What to eat (and take) for constipation, based on new guidelines

What is constipation? 

Most of us think of constipation as not pooing very often, or less often than is normal for us. Medically, it’s usually defined as pooing fewer than three times a week. But constipation isn’t just about frequency. Other common symptoms include: 

• Straining or pain when pooing 
• Poo that is lumpy / hard  
• A sense of not having completely emptied your bowels after a poo  
• Sensation of obstruction or blockage 
• Tummy ache and bloating  

Constipation can be a side effect of certain medications and health conditions, but for many people there’s no obvious cause. When symptoms last for a long time, it’s known as chronic constipation, which affects around 1 in 10 people worldwide. 

Can diet help?

Research shows that around 98% of people with constipation use some form of treatment, with most preferring dietary approaches over medication. Until recently, though, dietary advice has been a bit vague. Things like “drink more water” or “eat more fibre” are often recommended, without much evidence to support them. 

That’s now changed. A team of UK-based clinicians has published the first dietary guidelines for managing chronic constipation in adults. They reviewed evidence from 75 randomised controlled trials, looking at how different dietary interventions affect constipation, before developing a set of recommendations. 

Here’s what they found:  

Foods that help

Kiwi fruit  

Eating two to three kiwi fruits a day can help ease some symptoms of constipation. In studies, kiwi was found to be as effective as psyllium, but many people may find the kiwi option easier and more enjoyable. 

Kiwis are rich in water-holding fibre, which helps soften poo and make it easier to pass. Both green and gold kiwi have been shown to work. In the studies, people ate them without the skin, but keeping the skin on will add a bit of extra fibre. Just be aware that increasing fibre quickly can lead to more wind for some people. 

Kiwi is also low FODMAP, making it a good option if you have constipation-predominant IBS. 

Prunes  

Prunes have also been compared with psyllium and kiwi and shown to be similarly effective. They contain a natural sugar alcohol called sorbitol, which helps draw water into the bowel and soften stools. 

Because sorbitol is a FODMAP, prunes aren’t the best choice if you have IBS and are sensitive to FODMAPs. But if you tolerate them well, around eight to ten prunes a day seems to be the effective amount. Start with half that amount and build upwards, adding to porridge, cereal or yoghurt. 

Rye bread  

Replacing white bread with rye bread for at least three weeks was found to increase poo frequency. However, the amount used in studies was quite high, around six to eight slices a day, which isn't realistic for most people.  

You could try a practical approach swapping any white bread at breakfast or lunch for rye and seeing how your symptoms respond.  

Supplements that can help 

Fibre supplements 

Some fibre supplements were shown to soften poo and increase how often people with constipation poo. Of these, psyllium husk, also known as ispaghula, showed the strongest benefits.  

Psyllium husk comes from the husk of seeds from Plantago ovata plants. It’s rich in soluble fibre (which draws in water, softening and bulking out poo). A dose of 10 grams+ per day was optimal, but it makes sense to work up to this if you’re not currently consuming much fibre.  

Psyllium husk can be purchased as flakes, as a powder or or capsules. It can be stirred into porridge or added to a smoothie. Or you can stir into a glass of water or squash (cold is best!) to drink - just do so quickly, as if you leave it, it will turn into a gel.

It’s very important to drink extra fluid when taking psyllium. It needs water to work properly, and without enough fluid it could make constipation worse. This paper recommends around 250 ml of fluid (about a mugful) for every 10 g dose of psyllium. 

Psyllium is usually well tolerated by people with IBS, but it’s still best to start with a small amount and slowly increase the dose.  

Magnesium supplements  

Magnesium oxide is a form of magnesium that draws water into the gut, giving it a laxative effect. Studies found that magnesium oxide supplements increased poo frequency and helped soften stools. 

The recommended dose is between 0.5 and 1.5 g per day for at least four weeks, starting at the lower dose of 0.5 g per day and increasing if needed. 

Probiotics 

Some, but not all, probiotic strains were found to improve certain symptoms of constipation. This fits with existing research showing that probiotic benefits are strain specific, rather than a general effect of all probiotics. 

This chart shows probiotic strains that currently have evidence for helping with constipation. If you decide to try a probiotic, use it consistently for at least four weeks to see whether it’s helpful for you. 

What there wasn’t enough evidence for  

We often hear the advice to “eat more fibre” if you’re constipated. Interestingly, the guidelines found there wasn’t enough strong evidence to recommend this approach this time. This doesn’t mean fibre isn’t helpful - the foods found to be helpful are all rich in fibre. It simply means there aren’t enough high-quality studies looking at the effects of a whole, high-fibre diet on constipation to draw conclusions. 

It’s worth remembering that there is still good evidence that fibre supports gut health overall though.  

The authors also note that the overall quality of evidence was low, and more research is needed. Even so, these guidelines offer a helpful starting point for where to focus your efforts, especially if you’re thinking about dietary changes or trying supplements.