Nav: Home

Do probiotics have an effect on healthy adults? It's too early to tell

May 09, 2016

There is little evidence to support any consistent effect of probiotics on the gut microbiota of healthy individuals, according to a systematic review published in the open access journal Genome Medicine. The World Health Organization defines probiotics as live microorganisms which confer a health benefit to the host if administered in adequate amounts and probiotics products are often marketed toward the general population. However, evidence for their effects on bacteria living in the guts of healthy adults remains elusive.

The study by researchers at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen is a systematic review of seven randomized controlled trials (RCTs) investigating the effect of probiotic products on the fecal microbiota of healthy adults.

Nadja Buus Kristensen, PhD student and junior author, said: "According to our systematic review, no convincing evidence exists for consistent effects of examined probiotics on fecal microbiota composition in healthy adults, despite probiotic products being consumed to a large extent by the general population."

"A systematic review of experimental evidence allows us to pull together evidence and look at the relationship between probiotic products and the composition of the fecal microbiota in healthy people using explicit, systematic methods, ensuring the highest level of evidence," she said.

The researchers investigated RCTs for reported effects of probiotics on the overall structure of the fecal microbiota of healthy adults, including the number of species present, the evenness (distribution of species within the populations) and whether the probiotics groups of study participants as a result of the intervention had different changes in bacteria living in their gut than the placebo groups.

The authors found that of the seven original RCTs included in the study, only one observed significantly greater changes in the bacterial species composition of the fecal microbiota in individuals who consumed probiotics compared to those who did not.

Previous research has suggested an unbalancing effect of common disorders like obesity, diabetes, or colorectal cancer on the fecal microbiota and the therapeutic effects of probiotics have been studied in many diseases. Yet, while evidence of their effectiveness in metabolic and gastrointestinal disorders can be measured for example against body mass index, insulin resistance or the severity of gastrointestinal symptoms, measuring the effect of probiotics in healthy individuals is more difficult, according to the authors. Also, an international consensus on what defines a normal or healthy fecal microbial community is lacking.

To identify studies for inclusion in their systematic review, the authors conducted a literature search across three citation indices - PubMed, SCOPUS and ISI Web of Science. Studies were included based on study population (healthy adults), study design (RCT), means of intervention (probiotics or placebo), and intervention outcome (changes in the composition of the fecal microbiota). Studies were excluded if they were not RCTs, if they examined only effects within one group of individuals without comparing them to another, if they combined probiotics with other interventions or if they examined both healthy and unhealthy individuals.

Study participants across the seven original RCTs included in this review were healthy adults between 19 and 88 years of age. Numbers of individuals ranged from 21 to 81 and the proportion of women was between 50 and 100%. Probiotic products were administered as biscuits, milk-based drinks, sachets, or capsules for periods of 21 to 42 days.

The authors note that small sample sizes, variation in susceptibility to the probiotics between individual participants, use of different probiotic strains either in isolation or in combination and variations between the diets of individuals included in various study groups may have masked the true impact of probiotic intake.

Oluf Pedersen, professor at the University of Copenhagen and senior author of the paper said: "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. To explore the potential of probiotics to contribute to disease prevention in healthy people there is a major need for much larger, carefully designed and carefully conducted clinical trials. These should include ideal composition and dosage of known and newly developed probiotics combined with specified dietary advice, optimal trial duration and relevant monitoring of host health status."
-end-
Media Contact

Anne Korn
Press Officer
BioMed Central
T: +44 (0)20 3192 2744
E: anne.korn@biomedcentral.com

Notes to editor:

1. Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials

Nadja B. Kristensen, Thomas Bryrup, Kristine H. Allin, Trine Nielsen, Tue H. Hansen and Oluf Pedersen

Genome Medicine 2016

DOI: 10.1186/s13073-016-0300-5

For an embargoed copy of the research article please contact Anne Korn at BioMed Central.

After the embargo lifts, the article will be available at the journal website here: http://genomemedicine.biomedcentral.com/articles/10.1186/s13073-016-0300-5

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

2. An open access journal at the cutting edge of genomic and high-throughput technologies, medical discovery, and clinical application, Genome Medicine publishes high quality peer-reviewed articles of broad interest. Current areas of focus include precision medicine, novel methods and software, disease genomics and epigenomics, immunogenomics, infectious disease, microbiome, and systems medicine.

3. BioMed Central is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Nature, a major new force in scientific, scholarly, professional and educational publishing, created in May 2015 through the combination of Nature Publishing Group, Palgrave Macmillan, Macmillan Education and Springer Science+Business Media. http://www.biomedcentral.com

BioMed Central

Related Probiotics Articles:

Probiotics could improve survival rates in honey bees exposed to pesticide, study finds
In a new study from Lawson Health Research Institute (Lawson) and Western University, researchers have shown that probiotics can potentially protect honey bees from the toxic effects of pesticides.
Probiotics benefit in schizophrenia shaped by yeast infections
In a small pilot study of men with schizophrenia, researchers at Johns Hopkins Medicine and Sheppard Pratt Health System say they have evidence that adding probiotics -- microorganisms, such as bacteria found in yogurts -- to the patients' diets may help treat yeast infections and ease bowel problems.
Probiotics may not always be a silver bullet for better health
UNSW Sydney researchers have investigated the impact of probiotics on gut health and cognitive function.
Allergies? Probiotic combination may curb your symptoms, new study finds
As we head into allergy season, you may feel less likely to grab a hanky and sneeze.
Are prebiotics or probiotics effective against dermatitis?
Evidence supporting a key role for an altered gut microbiome in the development of atopic dermatitis (AD) would suggest that the use of probiotics or prebiotics to correct microbial imbalances in the gut could help prevent or treat AD.
More Probiotics News and Probiotics Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Teaching For Better Humans
More than test scores or good grades — what do kids need to prepare them for the future? This hour, guest host Manoush Zomorodi and TED speakers explore how to help children grow into better humans, in and out of the classroom. Guests include educators Olympia Della Flora and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...