Gut & microbiome
Gut flora, fibre and fermented foods.
72 answers, from 492 studies
Last updated: September 2026
Key questions
Which fermented products have the greatest effect on gut health?
Yoghurt and kefir have the most human evidence supporting a beneficial effect on gut health; for kimchi, kombucha and tempeh,…
Yes · Moderate evidence
Is fermented food good for your health and your microbiome?
Fermented food, and kefir and yoghurt in particular, likely has beneficial effects on gut flora and several health markers,…
Yes · Moderate evidence
Does long-term antibiotic use weaken your immune system?
Antibiotics disrupt the gut microbiota in ways that indirectly weaken your immune system; use them only when truly necessary…
Yes · Moderate evidence
Is there a link between oral bacteria and the development of Alzheimer's disease?
There is a consistent association between oral bacteria and Alzheimer's disease, but a proven cause-and-effect relationship in…
Moderate evidence
How does your microbiome affect your health and longevity?
Your microbiome is associated with how healthily you age, but whether you can deliberately steer it to live longer has not yet…
Preliminary evidence
What does a disrupted gut barrier do to the rest of your body?
A leaky gut barrier is associated with chronic inflammation and a range of diseases, from diabetes and joint complaints to…
Yes · Moderate evidence
Do probiotics help with irritable bowel syndrome itself, or only when taken alongside antibiotics?
Probiotics reduce irritable bowel symptoms without antibiotics, with Bacillus coagulans and Bifidobacterium strains having the…
Yes · Moderate evidence
Can you permanently change your gut microbiome through diet?
Diet does indeed change your gut microbiome, but lasting change requires lasting adjustment of your dietary pattern; a…
Moderate evidence
How much probiotic do you need per day?
There is no universal daily dose for probiotics: how much you need depends strongly on the bacterial strain, the application,…
Moderate evidence
Can probiotics improve your health in later life?
Probiotics may offer specific benefits for older adults, such as a better immune response and less constipation, but which…
Moderate evidence
Does eating a varied diet help your gut bacteria?
Fermented products have the strongest evidence base for increasing gut bacterial diversity. Eating broadly varied meals also…
Yes · Moderate evidence
Is fibre-maxxing (eating as much fibre as possible) healthy?
Eating more fibre is a good idea for most people in the West, but fibre-maxxing as an extreme principle offers no additional…
Yes · Moderate evidence
Can you strengthen your immune system by eating more fibre?
Eating more fibre has a clear biological mechanism, but in healthy people it does not automatically lead to a measurably…
Moderate evidence
What does the transition or menopause do to your gut microbiome?
Menopause is accompanied by measurable shifts in the gut microbiome, but how large these are and what they mean in practice…
Can you improve your gut microbiome by picking up bacteria while playing outside?
Playing outside exposes your child to more bacteria, and one small study observed a change in gut microbiome, but whether that…
Preliminary evidence
Can you see how fast you are ageing from your stool?
Your microbiome does change with age and is associated with health risks, but a reliable ageing test based on stool does not…
Moderate evidence
Are the gut bacteria of children different from those of adults?
Yes, the gut bacteria of children differ fundamentally from those of adults, with consequences for allergy and asthma risk. If…
Can an unhealthy gut contribute to skin problems such as acne or eczema?
A disrupted gut microbiome is associated with acne and eczema, although that association has not yet been proven to be cause…
Does chewing slowly really help with better digestion?
Chewing well certainly helps form a smooth food bolus and increases saliva production, but whether it actually leads to better…
Preliminary evidence
What does drinking coffee every day do to your gut bacteria?
Drinking coffee in moderation every day (up to 4 cups) is associated with a more favourable composition and greater diversity…
Can your gut microbiome affect your memory and concentration?
Your gut microbiome can influence your memory and concentration through several routes, but most of the evidence still comes…
What is the role of bile acids in healthy digestion?
Bile acids are indispensable for proper fat digestion and the absorption of fat-soluble vitamins. If you suffer from greasy…
What does smoking do to your gut and gut microbiome?
Smoking disrupts your gut microbiome and increases the risk of intestinal inflammation, gastrointestinal complaints and…
Does bone broth help your gut health?
The individual components of bone broth, such as certain amino acids, show favourable effects on the intestinal wall in…
Preliminary evidence
Can your gut microbiome influence inflammation in your body?
Your gut microbiome can influence inflammatory processes throughout your body via the gut wall. Eating more fibre and…
Does your gut microbiome affect how well you sleep?
Your gut microbiome and your sleep mutually influence each other, but how to practically steer that through probiotics or…
Are the gut bacteria of lean people different from those of heavier people?
The gut bacteria of people with excess weight differ measurably from those of lean people, but whether those bacteria are the…
What does a high-fat diet do to your gut microbiome?
A high-fat diet noticeably disrupts the gut microbiome: less bacterial diversity, more harmful species and a leaky gut wall…
Can you improve your gut bacteria by spending more time in nature?
Whether spending more time in nature improves your gut bacteria is a question the available studies cannot answer; if you want…
Preliminary evidence
Can certain fungi or bacteria in your gut influence your cellular ageing?
Certain gut bacteria produce substances that accelerate cellular ageing, while a diverse microbiome rich in fibre-fermenting…
Does drinking apple cider vinegar help your digestion?
There is no research whatsoever showing that apple cider vinegar improves digestion. If you want to use apple cider vinegar…
No · Preliminary evidence
Can your gut microbiome control your appetite and hunger?
Yes, your gut microbiome can influence your hunger and eating behaviour via a direct connection to your brain. Eating more…
What does eating too much sugar do to your gut health?
Eating a lot of sugar probably disrupts your gut microbiome and makes the gut wall more permeable, but it is the combination…
Does a healthy gut microbiome lead to better skin?
There are several indications that a healthy gut microbiome is beneficial for your skin, but how best to achieve that and…
Yes · Moderate evidence
Does eating flaxseed help your gut?
Through its fibre and lignans, flaxseed has a plausible positive effect on the gut, but for the gut as a specific target the…
Yes · Moderate evidence
Can your gut microbiome influence your risk of heart disease?
Your gut microbiome influences your heart health through metabolic by-products that can promote arterial hardening, high blood…
Yes · Moderate evidence
Can your microbiome reveal how old you are biologically?
Your microbiome does send signals about how you are ageing, but a reliable clinical test to measure your biological age with…
Is the appendix actually useful for your gut microbiome?
The appendix most likely does have a function: as a reservoir for healthy gut bacteria and as an immune organ. If you have…
What does fasting one day a week do to your gut microbiome?
Intermittent fasting demonstrably changes your gut microbiome, but the effects are likely temporary if you stop; for healthy…
Can your gut microbiome affect your cholesterol?
Your gut microbiome influences your cholesterol through bile acid conversion and the fermentation of fibres. Eating more fibre…
Does eating gluten-free help if you don't have coeliac disease?
For healthy people without coeliac disease or gluten sensitivity, eating gluten-free offers nothing and even carries a risk of…
No · Preliminary evidence
What do polyphenols, such as those found in berries and red wine, do to your gut bacteria?
Polyphenols from berries and red wine have a positive influence on your gut bacteria, but the human studies are still small;…
Are plant-based diets better for your gut than mixed diets?
A plant-based diet appears to be beneficial for your gut bacteria, but fermented foods perform at least as well in a direct…
Moderate evidence
Does fermented food like kimchi boost your immune system?
Kimchi and other fermented products can improve your gut microbiome and lower inflammatory markers, but whether that actually…
Preliminary evidence
Can exercise improve your gut microbiome?
Moderate regular exercise demonstrably improves your gut microbiome, but you need to keep exercising because the effect…
Yes · Moderate evidence
What are the signs that your gut flora is out of balance?
There are several recognisable signals, of which abdominal complaints such as persistent pain, diarrhoea, or constipation are…
Does green tea help your gut health?
Green tea extract showed measurable improvements in gut wall integrity and gut inflammation in a randomised trial; the signals…
Yes · Moderate evidence
How does your gut microbiome influence your hormone balance?
Your gut microbiome drives multiple hormones through enzymes, fermentation products and bile acids, ranging from oestrogen to…
What does too little sleep do to your gut?
Sleep deprivation may disrupt your gut microbiome, but we do not yet know with certainty how large that effect is in humans.…
Are abdominal pain and bloating signs of an unhealthy gut?
Abdominal pain and bloating usually do not indicate a damaged gut, but rather a functional condition such as IBS. If warning…
What does alcohol do to your gut microbiome?
Chronic heavy drinking demonstrably disrupts the gut microbiome, with consequences for the heart and liver. Moderate drinking…
Does intermittent fasting help your gut health?
For healthy people and people with metabolic syndrome there is reasonably consistent evidence that intermittent fasting has a…
Yes · Moderate evidence
Can stress really make your gut sick?
Stress really can make your gut sick: from abdominal pain and altered bowel habits to an increased risk of IBS and stomach…
What is the difference between probiotics and postbiotics?
Probiotics contain living bacteria; postbiotics contain inactivated variants or their building blocks. Postbiotics are safer…
Does eating garlic help your gut health?
There are preliminary indications that garlic is beneficial for gut health, with the strongest evidence being a randomised…
Yes · Moderate evidence
What does eating red meat do to your gut in the long term?
Eating a lot of red and processed meat measurably increases your risk of colorectal cancer, although for most people the…
What does alcohol do to your immune system?
Heavy or prolonged alcohol use clearly weakens your immune system and increases the risk of serious infections and liver…
Can your gut microbiome influence how long you live?
There are clear associations between a healthy, diverse gut microbiome and older age, but whether that microbiome promotes…
Preliminary evidence
Is my gut flora linked to being overweight?
Your gut microbiome is probably linked to excess weight through multiple mechanisms, but a proven causal relationship in…
Does eating a high-fibre diet help against constipation as you get older?
Eating more fibre helps against constipation in older adults, but the overall dietary pattern counts at least as much as fibre…
Yes · Moderate evidence
Does my gut microbiome change as I get older, and does it matter?
Yes, your gut microbiome changes measurably with age, but whether that matters depends strongly on your diet and lifestyle. A…
Yes · Strong evidence
Does leaky gut actually exist?
Leaky gut is a recognised biological phenomenon that is associated with various diseases, but whether it also causes those…
Do prebiotics, the fibres that feed your good bacteria, work just as well as probiotics?
Prebiotics alone are less effective than probiotics in the best-studied situations. For diarrhoea or immune support,…
No · Moderate evidence
What do artificial sweeteners do to your gut microbiome?
Whether artificial sweeteners truly disrupt your gut microbiome is not yet clear: studies contradict one another. Until there…
Can you restore your gut microbiome after a course of antibiotics?
Your gut microbiome partially recovers after a course of antibiotics, but a full return to its original state is rarely…
Moderate evidence
Can a disrupted gut microbiome weaken your immune system?
A disrupted gut microbiome demonstrably dysregulates your immune system and increases the risk of chronic inflammation. Eating…
Yes · Moderate evidence
Is there a real connection between your gut microbiome and your mood or brain?
There is a biologically plausible and, in animal research, robustly supported connection between your gut microbiome and your…
Does fermented food such as yoghurt, kefir and sauerkraut help your gut microbiome?
Fermented foods, and kefir and yoghurt in particular, have the strongest clinical support for a positive effect on the gut…
Yes · Moderate evidence
What does eating fibre do to your gut microbiome and your long-term health?
Fibre demonstrably feeds your gut bacteria, improves stool consistency and protects the gut wall. But how your microbiome and…
Do probiotic pills really help your gut?
Probiotics demonstrably work for acute diarrhoea, but for most other gut complaints it depends on which strain you take and…
Moderate evidence
Are fermented foods and probiotics good for your gut?
Fermented foods, particularly yoghurt and kefir, show positive indications for gut health; for most other products such as…
Yes · Moderate evidence
Are at-home microbiome tests worthwhile?
Commercial at-home microbiome tests are not clinically useful at this time: the advice is premature, the methods are not…
No · Moderate evidence
Latest articles
05 SepGut bacteria in infancy reshape the developing intestine
What happens in your gut during the first weeks of life may lay the groundwork for your health decades later.
1 min
A bacterial enzyme boosts cell energy in aging animals
An enzyme borrowed from bacteria makes the energy factories inside cells run more cleanly. In worms and mice, this reduced…
2 min
Exercise cuts a gut metabolite that harms bones
Regular exercise is known to protect bones. But new research reveals a specific biochemical link: physical activity lowers a…
1 min
Gut inflammation starts with a cell death switch
Crohn’s disease and ulcerative colitis cause persistent gut inflammation, yet their molecular triggers are not fully understood.
1 min
Exercise protects bones through gut bacteria
Exercise is good for your bones. That much has long been established. But the precise mechanism remained unclear.
2 min
Your gut bacteria shape how you age
Your gut bacteria do far more than digest food. They communicate constantly with your genes, immune system and brain. And as…
2 min
Gut bacterium slows ageing and extends healthy lifespan
A specific gut bacterium declines as we age. In mouse studies, supplementing with that bacterium, or with a compound it…
1 min
Air pollution speeds up Parkinson’s via the gut
Air pollution raises the risk of Parkinson’s disease. But the mechanism doesn’t run only through the lungs. A new analysis…
2 min
Mitochondria produce their own immune weapon
Mitochondria do more than generate energy. They also produce a peptide that directly attacks bacteria and reprograms immune…
2 min
Gut microbiome aging drives age-related disease
The composition of gut bacteria changes dramatically as you age. That has consequences for your entire body, from your immune…
2 min
Gut stem cells age through an inflammation signal
The lining of your gut is renewed constantly by stem cells. But with age, those stem cells falter.
1 min
Bile acids and gut bacteria age together
Your liver produces bile acids to digest fats. As you age, the composition of those bile acids shifts, and that shift appears…
2 min
Targeted light therapy clears gum bacteria linked to aging
Gum disease is not just a dental problem. Research suggests the bacterium driving gum inflammation also fuels age-related…
2 min
Stool transplant improves peanut tolerance in trial
Peanut allergy affects millions worldwide and has no real cure.
1 min
A gut bacterium in centenarians shields the intestinal wall
People who live to a hundred have a distinctly different gut microbiome. One bacterium stands out: Clostridium scindens.
2 min
Gut-derived TMAO raises atrial fibrillation risk
What your gut bacteria produce reaches directly into your heart.
1 min
Gut bacteria composition correlates with biological age
Your gut bacteria and your biological age are closely linked.
1 min
Brain peptide shapes learning and memory in the hippocampus
A neuropeptide long known as a digestive hormone turns out to play a key role in spatial learning and memory. Switching it off…
1 min
What actually makes your gut healthier, and what doesn't
Which food choices can genuinely strengthen your gut flora? Fibre plays the starring role, but fermented foods and cutting out…
3 min
Colon cancer is rising fast in people under fifty
Colorectal cancer has long been seen as a disease of older age. But younger adults are increasingly being diagnosed, often too…
2 min
Gut microbiome diversity links to frailty in older women
Women aged 75 to 80 with less diverse gut microbiomes are more likely to fall, fracture a hip, or die earlier.
2 min
Gut bacteria metabolite speeds up brain aging
A compound made by gut bacteria appears to damage the brain. And the older you get, the more of it circulates in your blood.
2 min
Lifestyle slows biological aging on the clock
Twelve weeks of exercise, dietary guidance and probiotic yogurt, and a biological aging clock moved. Can a simple lifestyle…
2 min
Immune cells guard the gut microbiome into old age
The composition of your gut bacteria shifts as you age. But why exactly?
1 min
Ecological rules decide who wins in your gut
Your gut is an ecosystem, much like a forest or an ocean. New insights show that ecological rules, competition for food and…
1 min
Protein labelling keeps the gut lining healthy
Your gut lining renews itself constantly. Two proteins that help cells manage their own building blocks play a larger role in…
1 min
Blood metabolites link midlife lifestyle to brain aging
What your blood looks like at fifty may predict how your brain holds up at seventy. A large study now maps that connection…
2 min
Plant extract reduces gut inflammation in animals
A plant extract long used in Southeast Asian traditional medicine significantly reduced signs of gut inflammation in animal…
1 min
A gut bacterium protects aging lungs from scarring
Pulmonary fibrosis is a serious condition in which lung tissue progressively stiffens and suffers irreversible damage.…
2 min
Primate guts reveal ageing at the single-cell level
The small intestine ages, and that process has now been mapped in detail at the level of individual cells for the first time.
1 min
Your immune system polices your gut bacteria
Your immune system doesn’t just keep pathogens out. It also actively controls which gut bacteria get space to grow and which…
2 min
Ultra-processed food quietly harms your attention
You can eat a generally healthy diet and still suffer cognitively if ultra-processed foods are part of the picture.
2 min
A synthetic gut microbiome could replace stool transplants
A stool transplant from a young donor can fully reset the gut microbiome of an older recipient. But regulation makes it…
2 min
Ultra-Processed Food Is More Complicated Than It Looks
Ultra-processed food seems unhealthy. But scientists are far from agreed on why, or whether all ultra-processed products are…
2 min
One gut microbe raises your sepsis risk
Sepsis is a life-threatening condition where infection triggers uncontrolled inflammation and organ failure. New research…
2 min
Gut bacteria restore quality in aging eggs
Egg quality declines faster than most other parts of the body. Now it turns out gut bacteria may slow that decline, through a…
2 min
Leading scientists demand action on ultra-processed food
Top nutrition researchers rarely agree this loudly. Ultra-processed food damages health, they say, and the system producing it…
1 min
Beta-glucan calms the immune system in gut disease
Your immune system can learn from an infection and respond faster next time. That sounds helpful. But in chronic gut…
2 min
Amino Acid Deficiency Triggers Brain
You eat something, and your body knows almost immediately whether it contains enough building blocks. But how?
2 min
Ultrasound reshapes gut bacteria to aid muscles
Sound waves directed at the abdomen seem like an unlikely tool for improving muscle function.
1 min
Living implant delivers drugs using contained bacteria
An implant that monitors when to release medication and produces that medication itself. Researchers have achieved this using…
2 min
Bacterial toxin primes aged skin to heal better
Aged skin heals poorly. But a toxic bacterial substance, given before an injury occurs, makes that skin noticeably better at…
2 min
Bacterial vesicles accumulate and damage brain tissue
Every bacterium in your body constantly sends out tiny molecular packages. A new hypothesis proposes that the build-up of…
2 min
The gut bacteria that act as traffic controllers for your immune system
A dietary amino acid shapes gut barrier function and immune regulation through a microbial pathway that has only recently been…
2 min
Aging gut tissue isn’t just changing, it’s actively inviting harmful bacteria in
The bacterial community living in your gut shifts as you age, becoming less diverse, more inflammatory. For years, researchers…
2 min
How Your Gut Ages, and Rolls Out the Welcome Mat for Harmful Bacteria
Something fundamental shifts in your gut as you age, and that shift makes it easier for dangerous bacteria to take hold.…
2 min
A mouth bacterium that both promotes and fights cancer
Fusobacterium nucleatum is a bacterium that normally lives in your mouth but is also found deep inside tumors. Scientists have…
1 min
A Tiny Worm Uses Its Nose to Hunt Down the Best Protein, and It May Tell Us Something About Aging
A worm barely a millimeter long can sniff out bacteria enriched with a specific amino acid it cannot make itself.
2 min
Naked mole-rats age for decades without their gut bacteria changing, that’s almost unheard of
In most mammals, the community of bacteria living in the gut shifts dramatically with age.
2 min
The gut bacteria that may decide how active older people stay
Older adults who exercise regularly have measurably different gut bacteria than those who don’t.
2 min
How gut bacteria shape whether older people stay active
Older people who move more have a measurably different gut microbiome than those who rarely get off the couch. But which way…
2 min
A longevity gene in flies works partly through gut bacteria
A gene associated with longer lifespan in fruit flies for decades appears to work partly through the animal’s gut bacteria.
2 min
Scientists image the molecular pump that lets bacteria shrug off antibiotics
Antibiotic resistance is one of medicine’s most pressing threats, and one of bacteria’s cleverest tricks is simply pumping…
2 min
Cells keep changing their internal makeup, yet something always stays the same
Bacterial cells can radically shift their internal molecular composition in response to changing conditions. Yet something…
2 min
Tuberculosis hides inside our immune cells. Scientists just found two proteins that help unmask it
Tuberculosis kills more people each year than almost any other infectious disease. The bacterium survives by hiding inside the…
2 min
Pesticides may be quietly disrupting the bacteria that keep you healthy as you age
Pesticides are designed to kill pests. But a growing body of research suggests they may also be damaging the bacteria in our…
2 min
AI Decoded a Hidden Immune Arsenal That Bacteria Developed Over Billions of Years
Bacteria have been fighting viruses for billions of years, and in doing so have evolved a vast and largely unknown arsenal of…
2 min
The bacteria in your mouth may be quietly damaging your brain
We’ve known for years that gum disease is bad for your heart.
2 min
How Tuberculosis Hacks the Nucleus to Hide from Immunity
Tuberculosis bacteria survive inside the very immune cells meant to destroy them.
2 min
How bacteria trick your immune system
Tuberculosis bacteria survive in the body by hiding inside your own cells.
2 min
Gut bacteria don’t just live in the intestine, they help run it from birth
The importance of gut bacteria in early life is well established.
2 min
Gut bacteria and gut movement: how microbes kick-start digestion in newborns
We already know that gut bacteria matter in newborns. But exactly how they help drive gut motility early in life is a question…
2 min
Can Rebalancing Your Gut Bacteria Slow Brain Decline?
The gut microbiome sends a constant stream of chemical signals to the brain.
2 min
How gut bacteria may be slowly breaking down your brain, and what science is doing about it
Your gut microbiome sends messages directly to your brain through metabolites and inflammatory signals.
2 min
Eating less protein reshapes your fat tissue - and your gut bacteria are doing the work
Restricting protein triggers a conversion of white fat into brown fat, a metabolically healthier tissue type. But the body…
2 min
Old gut microbiome makes young mice age faster — what does that mean for us?
A fecal transplant from old mice to young mice measurably accelerates aging.
2 min
Gut microbiome aging clocks: do they actually measure biological age?
Take enough data from enough people, run an algorithm over it, and you have an aging clock. That now applies to the gut…
2 min
How Stress Hijacks the Brain’s Habit System to Drive Alcohol Relapse
Stress is the most reliable trigger for alcohol relapse. A new study in mice and rats maps the specific neural circuit…
2 min
Tuberculosis and genetic ancestry: how co-evolution shapes who gets sick
Tuberculosis kills more than a million people every year. Yet only a small fraction of those who breathe in the bacteria ever…
2 min
Your immune system as gardener: how aging loses control of your gut bacteria
The composition of the gut microbiome shifts with age, and not for the better. But why, exactly?
2 min
Your gut microbiome controls how well mRNA medicines and viral vectors work in your body
A new study in Science reveals that the bacteria living in your gut directly influence how effectively synthetic and viral…
1 min
Gut bacteria weigh the costs before going to war with their rivals
New research shows that gut bacteria don't simply unleash their chemical weapons on competitors whenever they can. They run a…
1 min
Gut bacteria, nitrate, and kidney failure: how your microbiome can accelerate chronic kidney disease
A study in the leading journal Science reveals a surprising mechanism behind chronic kidney disease: gut bacteria use nitrate…
1 min
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