34 studies

Gut & Microbiome

Gut & Microbiomepreliminary · human dataAdded 6 October 2026
Fibre eases constipation and nudges gut-brain chemistry too
A meta-analysis of 14 randomised trials in 1,284 people with functional constipation found fibre supplements added 1.42 bowel movements a week and improved stool consistency, with soluble, fermentable fibres above 10 g a day for at least 4 weeks working best. Fibre also shifted gut-brain markers such as short-chain fatty acids and serotonin, though the clinical meaning of those changes is not yet established.
What it shows: Solid for the symptom relief, speculative for the brain story: results pooled from 14 trials in 1,284 people, with moderate to high certainty for the bowel outcomes. The biomarker shifts only hint at a mechanism and do not prove fibre acts on the gut-brain axis.Study · Clin Transl Gastroenterol
Full breakdown →Fibre explained The Impact of Dietary Fiber Supplementation on Gut-Brain Axis Biomarkers and Symptoms in Functional Constipation: A Meta-Analysis of Randomized Controlled Trials. Clin Transl Gastroenterol 2026
Gut & Microbiomepreliminary · human dataAdded 5 October 2026
A 20-minute walk got the gut moving within minutes
In a small study of 21 healthy adults, a 20-minute treadmill walk significantly increased bowel sounds, an indirect marker of gut motility, within 1 to 2 minutes of finishing the walk.
What it shows: Early days: a small lab study in 21 healthy adults that used bowel sounds as a stand-in for gut movement, so it cannot say whether walking actually relieves constipation. Nobody in the study had bowel problems, and the recording stopped 15 minutes after the walk.Study · Sci Rep
Full breakdown →Immediate effect of physical activity on gut motility in healthy adults. Sci Rep 2025
Gut & Microbiomewell supported · human dataAdded 30 September 2026
Probiotics left the gut-linked blood marker TMAO unmoved
Probiotic supplements had no significant effect on blood levels of TMAO, a metabolite regulated by gut bacteria, in results pooled from 8 trials with 270 adults. A possible larger reduction in people under 50 remains unconfirmed.
What it shows: A clear null but from thin data: pooled results from 8 trials covering just 270 adults, so a small real effect could still hide in numbers that size. The suggestion that people under 50 respond differently comes from slicing the data into subgroups and needs its own test.Meta-analysis · Clin Nutr ESPEN
Full breakdown →Gut microbiome explained Impact of probiotic supplementation on trimethylamine N-oxide (TMAO) in humans: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr ESPEN 2022
Gut & Microbiomepreliminary · human dataAdded 28 September 2026
Probiotics lowered key inflammation markers in adults with depression
Pooled results from ten randomised trials in 486 adults with depression found probiotic supplementation lowered the inflammatory markers C-reactive protein and TNF-α, with a borderline drop in IL-1β. Two other markers, IL-6 and IL-10, did not change significantly.
What it shows: Reasonably solid as far as it goes: results pooled from ten trials covering 486 adults with depression. The drops were in blood markers of inflammation rather than in mood itself, and the authors say larger, longer trials are still needed to confirm the effect and find the best formulations.Review · Prog Neuropsychopharmacol Biol Psychiatry
Full breakdown →Probiotics explained Effects of probiotic supplementation on inflammatory biomarkers in patients with depression: A systematic review and meta-analysis of randomized controlled trials. Prog Neuropsychopharmacol Biol Psychiatry 2026
Gut & Microbiomewell supported · human dataAdded 27 September 2026
Adding a probiotic helped H. pylori treatment succeed, with fewer side effects
Adding Lactobacillus probiotics to standard Helicobacter pylori eradication therapy was linked to a 10% relative increase in treatment success and a 30% relative drop in side effects across 32 randomised trials of 4,010 patients. The eradication benefit appeared only with triple therapy regimens, and the side effect reduction only in adults.
What it shows: Solid as pooled evidence goes: results pooled from 32 trials in 4,010 people pointed the same way for both success and side effects. The eradication boost showed up only alongside triple therapy, so it may not help with other antibiotic regimens.Meta-analysis · Eur J Clin Pharmacol
Full breakdown →Probiotics explained Effectiveness of Lactobacillus-supplemented eradication therapy for Helicobacter pylori: a systematic review and meta-analysis of randomized controlled trials. Eur J Clin Pharmacol 2026
Gut & Microbiomepreliminary · human dataAdded 18 September 2026
Gut bacteria help predict whose fasting weight loss lasts
A 5-day fast in 38 healthy adults cut body mass index mostly through fat loss, with improvements partially persisting 12 weeks later; a model built on baseline gut microbiome and clinical measures predicted who kept the weight off, and it held up in three independent fasting cohorts.
What it shows: Early but intriguing: one small trial in 38 healthy adults, so the prediction idea needs bigger groups before anyone plans a fast around their gut bacteria. It helps that the model held up in three separate fasting cohorts, including people fasting far longer.RCT · Genome Med
Full breakdown →Gut microbiome explained Calorie Deficit Calculator Machine learning identifies microbiome and clinical predictors of sustained weight loss following prolonged fasting. Genome Med 2026
Gut & Microbiomewell supported · human dataAdded 17 September 2026
Probiotics nudged mood, anxiety and stress in healthy adults
Pooling seven randomised placebo-controlled trials in healthy adults, probiotic supplementation produced a small but statistically significant improvement in symptoms of depression, anxiety and perceived stress compared with placebo.
What it shows: Decent evidence for a small effect: results pooled from seven trials in healthy volunteers, all of which passed a quality check. Everyone studied was healthy, so this says nothing about treating diagnosed depression or anxiety.Meta-analysis · J Altern Complement Med
Full breakdown →Probiotics explained Probiotics and Subclinical Psychological Symptoms in Healthy Participants: A Systematic Review and Meta-Analysis. J Altern Complement Med 2017
Gut & Microbiomewell supported · human dataAdded 15 September 2026
No consistent gut signature behind stress-busting probiotics in 29 trials
A sweep of 29 randomised trials found that stress-targeting interventions, from psychobiotic supplements to diets and lifestyle programmes, produced no consistent gut microbiome signature, and improvements in stress did not reliably move in parallel with microbiome changes.
What it shows: The absence of a pattern carries weight because this was a sweep of all 29 randomised trials on the question. But those trials differed so much in people, products and measurement methods that the reviewers could only compare them narratively, so a real signal could still be hiding in the noise.Systematic review · Nutrients
Full breakdown →Probiotics explained Targeting Stress and the Gut-Brain Axis: Effects of Lifestyle and Psychobiotic Interventions on the Gut Microbiome in Adults-A Systematic Review of Randomized Controlled Trials. Nutrients 2026
Gut & Microbiomepreliminary · human dataAdded 6 September 2026
Synbiotics improved blood sugar control in diabetes, but left LDL untouched
Pooled results from seven randomised trials suggest synbiotic supplements improve fasting glucose, insulin levels, insulin resistance, triglycerides and total cholesterol in people with diabetes, but have no effect on LDL or HDL cholesterol.
What it shows: Promising but thin: results pooled from just seven trials in people with diabetes, and several of the improvements only just cleared the bar for statistical significance. Different products and doses across the trials mean a couple of new studies could shift the picture.Meta-analysis · Probiotics Antimicrob Proteins
Full breakdown →Insulin sensitivity explained Metabolic Fitness Index The Effects of Synbiotic Supplementation on Glucose Metabolism and Lipid Profiles in Patients with Diabetes: a Systematic Review and Meta-Analysis of Randomized Controlled Trials. Probiotics Antimicrob Proteins 2018
Gut & Microbiomewell supported · human dataAdded 4 September 2026
Probiotics nudge blood sugar down in people with diabetes
Pooled results from 41 randomised trials in 2991 people with diabetes found probiotics and synbiotics modestly improved long-term blood sugar (HbA1c), fasting glucose and insulin levels. Supplements containing multiple species were particularly effective for HbA1c.
What it shows: Solid enough to take seriously, but the benefit is modest rather than dramatic: results pooled from 41 trials in 2991 people with diabetes. The trials disagreed with each other a fair amount, and which strains work best is still unsettled.Meta-analysis · Clin Nutr
Full breakdown →Insulin sensitivity explained Probiotics and synbiotics for glycemic control in diabetes: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr 2024
Gut & Microbiomewell supported · human dataAdded 2 September 2026
Synbiotics trimmed weight, waist and cholesterol in metabolic syndrome
In people with metabolic syndrome, synbiotic supplements reduced insulin, triglycerides, total and LDL cholesterol, systolic blood pressure and waist circumference, and cut body weight by 4.3 kg on average across pooled trials. Fasting glucose, BMI, diastolic blood pressure and C-reactive protein did not change significantly.
What it shows: Encouraging but resting on just five trials with 1049 people, all with metabolic syndrome, and the trials often disagreed on how large the benefits were, so the exact numbers deserve caution.Meta-analysis · Pharmacol Res
Full breakdown →Metabolic syndrome explained Metabolic Fitness Index Impact of synbiotic supplementation on cardiometabolic and anthropometric indices in patients with metabolic syndrome: A systematic review and meta-analysis of randomized controlled trials. Pharmacol Res 2022
Gut & Microbiomewell supported · human dataAdded 31 August 2026
Probiotics' brain benefits pass a strict evidence audit
An umbrella review of 17 meta-analyses, covering 156 randomised trials of probiotics in adults, found that the beneficial associations with cognitive health outcomes are supported by moderate to high quality evidence, though the best strains, doses and durations remain unclear.
What it shows: Stronger than the usual supplement story: a sweep of 17 pooled analyses covering 156 trials rated many probiotic and cognition links as moderate or high quality evidence. The underlying trials were small, 37 to 409 people, and ran from under a week to 28 weeks, so which strains and doses actually work is still an open question.Systematic review · Nutr Rev
Full breakdown →Probiotics explained Probiotics and Cognitive-Related Health Outcomes: An Umbrella Review of Systematic Reviews and Meta-Analyses of Randomized Controlled Trials. Nutr Rev 2025
Gut & Microbiomewell supported · human dataAdded 30 August 2026
Probiotics nudged blood sugar down in people with diabetes
In pooled data from 12 randomised trials of 1113 people with diabetes or prediabetes, adding probiotics to standard care raised gut Lactobacillus and Bifidobacterium levels and modestly reduced fasting blood glucose. Courses of three months or less showed the clearest improvements in blood sugar markers.
What it shows: Reasonably solid on direction, less so on size: results pooled from 12 trials in 1113 people with diabetes or prediabetes, but the trials disagreed with each other a great deal on the microbe changes. The drop in fasting glucose was modest, and everyone here was on standard diabetes care, so this says nothing about healthy people.Meta-analysis · Br J Nutr
Full breakdown →Insulin sensitivity explained Metabolic Fitness Index Effects of probiotic supplementation on intestinal microbiota in patients with diabetes/prediabetes: a systematic review and meta-analysis of randomized controlled trials. Br J Nutr 2026
Gut & Microbiomewell supported · human dataAdded 30 August 2026
Probiotics did not make healthy guts more diverse
Pooled data from 22 randomised trials covering 1068 healthy people found probiotic supplements produced no significant change in gut microbiota diversity on any of four standard indices. The result held regardless of probiotic family or how long people supplemented.
What it shows: A convincing null for the healthy shopper: results pooled from 22 trials in 1068 healthy people found no shift on any of four diversity measures, and the finding held across probiotic types, study quality and course length. Diversity is only one way of judging gut health, so this does not rule out other effects.Meta-analysis · BMC Med
Full breakdown →Gut microbiome explained Effect of probiotic supplementation on the gut microbiota diversity in healthy populations: a systematic review and meta-analysis of randomised controlled trials. BMC Med 2026
Gut & Microbiomewell supported · human dataAdded 25 August 2026
Probiotics do nothing for your thyroid hormones
Pooled results from eight randomised trials show probiotic and prebiotic supplements do not change thyroid hormone levels, with TSH, free T4 and free T3 all unmoved. The only significant effect was a modest drop in thyroid antibodies in people with Graves' disease.
What it shows: A solid null for healthy thyroids: results pooled from eight trials found no movement in any thyroid hormone measured. The antibody reduction applies to people with Graves' disease, a diagnosed autoimmune condition, not to healthy supplement users.Meta-analysis · PLoS One
Full breakdown →Probiotics explained Effect of probiotics or prebiotics on thyroid function: A meta-analysis of eight randomized controlled trials. PLoS One 2024
Gut & Microbiomepreliminary · human dataAdded 25 August 2026
Antibiotics you took years ago still show up in your gut
In an Estonian cohort of 2,509 people with shotgun metagenomic gut sequencing linked to health records, past medication use was associated with the gut microbiome, with traces of antibiotics, psycholeptics, antidepressants, proton pump inhibitors and beta-blockers still detectable several years after use. In a subgroup of 328 people sampled twice, similar shifts appeared after starting or stopping treatment.
What it shows: Suggestive rather than settled: researchers followed 2,509 people rather than testing drugs on them, so they cannot prove the medicines caused the differences, though repeat samples in 328 people showing shifts after starting or stopping treatment point that way.Study · mSystems
Full breakdown →Biological age explained Phenotypic Age Calculator A hidden confounder for microbiome studies: medications used years before sample collection. mSystems 2025
Gut & Microbiomewell supported · human dataAdded 23 August 2026
Probiotic brain benefits vanish when the trials are pooled
Pooled across 22 randomised trials in 1551 people, probiotics, prebiotics and fermented foods produced no significant improvement in global cognition or in any individual cognitive domain, despite 14 individual studies reporting benefits.
What it shows: A trustworthy null: results pooled from 22 trials in 1551 people, most of them well run, found no cognitive benefit anywhere. The trials were small and short, so a subtle long-term effect cannot be fully ruled out.Meta-analysis · Neurosci Biobehav Rev
Full breakdown →Executive function explained Prebiotics, probiotics, fermented foods and cognitive outcomes: A meta-analysis of randomized controlled trials. Neurosci Biobehav Rev 2020
Gut & Microbiomewell supported · human dataAdded 23 August 2026
Fibre feeds good gut bacteria and trims cholesterol in type 2 diabetes
In people with type 2 diabetes, dietary fibre increased the beneficial gut bacterium Bifidobacterium and lowered circulating lipopolysaccharide, total cholesterol and BMI compared with control diets, but left triglycerides, HDL, LDL and most inflammatory markers unchanged.
What it shows: Modest and mixed: results pooled from up to 11 trials in people with type 2 diabetes, with some outcomes resting on barely more than a hundred participants. Short trials and very different fibre types and amounts make the true size of the benefit uncertain.Meta-analysis · Nutrients
Full breakdown →Insulin sensitivity explained The Effect of Dietary Fibre on Gut Microbiota, Lipid Profile, and Inflammatory Markers in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Nutrients 2021
Gut & Microbiomepreliminary · human dataAdded 23 August 2026
One gut bacterium, not its close relatives, tracks with stronger grip
Higher relative abundance of the gut species Roseburia inulinivorans, but not of other Roseburia species, was associated with stronger handgrip, leg press and bench press in adults, and the species was less abundant in older adults than younger ones. Supplementing it in antibiotic-treated mice increased forelimb grip strength, alongside larger muscle fibres and a shift from type I to type II fibres.
What it shows: Early and split evidence: in people this is only an association between one gut species and strength scores in groups of younger and older adults, and the test of cause was done in mice given antibiotics. Nobody has yet given this bacterium to humans to see whether strength changes.Study · Gut
Full breakdown →Grip strength explained Roseburia inulinivorans increases muscle strength. Gut 2026
Gut & Microbiomewell supported · human dataAdded 22 August 2026
The over-60 gut still listens: supplements shift its bacteria
Across 29 randomised trials in 1,633 adults aged 60 and over, probiotic, prebiotic and synbiotic supplements raised beneficial gut bacteria such as Bifidobacterium, increased microbial diversity and lowered several inflammatory markers.
What it shows: Encouraging but indirect: results pooled from 29 trials in 1,633 people aged 60 and over show shifts in bacteria and blood markers, not fewer illnesses or better strength or function. Different supplement types did different things, so no single product is proven here.Meta-analysis · Nutr J
Full breakdown →Gut microbiome explained Effects of probiotics, prebiotics, and synbiotics on gut microbiota in older adults: a systematic review and meta-analysis of randomized controlled trials. Nutr J 2025
Gut & Microbiomewell supported · human dataAdded 22 August 2026
Probiotics trim diabetic waists by less than a centimetre
In pooled trials of people with type 2 diabetes, microbiome therapies trimmed waist circumference by just 0.97 cm on average, and only probiotics reached significance at 0.62 cm, while blood sugar measures improved more consistently.
What it shows: Believable but tiny: results pooled from 15 trials covering 443 treated and 387 control participants with type 2 diabetes, and the waist change is under a centimetre. The blood sugar improvements were more consistent than the waist ones, and prebiotics and synbiotics actually raised fasting insulin.Meta-analysis · J Acad Nutr Diet
Full breakdown →Visceral fat explained Body Fat Calculator The Effect of Microbiome Therapies on Waist Circumference, a Measure of Central Obesity, in Patients with Type 2 Diabetes: A Systematic Review and Meta-analysis of Randomized Controlled Trials. J Acad Nutr Diet 2023
Gut & Microbiomewell supported · human dataAdded 21 August 2026
Multi-strain probiotics beat single strains for constipation relief
A meta-analysis of 15 randomised trials found probiotics cut whole-gut transit time by 13.75 hours and added about one bowel movement per week in adults with functional constipation, with multi-strain products delivering benefits that single strains did not.
What it shows: Among the better evidence you will find on this topic: results pooled from 15 trials in adults with functional constipation. But the trials were often poorly reported and participants usually knew what they were taking, so the true benefits may be smaller than these numbers suggest.Meta-analysis · Clin Nutr
Full breakdown →Probiotics explained Meta-analysis of randomized controlled trials of the effects of probiotics on functional constipation in adults. Clin Nutr 2020
Gut & Microbiomepreliminary · human dataAdded 20 August 2026
Probiotics nudge cholesterol down, but only by a little
Across 155 randomised trials in 9,906 people, probiotic supplements modestly improved blood lipids: triglycerides fell by 10.83 mg/dL on average, total cholesterol by 8.46 mg/dL, LDL cholesterol by 5.83 mg/dL, and HDL cholesterol rose by 1.28 mg/dL.
What it shows: Large and consistent: results pooled from 155 trials in 9,906 people all pointed the same way, so the effect looks real. It is also small, and the trials used many different strains and doses, so no single product can claim these numbers.Review · Crit Rev Food Sci Nutr
Full breakdown →ApoB explained Heart Age Calculator Effects of probiotic intervention on serum lipid profiles: current evidence from systematic review and meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr 2026
Gut & Microbiomepreliminary · human dataAdded 20 August 2026
Short on fibre, gut bacteria start chewing your own gut lining
Isotope-tracing work found that two phenol compounds considered uremic toxins come from gut bacteria breaking down the body's own secreted proteins such as mucins, while the beneficial-looking phenols hippuric acid and 3-phenylpropionate come from dietary protein that resists digestion. Fibre reduced bacterial digestion of those host proteins and so suppressed the toxin-type phenols.
What it shows: Mechanism work, not a diet result: it explains how fibre and hard-to-digest plant protein shift bacterial metabolites, but the abstract reports no health outcomes, so nobody has shown this changes how anyone feels or lives.Study · Proc Natl Acad Sci U S A
Full breakdown →Essential amino acids explained Protein Intake Calculator Digestion-resistant proteins support the healthy metabolite profiles associated with plant-based diets. Proc Natl Acad Sci U S A 2026

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