirin is pointless because it doesn’t do anything after you stop taking it. And anyway, as it happens, there are other studies with other types and combination of probiotics that show a clear positive effect on gut bacteria balance from giving probiotics, especially after it has been disrupted, by antibiotics, for example.
  • Probiotics have consistently shown useful benefits in many other studies - Many studies show positive effects of probiotics on antibiotic associated diarrhoea, IBS, constipation, enhancing immunity, preventing allergy and a whole host of really important stuff.[i]
  • Good for Antibiotics or not? In another related study, Zmora presents a negative view on the role probiotics play in ameliorating the effects of antibiotics.[ii] They note that the 11 strain probiotic given seems to prevent the gut balance of bacteria returning to its ‘normal state’ for longer. They felt this might be a problem, but in fact all it tells us is that the probiotics did produce a significant change in this case in people with disrupted gut bacteria. The assumption here is that the goal is to revert the gut back to its original state to have a positive functional effect when antibiotics disrupts its status. But perhaps the positive effect shown in so many studies arises from a more fundamental temporary change and that this is protective, not negative. The study noted that probiotic supplementation, and in particular the Lactobacillus strains, increased the production of anti-microbial chemicals, which had an inhibitory effect on the growth of Clostridium and Prevotella species. Although not specifically assessed in this study, we know that certain probiotics can have a positive impact on reducing the incidence and virulence[i],[ii] of Clostridium difficile, which is a potentially fatal form of bacterial infection, associated with antibiotic use and antibiotic resistance.
  • In fact, the best data on probiotics for antibiotic use comes from several robust meta-analyses showing clear benefits for diarrhoea reduction, including this one.[iii]Whatever effect those probiotics are having on the bacterial composition of the gut, it’s certainly not a useless one.
  • And, of course, again, these results only apply to this particular blend of probiotics for this very small number (21) of subjects. Other more potent and effective probiotics might demonstrate different effects. The scope of this study is so breathtakingly narrow, it should be hard to draw any firm, or sweeping, conclusions.
  • There were some positives of course. This study used sampling of bacteria directly from people’s guts rather than stool sampling, and so is more accurate. They demonstrated clear changes from taking probiotics in both groups. They just weren’t the changes they were expecting. So the studies give us some useful information on how exactly probiotics do work (and don’t) and what our clinical measures should really be.

The simple fact is that if you use the right bacteria – well-characterised, robust, safe, stable and in the right quantities, you can exert positive effects on gut health and this has been demonstrated in many other studies.

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[i] Valdes. Role of the gut microbiota in nutrition and healthBMJ 2018;361:k2179

[ii] Suez. Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. CellVOLUME 174, ISSUE 6, P1406-1423.E16, SEPTEMBER 06, 2018.

[i] Johnson et al. Is primary prevention of Clostridium difficile infection possible with specific probiotics? Int J Infect Dis. 2012 Nov;16(11):e786-92.

[ii] Plummer et al. Clostridium difficile pilot study: effects of probiotic supplementation on the incidence of C. difficile diarrhoea. Int Microbiol. 2004 Mar;7(1):59-62.

[iii] Blaabjerg S, Artzi DM, Aabenhus R. Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Outpatients-A Systematic Review and Meta-Analysis. Antibiotics (Basel). 2017 Oct 12;6(4).

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