Photo of different kinds of food that contain the two types of fibre, soluble and insoluble

Fibre for Gut Health: Understanding Soluble and Insoluble Fibre

Fibre is essential for gut health, but not all fibre works in the same way. The two main types are soluble fibre and insoluble fibre. Soluble fibre absorbs water and forms a gentle gel-like substance that can support digestive comfort, while insoluble fibre adds bulk to stools and helps maintain regular bowel movements. Understanding the difference can help you choose the right foods for your digestive health.

Many people are trying to improve their gut health by increasing their fibre intake.

But what often surprises my clients is that not all fibre behaves in the same way.

Some fibres can help support bowel regularity, beneficial gut bacteria and digestive comfort. Others may aggravate symptoms when the gut is already inflamed or sensitive.

As a nutritional therapist specialising in gut health, I find few people understand the important differences between soluble and insoluble fibre.

There is far more to fibre than simply “roughage”.

Let’s explore why the type of fibre you choose can really matter, especially if you struggle with IBS, IBD, bloating, constipation, diarrhoea or a sensitive digestive system.

Why Fibre Is Important for Gut Health

Most people think of fibre as something we need simply to encourage bowel movements and avoid constipation.

And yes, fibre does help support bowel regularity. But it is more complex than that.

Fibre also plays an important role in feeding beneficial gut bacteria and supporting a healthy gut microbiome.

A more balanced microbiome is important for digestive health, immune health and overall wellbeing. If you want to know more about your microbiome and gut health you may find this helpful: How to Transform Your Gut Health

The two main types of fibre are:

Soluble fibre
Insoluble fibre

Both are important.

But they can affect the digestive tract very differently.

One type may be more aggravating to the gut barrier if inflammation is present, while another can have a gentler, more soothing effect and may help in situations like diarrhoea.

This is why understanding fibre types can be so helpful.

What Is Inflammatory Bowel Disease (IBD)?

Although this article is mainly about fibre for gut health, it’s important to understand why fibre type matters so much for people with more sensitive or inflamed digestive systems.

Inflammatory bowel disease, often shortened to IBD, is a term used to describe chronic inflammation of the gastrointestinal tract.

It usually goes through periods of flare-ups and remission.

There are two main types:

Ulcerative colitis

This involves inflammation and sores, or ulcers, in the large intestine, starting from the rectum and travelling backwards through the colon.

Crohn’s disease

This can involve inflammation anywhere along the digestive tract, although it is often found where the small intestine joins the large intestine. It can also involve deeper layers of the gut lining.

Whilst the exact cause of IBD is unknown, it is strongly linked to an impaired immune system that responds incorrectly to a trigger such as a virus or bacteria. This may cause immune cells to attack the gut tissues, resulting in chronic inflammation.

There also appears to be a genetic component, as IBD can run along family lines.

IBD is different from IBS.

IBS, or irritable bowel syndrome, is not considered as serious as IBD, but it can still make life extremely difficult for sufferers, affecting social life, work, confidence and daily routines.

Key IBD Symptoms to Watch Out For

Please don’t panic, as some of these symptoms may also occur with IBS.

However, if you are concerned, it is important to speak to your medical provider.

Symptoms to watch out for include:

prolonged diarrhoea, with or without urgency
abdominal pain or cramping
blood in the stools
unexpected weight loss
unexplained fatigue

If you have any concerns, do consult your medical provider. They may run a stool test to check for raised calprotectin, which can indicate inflammation, and faecal blood. If necessary, they may arrange a colonoscopy.

Why Different Types of Fibre Matter

Concerned about IBS or IBD Know your fibre to help manage your symptoms (1)

The way fibre behaves in the gut can make a big difference.

For a calm, healthy gut, increasing fibre can often be very supportive.

But if the gut is inflamed, irritated or already struggling, some forms of fibre may be harder to tolerate.

This is why I often encourage clients to stop thinking of fibre as one single thing.

It is not just about eating “more fibre”.

It is about understanding which type of fibre may suit your gut at a particular time.

Insoluble Fibre: Benefits and When It May Irritate the Gut

Insoluble fibre is otherwise known as “roughage”.

It is the fibre that adds bulk to stools.

It does not dissolve in water and can have an almost abrasive-like effect on the gut wall as it passes through. Roughage is a good word to describe it.

For a healthy gut, insoluble fibre is necessary. It helps to keep bowel transit time regular and can help avoid constipation, where transit and bowel regularity are too slow.

It is also excellent fuel for beneficial gut bacteria, helping to keep the microbiome in balance.

So, insoluble fibre is necessary and excellent for the gut when the gut is calm and in balance.

But it can be a “no, no” if the gut is already inflamed during IBD flare-ups, as this type of fibre may irritate the gut lining.

Foods High in Insoluble Fibre

Insoluble fibre is the rigid fibre found in certain plant foods.

The outer cell walls of some plants are tough, so they may aggravate and irritate an already inflamed gastrointestinal tract.

Sources include:

woody stems, such as kale, broccoli and artichokes
skins, such as tomato, grape, potato, apple and pear skins
whole nuts and seeds
pulses, such as chickpeas, kidney beans and lentils
pips and seeds found in tomatoes
whole flaxseed and sesame seeds
watermelon seeds
stringy fibres found in some beans and celery
cabbage
onions
sweetcorn

Wholegrains containing the tough outer husk, where the bran is found, are another source of insoluble fibre. This includes foods such as wholegrain bread, rice and pasta.

Soluble Fibre: The Gentler Fibre for Sensitive Digestion

Soluble fibre is much softer.

It absorbs water as it passes through the digestive tract, creating a gel-like substance.

This can be gentler on the digestive system.

It helps keep stools soft, which can support bowel regularity and constipation, yet it does not usually cause stools to become too loose. This means it can also have a positive effect in situations like diarrhoea.

Soluble fibre also provides fuel to support the growth of beneficial gut bacteria.

This is why soluble fibre may be better tolerated during IBD flare-ups, while insoluble fibre may not be.

Foods High in Soluble Fibre

Sources of soluble fibre include:

apple pectin from stewed peeled apples with cinnamon and no sugar
avocado
skinless apricots
cooked rolled oats in water or nut milk, not dairy
sweet potato, mashed and without the skin
milled ground flaxseed

Apple pectin, from stewed peeled apples with cinnamon and no sugar, can have an anti-inflammatory effect as well as being gentle on the gut wall.

This is usually well tolerated during flare-ups.

You may also enjoy reading: Why I recommend stewed apple for gut health or Growing your own vegetables: Gardening Health Benefits

Can Supplements Support Digestive Health?

There are some natural supplements that may be helpful for both IBD and IBS.

Professional advice is recommended, especially if you have a diagnosed inflammatory bowel condition or are taking medication.

Psyllium husk

Psyllium husk is a natural soluble fibre.

It is gentle on the gut wall and may support and regulate bowel movements.

Deglycyrrhizinated liquorice

Deglycyrrhizinated liquorice, often called DGL, has a soothing effect on the upper gastrointestinal tract.

It has been researched and shown to be an effective approach for ulcers of the gastrointestinal tract.

Slippery elm

Slippery elm has a soothing, calming effect on an inflamed gut lining.

This soothing action can be attributed to its antioxidant action and mucilage, which coats, soothes and calms the intestinal lining.

Can Fibre Help IBS Symptoms?

Many people with IBS find that certain types of fibre are better tolerated than others.

This is where understanding soluble and insoluble fibre can be useful.

For example, someone with a more sensitive gut may find large amounts of roughage aggravating, especially if they are already bloated, uncomfortable or experiencing loose stools. Others may need more fibre to support constipation and bowel regularity.

The important point is that there is no one-size-fits-all approach.

If bloating and digestive symptoms are ongoing, you may find this helpful: Food elimination and bloating

You may also want to read: Is FODMAP good for your gut health?

Supporting Your Gut Microbiome Long-Term

Fibre is one of the most important fuels for the gut microbiome.

The aim, when your gut is calm enough, is to gradually build diversity. This means increasing the range of plant foods you tolerate over time. That does not mean forcing in lots of raw vegetables, bran or beans if your gut is already inflamed or struggling. It means working with your digestive system.

For some people, that starts with gentle soluble fibre. For others, it may mean slowly increasing a wider range of fibre-rich foods once symptoms have settled.

The goal is a more balanced, resilient gut microbiome.

You may find this useful too: How to transform your gut health

Final Thought

If you’ve been trying to improve your gut health by simply eating more fibre, but your symptoms are not improving, you’re not alone.

Many people are told to “eat more fibre”, but they are rarely told which type of fibre may suit their gut best. And that distinction can really matter.

Soluble fibre and insoluble fibre both have important roles, but your gut may need different support depending on whether it is calm, constipated, irritated, inflamed or sensitive.

If you suffer from symptoms you can’t resolve, or you are unsure about your diet and health, you are very welcome to book a free discovery call.

We can simply talk through what is going on and what may help support your digestion in a calm, practical and personalised way.

Caroline x

Gut Health Nutritionist Caroline Peyton Principles — Caroline is a Professional Nutritionist, Naturopath based in Wiltshire.

FAQs

What is the difference between soluble and insoluble fibre?

Soluble fibre absorbs water and forms a gel-like substance, while insoluble fibre adds bulk to stools and helps support bowel movements.

Which fibre is best for gut health?

Both soluble and insoluble fibre play important roles in gut health. The right balance depends on your digestive health and individual symptoms.

Can fibre help IBS symptoms?

Many people with IBS find that certain types of fibre are better tolerated than others. Understanding the difference between soluble and insoluble fibre can be helpful.

What foods contain soluble fibre?

Examples include stewed apples, avocado, oats, sweet potato and ground flaxseed.

What foods contain insoluble fibre?

Examples include wholegrains, nuts, seeds, pulses, broccoli, cabbage and fruit skins.

Can you eat fibre during an IBD flare-up?

Some soluble fibre may be tolerated during an IBD flare-up, while insoluble fibre may aggravate an inflamed gut. Always seek medical advice if symptoms are severe or ongoing.

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