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Your gut and your brain: why your stomach has opinions

By Kerri Hopkins · 5 min read · 20 October 2026

Butterflies, "gut feelings" and the dash to the loo before a big meeting

You have probably felt it: nerves that go straight to your stomach, or a stomach that is off and a mood to match. There is a reason for the saying. Your gut and brain talk to each other all day, in both directions.

What the research says

Researchers describe a two-way link between the gut and the brain. Early studies suggest the balance of bacteria in your gut may be linked to mental wellbeing, but more research is needed before anyone can say how, or promise that a food or supplement will change your mood. So this is a "listen to your body" subject, not a "buy this powder" one.

Stress and your stomach

The NHS lists stomach problems among the physical effects of stress. For irritable bowel syndrome (IBS), the NHS lists stress and anxiety as possible triggers, along with certain foods and drinks. IBS can cause stomach cramps, bloating, diarrhoea or constipation, and flare-ups can come and go, sometimes for no obvious reason.

Food ideas that help most people

• Fibre. Adults are advised to aim for about 30g a day, and most of us average about 20g. Good sources are porridge, wholegrain bread and pasta, brown rice, beans, lentils, chickpeas, vegetables, fruit, and nuts and seeds.
• Variety. Fibre feeds the helpful bacteria in your gut, and different plants provide different kinds. You may have heard you should eat 30 different plants a week. The British Nutrition Foundation says that comes from a study that was only a snapshot. What is supported is five portions of fruit and veg a day plus wholegrains, beans, lentils, nuts and seeds.
• Regular meals. For IBS, the NHS advises not skipping meals or eating too quickly.
• Fluids. For IBS, the NHS suggests at least 8 to 10 drinks a day (about 1.5 litres).
• Caffeine and alcohol. The NHS suggests no more than 3 caffeinated drinks a day with IBS, and not too much alcohol or fizzy drink.
• Fermented foods. Yogurt, kefir and kimchi may contain live bacteria, but they are not always "true probiotics". Look for "live or active cultures" on the label.
• Probiotics. The evidence is strongest for specific conditions, and the strain matters. The NHS says people with IBS can try them for a month.

A food and symptom diary

If your gut is unpredictable, try writing down what you eat and how you feel. The NHS recommends this for IBS. Patterns can be surprising, and the diary gives your GP something to work from. It is a good one for the toolkit too.

Your gut and your iron

Your gut also decides how much iron and other nutrients you take in. Blood loss from the gut can be a cause of iron deficiency, which is why a FIT test (to look for hidden blood in your poo) is sometimes used. Conditions such as coeliac disease can lead to low iron and tiredness too. If you have been tired for a long time, it is worth asking about your gut as well as your iron.

One for coeliac disease

If you think you may have coeliac disease, do not cut out gluten yet. The NHS says to keep eating gluten until you have had the blood test, because avoiding it can give an inaccurate result.

When to see your GP

Please see your GP if you have any of these, even if you think it is "just IBS":

• blood in your poo, which may look red or black
• a change in your bowel habit that is not usual for you, such as softer poo, diarrhoea or constipation
• losing weight without trying
• feeling very tired or short of breath
• symptoms that do not improve with changes to your diet

Call NHS 111 or get an urgent appointment if your poo is black or dark red, or you have bloody diarrhoea. Call 999 or go to A&E if you are bleeding non-stop or there is a lot of blood.

Sources

NHS: IBS symptoms · NHS: IBS diet, lifestyle and medicines · NHS: How to get more fibre · NHS: Bowel cancer symptoms · NHS: Coeliac disease diagnosis · NHS: Iron deficiency anaemia · British Nutrition Foundation: Gut health

BioHer provides educational information only. It is not medical advice, diagnosis or treatment, and it does not replace your GP or other healthcare professional. If symptoms feel urgent or severe, call 111 for urgent advice, or 999 in an emergency.