How Does Fibre Affect IBS?

Introduction

Do you find that fibre makes your IBS symptoms worse?

You may have been told by your doctor to eat more fibre, but you will probably find that this can worsen your symptoms.

So what are you supposed to do? Avoid fibre? Eat an unhealthy diet to save your IBS? You may be confused as to why your doctor has given you this advice and yet it has not worked. Perhaps you are not ‘doing it right.’ Or maybe you are having too much fibre?

In this article, I will explain to you why fibre makes IBS symptoms worse. And, what type of fibre you can have safely to ensure your diet is healthy without IBS symptoms.

How Much Fibre Should I Eat For IBS?

Whilst we know that fibre helps to regulate our bowels, it can also trigger IBS symptoms

There is currently no evidence to support a specific level of fibre for those with IBS. So, I always recommend that you aim for the same as the general population: 30g /day (1 , 2).

Should I Follow a Low Fibre Diet for IBS?

It can be easy to think that you should just avoid all fibre to help your IBS. But, please do not avoid all fibre!

Fibre provides many benefits for your gut health such as bulking your stool and improving the time it takes to move through your gut. Fibre also produces by-products when it is broken down by bacteria in your large bowel. These by-products affect your gut microbiota, immune system and neuroendocrine system (4). It has also been linked to a reduce risk of colon cancer (3).

In addition to gut health, eating 30g of fibre a day has been shown to reduce your risk of conditions such as heart disease and diabetes (3).

So, continue to eat a good level of fibre if you are doing so already. If you are not, increase to 30g / day. Just make sure you do this slowly to allow your gut time to adjust. It is also important to ensure that you drink enough fluid.

What Types of Fibre Are Good For IBS?

You may have been told to increase your soluble fibre intake. But this is no longer accurate advice.

Fibre used to be split simply into 2 groups: soluble and non-soluble. However, we now know that within these groups, there are huge varieties of fibre types. Each type of fibre will provide different benefits and affects to the body.

For example, oligosaccharides are a type of short-chain, soluble, fermentable carbohydrate. These can be broken down by your gut bacteria, creating gas (4). So, typically not good for those with IBS.

Compare this to long-chain, intermediate viscous, soluble and moderately fermentable fibre such as psyllium. This fibre has only a very small gas production (4).

Ispaghula Husk / Psyllium

This fibre is good for those with mild / moderate IBS constipation predominant. It is recommended that you start using this fibre from a low dose and work your way up slowly (5).

Ispaghula husk has been shown to improve IBS symptoms more than a placebo supplement (4). 4g of psyllium a day for 12 weeks has been shown to significantly reduce symptom severity in IBS (6).

Linseed / Flaxseed

Both ground and whole linseed (flaxseed) are good for those with IBS – C. Studies show that take 6-25g/day can help with constipation, abdominal discomfort and bloating over 3 months (9).
You should start with 4-12g/day and work your way up to 25g/day (1 tablespoon – 12g) (2).

Linseed works by absorbing fluid to create a gel. It is therefore important that you take 100mls of fluid with each tablespoon of linseed (7). Please note, it may take up to 6 months to see a benefit in your symptoms (2).

Wheat Bran

I would advise against using wheat bran as a supplement for IBS. In one study, it was shown to have no benefit and in another, it was shown to worsen IBS pain (6, 8).

As per the British Dietetic Association advice, do not increase your wheat bran intake above your normal day to day diet (2).

Should I Take Fibre Supplements For IBS?

The idea of being able to take and dietary supplement to solve a medical problem is amazing. It is easier than changing your diet which means that you will feel it is more achievable. But, do not jump to supplements straight away.

Can Fibre Make IBS Worse?

Fibre will not make IBS ‘worse.’ But, certain types of fibre or quantities may flare up symptoms. Everyone has different tolerance levels and it is important to find out yours.

FODMAPs – fermentable oligosaccharides, disaccharides, monosaccharides and polyols cause bloating, diarrhoea and stomach pain in those who have IBS. You can work through the low FODMAP diet process to pin-point which ones cause your symptoms and how much of them you can tolerate.

Take Home Message

Even if you have IBS, you should aim for 30g of fibre a day. However, where that fibre comes from is important. A diet high in FODMAPs can worsen symptoms, whilst other dietary fibre may help IBS symptoms.