Research News

Probiotics have no effect on gut microbiota in healthy people, review suggests

BMJ 2016; 353 doi: (Published 10 May 2016) Cite this as: BMJ 2016;353:i2617
  1. Susan Mayor
  1. London

Probiotics have no consistent effect on the gut microbiota in healthy people, a systematic review has shown.1

Molecular sequencing techniques have enabled detailed identification of the diversity and functional capacity of micro-organisms in the gut, leading to claims that a wide range of conditions, including colorectal cancer and type 2 diabetes, may be associated with disease specific changes in gut microbiota.

Studies have shown that probiotic supplements containing live bacteria may be beneficial in specific diseases, but these products are also marketed to healthy people who show little evidence of benefit.

Researchers carried out a systematic review of peer reviewed papers reporting on randomised controlled trials that compared placebo with the effects of probiotic supplementation on faecal microbiota assessed by genetic sequencing in healthy adults.

They analysed seven randomised trials in the review, each including 21-81 participants. The probiotics tested contained Lactobacillus, Bifidobacterium, and Lactobacillus combined or Bacillus provided in milk based drinks, sachets, capsules, or biscuits, at doses of about 109 to 1011 colony forming units for 21-42 days.

Results showed no effects on faecal microbiota in terms of the diversity or richness of the microbiota with probiotics when compared with placebo. Only one study found that probiotic supplementation significantly modified the overall structure and diversity of the faecal bacteria community.

“While there is some evidence from previous reviews that probiotic interventions may benefit those with disease associated imbalances of the gut microbiota, there is little evidence of an effect in healthy individuals,” said the research group, led by Oluf Pedersen, of the University of Copenhagen, Denmark. They concluded that much larger, carefully designed clinical trials of probiotics are needed to explore their role on disease prevention in healthy people.


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