Probiotics increase stool frequency in adults suffering from constipation – meta-analysis

By Tingmin Koe

- Last updated on GMT

A woman suffering from constipation. © Getty Images
A woman suffering from constipation. © Getty Images

Related tags Constipation Probiotics Prebiotics synbiotics

Probiotic supplementation has been shown to increase stool frequency in adults suffering from constipation, new findings from a meta-analysis conducted by Chinese researchers have shown.

Stool consistency had also improved, and constipation symptoms reduced as seen from the findings published in Pharmacology and Therapeutics.

The meta-analysis was performed by researchers from Yancheng Third People’s Hospital, Huazhong University of Science and Technology, and The Affiliated Hospital of Xuzhou Medical University located in Jiangsu.

A total of 17 RCTs published before November 2022 were sieved from PubMed, Cochrane Library, and

The RCTs studied a total of 1,256 adults suffering from functional constipation, which is characterised by symptoms such as reduced bowel movements of less than three times per week, hard or lumpy stool, incomplete evacuation etc for at least six months. 

Of the 17 RCTs, 11 assessed the effects of probiotics versus placebo on bowel movement, while the remaining looked at the effects of synbiotics versus placebo. 

The probiotics studied consisted of both single and multi-strains products, with Bifidobacterium​ and Lactobacillus​ the most popular strains.

In the case of synbiotics, inulin, xylooligosaccharide, fructooligosaccharide, and psyllium husk were some examples of the prebiotics used.

Findings showed that probiotics usage had significantly increased stool frequency by 0.93 times per week as compared with placebo.

It also significantly improved stool consistency by 0.38 as compared with placebo, while constipation symptoms were down 0.28.

Effectiveness: Synbiotics then multi-strains

Synbiotics were found to be significantly more effective as compared to probiotics in terms of increasing stool frequency, though both had significantly improved bowel movements.

The researchers explained that this could be because prebiotics could be fermented by the gut microflora and produce short-chain fatty acids that stimulate bowel movements.

“We found that synbiotics had superior efficiency over probiotics in stool frequency, stool consistency (non-significance in synbiotics subgroup) and PAC-SYM (Patient Assessment of Constipation Symptom).

“In fact, another active ingredient in the product, prebiotics, also beneficially affected bowel function and relieve constipation. Fructooligosaccharides could be fermented by gut microflora accompanying the production of short-chain fatty acid which stimulate bowel movements.”

Within probiotics, multi-strains probiotics were found to have significantly increased stool frequency as compared to single strains formulations containing only Lactobacillus, ​or Bifidobacterium, ​or Bacillus ​subgroups – all of which did not produce significant improvements.

The finding is in line with previous research by Zhang et al​ and Miller et al, ​which found that multi-strains and formulations containing both Lactobacillus​ and Bifidobacterium​ could produce better results than single strain formulations alone.

“Bacillus-containing formula exhibits promising but non-significant efficacy and requires further validation; the multistrains formula displays satisfactory and credible efficacy, while synbiotics demonstrates superior efficacy compared with probiotics,” ​said the researchers.

Increase in abundance of specific strain

Lastly, the researchers found that probiotics might not affect α or β diversity of intestinal flora but could nonetheless increase the relative abundance of the specific strain(s) supplemented.

Alpha (α) and beta (β) diversity are used to examine microbiome diversity. The former measures how many types of species live in each area on a person or one sample, while the latter measures the differences in the microbiome composition between people or multiple samples.

Although probiotics supplementation did not lead to significant change in α or β diversity, the researchers said this also implied that the use of probiotics was safe.

“In α diversity, three of four studies showed that there was no significant change/difference, while in β diversity, three of four studies observed similar negative results, indicating that short-term supplementations of probiotics-containing products might not affect the stability in α or β diversity of intestinal flora.

“However, this did not mean the uselessness of probiotics-containing products, in the opposite, the minimal effect of probiotics-containing products on α or β diversity of intestinal flora might imply the safety.”


Source: Pharmacology and Therapeutics

Efficacy in bowel movement and change of gut microbiota on adult functional constipation patients treated with probiotics-containing products: a systematic review and meta-analysis

doi: 10.1136/bmjopen-2023-074557

Authors: Ding F, Hu M, Ding Y, et al

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