Finding Relief – Can Diet Improve Constipation?

Constipation affects around 5-15% of people worldwide and can can happen for a number of reasons. Changes in your normal routine (like travel or illness), low fibre and water intake, and low levels of physical activity can all affect bowel function.

Certain medications may also contribute, like iron supplements, some pain medications, diuretics, and medications used to manage heart conditions, allergies or mental health conditions. If you think a medication is affecting your bowels, speak with your GP or pharmacist rather than stopping it yourself.

How do you know you’re constipated?

Constipation is not only about how often you go to the toilet, but also about the consistency. Common signs include:

• Passing hard or lumpy stools (a 1 or 2 on the Bristol Stool Chart)
• Straining to open your bowels
• Feeling as though your bowels have not emptied completely
• Feeling as though there is a blockage
• Needing to change your position on the toilet to pass a bowel motion
• Having fewer than three bowel motions per week

If you regularly experience two or more of these symptoms for at least three months, speak with your GP. They can help identify whether you have chronic constipation and check for any underlying causes.

What can you try?

New evidence-based guidelines from the British Dietetic Association have identified several dietary strategies that may help adults manage chronic constipation. Researchers reviewed 75 clinical trials to identify the foods and supplements with the strongest evidence.

You do not need to try everything at once - choose one and trial it consistently. Making several changes at once may increase bloating or diarrhoea and makes it hard to know what has helped.

You may find it helpful to keep a written record of your bowel frequency, stool consistency, straining and any other variables like stress, activity, or food intake. If one strategy does not provide a meaningful improvement after a few weeks, consider another option or seek individual advice from a GP or dietitian.

1. Psyllium

Psyllium is the most researched fibre supplement. It is a soluble, viscous fibre that dissolves in water and thickens to form a soft gel within the bowel. This helps to soften stools and make them easier to pass.

Research suggests that psyllium can increase bowel frequency, improve stool consistency and reduce straining. Although the overall quality of the research is considered low, it is still strongly recommended because the benefits appear meaningful and it is generally affordable, accessible and safe when used correctly. Since psyllium absorbs water, it should always be taken with extra fluids.

The guidelines suggest that more than 10 g per day may provide the greatest benefit. Start with a smaller amount and gradually increase it over several weeks. Some people experience bloating or wind when they first begin taking it, particularly if the amount is increased too quickly.

You can add psyllium to drinks, smoothies, or bircher muesli.

2. Kiwifruit

Try eating two kiwifruit each day for at least four weeks.

Research suggests that kiwifruit can improve bowel frequency and may work as well as psyllium for providing overall constipation relief. It may also cause less bloating, abdominal pain and wind, making it a good first option for people with sensitive bowels. Kiwifruit can increase the amount of water held within the bowel and add bulk to stools, helping them become softer and easier to pass.

Enjoy them on their own, or with Greek yogurt and granola, in a parfait, or on top of overnight oats.

3. Prunes

Clinical studies show that prunes are just as effective as some fibre supplements in managing constipation. As a stone fruit, prunes (dried plums) contain both fibre and a naturally occurring carbohydrate called sorbitol that helps draw water into the bowel making stools easier to pass through.

Try them in homemade snacks like Clare's Muesli Chews, chopped up over breakfast cereal or yoghurt, or added to a fruit crumble.

If you don’t like prunes, other foods that contain sorbitol include apples, pears, cherries, apricots, plums and “sugar-free” chewing gum and “sugar-free” lollies.

4. Magnesium Oxide

One of the most effective supplements identified in the guidelines is magnesium oxide. It works to improve stool frequency and consistency by helping to draw water into the bowel, making stools softer and easier to pass.

If you have any other health condition like heart disease or kidney disease, talk to your GP or your dietitian before you start taking a supplement like magnesium oxide.

5. Fluids

Drinking enough water is particularly important when increasing fibre or using fibre supplements. When your body is a bit dehydrated, there’s less water for the fibre in your colon to absorb, meaning your bowel motions also become dehydrated and harder to pass.

If your urine is a pale yellow colour (or the colour of straw) – it’s usually a good indicator that you’re drinking enough water.

What about a high-fibre diet?

There is currently not enough research to conclude that general advice to “eat more fibre” will treat chronic constipation on its own. However, high-fibre foods like wholegrains, legumes, fruit, vegetables, nuts and seeds all remain an important part of a healthy diet and support long-term gut and overall health. Different types of dietary fibres improve bowel function through different processes.

• Fermentation of fibre in the colon produces water and other molecules, which make stools softer and easier to pass.
• Absorption of water into stools stimulates the gut to contract and makes bowel motions softer.
• Higher fibre intake creates bigger stools, which pass more quickly, resulting in more regular bowel motions.

Examples of good sources of fibre include;

Use our Healthy Gut recipe filter for high fibre meal and snack ideas.

When should you seek medical advice?

Speak with your GP if your constipation lasts more than two to three weeks or you notice a sudden or unexplained change in your regular bowel habits.

Seek prompt medical attention if you also experience:

• Severe or worsening abdominal pain
• Vomiting or a swollen abdomen
• An inability to pass stools or wind
• Blood in your stool
• Unexplained weight loss
• Fever or significant illness

Want to dive deeper into the research?

Listen to the Nutrition Science Bites episode with Professor Clare Collins and Professor Kevin Whelan from King's College London and discover the evidence behind how certain foods can help prevent and relieve constipation.

Kevin is a Principle Investigator leading a translational research program exploring the interaction between diet and the gut microbiome in health and disease.

🎧 Listen now: Yes - specific foods can help prevent and treat constipation! Here's what the research evidence tells us! ...with Professor Kevin Whelan