Constipation and Fibre: What You Need to Know
By Dr Timothy Eden, MBBS
Registered Dietitian from Eden Health and Nutrition
Read time approx. 4mins
Constipation is one of the most common gut problems we see in the UK, affecting around 1 in 7 adults and up to 1 in 3 children at any given time (1). It usually means having fewer than three bowel movements a week, straining to pass stools or feeling that you haven’t completely emptied your bowels. While it can be an occasional nuisance for many people, persistent constipation can cause discomfort and have a big impact on day-to-day life and is a common reason why people seek input from their GP or dietitians.
Why is constipation so common?
There are lots of reasons why constipation is common in the UK. Our diets are often higher in ultra-processed foods (UPFs) and lower in whole, fibre-rich foods than in previous generations. UPFs, such as many ready meals, snacks and takeaways, tend to be low in fibre. Busy lifestyles and eating on the go can also make it harder to get enough fibre every day.
Some groups of people are more at risk:
Older adults – as we age, the nerve signals to our gut become less effective, slowing gut movement.
People taking certain medications – opioid painkillers (like codeine or morphine), some antidepressants, and iron tablets can all make you constipated.
People who drink little fluid or who are less mobile – staying hydrated and active helps to keep things moving.
People with known health conditions may also be more prone such as irritable bowel syndrome (IBS), haemorrhoids, functional pelvic floor conditions, hypothyroidism and hormonal changes in pregnancy and post-partum.
Hydration and lifestyle factors
Dehydration can also make constipation worse. Most adults should aim for 25–30ml of fluid per kg of body weight each day (2). For someone weighing 70kg, that’s roughly 1.8–2.1 litres of fluid daily. Water is best but tea, coffee, milk and sugar-free squash all count. Regular movement and exercise even gentle walking can also help your gut work more effectively.
Fibre: soluble vs insoluble
Fibre plays a key role in preventing and easing constipation. There are two main types:
Insoluble fibre adds bulk to stools and helps food move through the gut more quickly. You’ll find this in wholegrains (wholemeal bread, brown rice), wheat bran, nuts and seeds.
Soluble fibre absorbs water and forms a soft gel, which can make stools easier to pass. Foods rich in soluble fibre include oats, apples, pears, beans and lentils.
A mixture of both types works best. Kiwi fruit is a great example – it contains both soluble and insoluble fibre as well as an enzyme called actinidin which may help digestion and improve gut motility/movement (3).
How much fibre do we need?
The UK guidelines recommend adults aim for 30g of fibre a day (4). Most people only manage around 20g, so there is normally room for improvement. Getting enough fibre helps with constipation and also reduces the risk of heart disease, type 2 diabetes and bowel cancer.
Tips to increase fibre
Start your day with porridge oats, which are high in soluble fibre.
Add a portion of fruit such as kiwi, prunes or berries. Prunes also contain sorbitol, which draws water into the bowel and softens stools.
Eat at least five portions of fruit and veg daily.
Swap white bread, rice and pasta for wholegrain versions.
Add beans, lentils or chickpeas to soups, casseroles and salads.
Try a small glass (150ml) of prune juice if you’re struggling.
Important: Build up fibre slowly and drink plenty of fluid, otherwise you may feel bloated or uncomfortable.
When to speak to a doctor or pharmacist
See a healthcare professional if you notice:
Blood or mucus in your stool
Unexplained weight loss
A persistent change in your bowel habit
Severe or ongoing constipation that doesn’t get better with diet and lifestyle changes
These symptoms can sometimes point to a more serious underlying problem and should always be checked.
What about laxatives?
If diet and lifestyle changes aren’t enough; your GP or pharmacist might recommend a laxative. Different types work in different ways:
Stimulant laxatives (e.g. senna, bisacodyl) help the bowel muscles to contract.
Osmotic laxatives (e.g. macrogol/Movicol, lactulose) draw water into the bowel to soften stools.
Stool softeners (e.g. docusate sodium) make stools easier to pass.
It’s always best to get advice before starting a laxative so you know which type is right for you and how long you should take it for.
The bigger picture
Fibre is not only essential for easing constipation but it’s also beneficial for your gut bacteria, heart health and blood sugar levels. But don’t forget that hydration, movement and reviewing your medications are just as important.
If you’re struggling with constipation, start with small changes, add more fibre-rich foods gradually and speak to your GP or healthcare professional if things don’t improve.
References
NHS. Constipation. Available at: https://www.nhs.uk/conditions/constipation (Accessed July 2025)
NHS Eatwell Guide. Available at: https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/the-eatwell-guide (Accessed July 2025)
Chang CC et al. Kiwi fruit improves bowel function in adults with constipation. Asia Pac J Clin Nutr. 2010;19(1):91–98.
Scientific Advisory Committee on Nutrition (SACN). Carbohydrates and Health. 2015. Public Health England.