How to improve gut health: 9 evidence-based steps

By the DieticiansWorldwide.com editorial team · 18 October 2026 · Clinical nutrition

What "gut health" actually means

"Gut health" has no clinical definition. In everyday use it covers three different things: a digestive system that works comfortably (regular, formed stools, little pain or bloating), a gut lining that does its job as a barrier, and a diverse community of microbes living in the large bowel. Research has linked that microbial community to immunity, metabolism and even mood, but most of those links come from observational studies and animal work. They show association, not proof that changing your microbes will change your health.

That gap matters, because it is where most gut health marketing lives. The steps below are ordered by how much evidence supports them, and they are mostly about food and habits rather than products. If you want to know which supplements are worth buying, our guide to gut health supplements ranks them separately; this guide is about the foundations that work with or without a capsule.

One caution before you start. A "gut health" plan is for people who feel broadly well and want to look after their digestion. New, persistent or severe symptoms need a diagnosis first, and the warning signs are listed later in this guide.

The 9 steps at a glance

Step 1: Reach your fibre target, slowly

Fibre is the food your gut microbes depend on, and it is the one change with a strong evidence base. Government guidelines say adults should increase their intake to 30 g a day, while most adults in the UK eat an average of about 20 g, according to the NHS. Children need less: about 15 g at 2 to 5 years, 20 g at 5 to 11 and 25 g at 11 to 16.

The case for closing that gap is not only about digestion. A series of systematic reviews and meta-analyses commissioned to inform WHO recommendations pooled 185 prospective studies and 58 clinical trials (Reynolds and colleagues, Lancet 2019). Comparing the highest fibre eaters with the lowest, the observational data showed a 15 to 30% reduction in deaths, both overall and from heart and circulatory disease, alongside fewer cases of coronary heart disease, stroke, type 2 diabetes and bowel cancer. The greatest risk reduction came with 25 to 29 g a day. The authors graded the certainty of evidence for fibre as moderate.

Fibre is enjoying a moment in the spotlight, too. Social media has embraced "fibremaxxing", the habit of loading every meal with as much fibre as it will take, and some food brands now talk about fibre the way they once talked about protein. The direction is right. The speed is often wrong. Jumping from 15 g to 40 g in a week is a reliable route to wind, cramps and bloating, and many people give up.

How to do it well:

• Add one source at a time and increase over two to three weeks.
• Spread it across the day rather than loading one meal.
• Mix types: oats, beans, lentils, wholegrains, vegetables, fruit, nuts and seeds each bring different fibres.
• Drink more as you go (see step 4).

Our high-fibre foods list shows how many grams common portions provide, which makes the target far easier to plan. If food alone falls short, a supplement such as psyllium can bridge the gap, and our guide to choosing a fibre supplement compares the options.

Try the free fibre calculator

Step 2: Eat a wider variety of plants

Total fibre is one measure. Variety is another. Different microbes prefer different fibres and plant compounds, so a narrow diet tends to support a narrower community.

The most quoted evidence comes from the American Gut Project, a citizen science study of more than 10,000 people, mainly in the United States, United Kingdom and Australia (McDonald and colleagues, mSystems 2018). Participants who reported eating more than 30 different types of plants a week had more diverse gut microbes than those eating 10 or fewer, along with more bacteria associated with fermenting fibre and fewer antibiotic resistance genes. This is where the popular "30 plants a week" target comes from.

It is worth being clear about what that study was. Participants were self-selected volunteers, plant intake was self-reported, and the findings are associations. People who eat 30 different plants also tend to differ in many other ways. The study does not prove that 30 is a magic number, or that counting plants improves health.

Even so, variety is a sensible, low-risk goal that pushes your diet in the right direction. Practical ways to widen it without overhauling your shopping:

• buy mixed bags of beans, frozen vegetables, nuts or seeds rather than single types;
• rotate your wholegrains: oats, barley, brown rice, rye, buckwheat;
• add herbs and spices, which count as plants in most counting schemes;
• swap one familiar vegetable a week for one you rarely buy.

Step 3: Add some fermented foods

Fermented foods are defined by the International Scientific Association for Probiotics and Prebiotics as "foods made through desired microbial growth and enzymatic conversions of food components" (ISAPP consensus statement, 2021). That definition is broader than many people expect. It includes yoghurt, kefir, cheese, sauerkraut, kimchi, miso, tempeh, kombucha, sourdough bread and even wine and beer.

Two points follow from it. First, not every fermented food still contains live microbes when you eat it. Baking, pasteurising and canning after fermentation kill them, which is why sourdough and most shelf-stable pickles do not deliver live cultures. Second, fermented foods are not automatically probiotics, a term reserved for defined strains with demonstrated benefits. The ISAPP statement draws that line explicitly.

So are fermented foods good for gut health? There are encouraging signals, including a small randomised trial at Stanford, discussed in our guide to probiotics, in which a high fermented-food diet increased microbial diversity in healthy adults. But the trials so far are small and short. A daily portion of plain yoghurt or kefir, or a spoonful of live sauerkraut or kimchi with meals, is a reasonable addition for most people. Start small, because some fermented foods are high in salt, and some (such as kombucha and kimchi) can upset sensitive stomachs.

Confused by the jargon on yoghurt pots and supplement labels? Our explainer on prebiotics versus probiotics untangles the terms.

Step 4: Drink enough fluid

Fibre works by holding water in the bowel. Without enough fluid, a high-fibre diet can make constipation worse rather than better. The NHS advises keeping well hydrated, especially with water, and suggests a glass of water with every meal as a simple habit (NHS, good foods for digestion). The same page recommends limiting caffeinated and fizzy drinks if they trigger heartburn or other symptoms.

You do not need to force large volumes. Pale yellow urine and comfortable, soft stools are better guides than a fixed number of litres. Our free water intake calculator shows a daily target based on European adequate intakes, including water from food.

Step 5: Eat regular meals, and take your time

For people with sensitive guts, when and how they eat matters almost as much as what they eat. The National Institute for Health and Care Excellence (NICE) guidance on irritable bowel syndrome advises people with IBS to have regular meals and take time to eat, avoid missing meals or leaving long gaps, drink at least 8 cups of fluid a day, restrict tea and coffee to 3 cups a day, and reduce alcohol and fizzy drinks (NICE CG61).

That advice was written for IBS, but it is a useful template for anyone whose gut reacts to stress or irregular routines. Eating at a desk in five minutes, skipping breakfast and then eating a large late meal is a common pattern behind bloating and discomfort. Where IBS symptoms carry on despite regular meals, the next evidence-based step is usually the low FODMAP diet, ideally with a dietitian guiding each phase. It is not a general gut health diet, and it is not meant to be followed long term.

Step 6: Keep alcohol low

Heavy drinking irritates the stomach lining, loosens stools and is linked to a range of digestive diseases. UK low-risk advice is to keep to no more than 14 units a week if you drink regularly, to spread those units across 3 or more days rather than saving them up, and to build several alcohol-free days into each week (NHS). The NHS also notes that there is no completely safe level of drinking.

If you are tracking your gut symptoms, alcohol is one of the first variables worth testing. Many people notice a difference within a couple of weeks of cutting back.

Step 7: Move more

Exercise is good for bowel regularity, and there is early evidence that it changes the gut microbes themselves. In a small study, 32 previously sedentary adults completed 6 weeks of supervised endurance exercise, three times a week, with their diet controlled before each sample (Allen and colleagues, Medicine and Science in Sports and Exercise 2018). Exercise increased short-chain fatty acids in the stools of lean participants but not of those with obesity, and the changes largely reversed once participants returned to a sedentary lifestyle during a 6-week washout.

The message is modest but practical: activity helps, the effect depends on the person, and it lasts only while you keep doing it. Any regular movement you enjoy, from brisk walking to cycling, counts.

Step 8: Review your medicines, especially antibiotics and acid suppressants

Some of the biggest disruptions to gut microbes come from medicines. Antibiotics are the obvious example. They are essential when needed, but the NHS points out that they do not work for viral infections such as colds and flu, and most coughs, and lists diarrhoea and bloating among their common side effects (NHS, antibiotics). The best way to protect your gut is not to ask for antibiotics you do not need, and to take them exactly as prescribed when you do.

Acid-suppressing medicines called proton pump inhibitors (PPIs) are less obvious. A study of 1,815 people across three cohorts found that PPI use was associated with lower microbial diversity and changes in about 20% of bacterial taxa, including more bacteria normally found in the mouth (Imhann and colleagues, Gut 2016). The authors concluded that, at population level, the effects of PPIs on the microbiome were more prominent than those of antibiotics or other commonly used drugs.

That does not mean you should stop a prescribed medicine. PPIs protect people from bleeding, ulcers and serious reflux. It does mean that a long-standing prescription is worth reviewing with your GP or pharmacist, particularly if it was started for a short-term problem years ago.

Step 9: Look after sleep and stress

The gut and brain communicate constantly, which is why stress can trigger diarrhoea, nausea or a loss of appetite, and why many people with IBS notice flare-ups in difficult periods. NICE advises healthcare professionals to encourage people with IBS to make the most of their leisure time and to create relaxation time.

The evidence that better sleep or lower stress improves the microbiome in healthy people is limited, so this step is listed last. But regular sleep, a wind-down routine and some form of relaxation are low-cost and help in other ways. For IBS that has not responded to medicines after 12 months, NICE says referral for psychological interventions such as cognitive behavioural therapy or hypnotherapy should be considered.

Probiotic pills or food first?

Probiotic capsules are the product most people reach for first. The evidence says they should usually come last. Their proven uses are narrow, tied to named strains, with the best results in preventing diarrhoea during antibiotic treatment, and a capsule taken every day by someone with no symptoms has not been shown to do much. Fibre, plant variety and fermented foods, by contrast, feed and diversify the microbes you already have, and they bring other nutrients with them.

Diet quality matters in another direction too. Diets built on heavily processed foods tend to be low in fibre and plant variety. Our guide to ultra-processed foods looks at what the research does and does not show.

A practical way to judge where you stand is our free healthy eating check, which shows how your fibre, fruit and vegetable intake compares with guidelines in a few minutes.

What are the signs of an unhealthy gut?

Online lists of "signs of an unhealthy gut" usually include bloating, wind, irregular bowels, tiredness, skin problems and food cravings. Most of these are common, non-specific and usually harmless. They are poor guides to the state of your microbes, and no stool test sold direct to consumers can diagnose an "unhealthy gut".

What matters more is knowing which symptoms need a doctor rather than a diet change. Among the possible symptoms of bowel cancer, the NHS includes: a change in your poo that is unusual for you, such as looser stools, diarrhoea or constipation; needing to poo more or less often than usual; blood in your poo, which may look red or black; bleeding from your bottom; often feeling you need to poo, even straight after going; tummy pain or a lump; bloating; losing weight without trying; and feeling very tired or short of breath (NHS, bowel cancer symptoms).

Low vitamin levels can also masquerade as gut or energy problems. If you eat little or no animal food, or you take long-term acid suppressants, it is worth reading about vitamin B12 deficiency, which causes tiredness and other symptoms that are easy to blame on digestion.

What is the fastest way to improve gut health?

Your gut microbes respond to diet quickly. In a small study of 10 volunteers who ate an exclusively plant-based or animal-based diet for 5 days, the microbial community shifted within a single day of the animal-based diet reaching the gut, and reverted 2 days after it ended (David and colleagues, Nature 2014).

That speed cuts both ways. Changes appear fast, but they also fade fast, so a 3-day "gut reset" achieves little. The fastest route to lasting change is the least exciting: increase fibre and plant variety this week, keep doing it, and judge the results over about four weeks rather than four days.

When a dietitian can help

Most people can work through these nine steps alone. A registered dietitian is worth seeing if you have IBS or another diagnosed gut condition, if you have tried the basics for a few months without improvement, if you are cutting out whole food groups, or if you have a history of disordered eating. A dietitian can identify what is actually driving your symptoms and build a plan that protects your nutrition while you test changes. To talk your own symptoms through, book a session with a dietitian.