Fibre and water: the two pillars of a happy gut
Fibre gives stool bulk and feeds your gut bacteria; water keeps it soft. Most of us fall short on both.
The targets
UK guidance is 30g of fibre a day for adults, and NHS bowel services suggest at least 1.5 litres (6–8 cups) of fluid. Most adults average around 20g of fibre, so there’s usually room to improve.
Soluble vs insoluble fibre
Soluble fibre (oats, fruit, vegetables, pulses) forms a soft gel and is usually gentler on bloating. Insoluble fibre (wheat bran, wholegrain skins) adds bulk. If you get bloated or constipated easily, favour fruit and vegetables over bran.
Easy swaps for +10g a day
- White bread → wholemeal or seeded bread
- Sugary cereal → porridge with berries
- Add a handful of lentils, beans or chickpeas to soups and sauces
- Keep the skins on potatoes
- Snack on fruit, carrot sticks, nuts or seeds
Go slowly
Increasing fibre too fast causes wind and bloating. Add a little each week and drink more alongside it. Too much fibre can even loosen stools — the goal is the Type 3–4 sweet spot.
Your gut bacteria love it
Gut microbes ferment fibre into short-chain fatty acids such as butyrate, which fuel the cells lining your colon. Eating a wide variety of plants is linked with a more diverse microbiome. Fermented foods such as live yoghurt and kefir are a bonus — most healthy people don’t need a daily probiotic tablet.
Cut back on ultra-processed food
Foods packed with sweeteners, emulsifiers and additives are often low in fibre and may irritate the bowel. Cooking from simple ingredients more often is one of the best things you can do for your gut.
Frequently asked questions
How much fibre should I eat a day in the UK?
Adults are advised to eat 30g of fibre a day from fruit, vegetables, wholegrains, pulses, nuts and seeds.
How much water helps constipation?
NHS bowel services suggest at least 1.5 litres (6–8 cups) of fluid a day unless your doctor advises otherwise.
Sources
This guide is for general education and is not a substitute for advice from your doctor. If you are worried about symptoms, contact your GP or NHS 111.