Dietary fibre is a crucial component of a healthy diet, with significant effects on digestive health. It helps us maintain regular bowel movements and can help to prevent constipation, but its impact goes far beyond just keeping things moving.
Ensuring enough dietary fibre in our diet can keep our gut microbiome healthy, which has been show to have impacts on our cardiovascular health, our cognition, memory and brain function, our reproductive health, our bone health, and can reduce our risk of many common conditions such as type 2 diabetes, cardiovascular disease and certain types of cancer.
The reality is though, most people don’t eat enough. The most recent research done by the UK’s National Diet and Nutrition Survey showed the average person is getting only 18g of fibre per day, far below the minimum recommendation of 30g.
As a country, it is important we begin to prioritise the consumption of fibre, not just to help us prevent gastrointestinal distress, but to keep us healthy in the long term.
Today, we are going to be talking about the types of dietary fibre you can find within your diet, as well as how to prioritise getting more into your meals.
There are Two Main Types of Dietary Fibre
- Soluble Fibre
- Insoluble Fibre
Both types of fibre play important roles, but they have different effects on digestion, and each interacts with gut health in unique ways.
1. Soluble Fibre
What It Is
Soluble fibre has the unique ability of dissolving in water. Here, it creates a gel like substance, which we can use to our advantage.
How It Affects Digestion
Soluble fibre’s unique property of absorbing water can be beneficial for all types of bowel habit complaint. It can absorb the excess water if you struggle with loose stools, and so can thicken them up and make them less urgent and liquid. It can also soften harder stools, if taken with enough water, which can help relieve the symptoms of constipation.
Soluble fibre is also considered a powerhouse of nutrition for your gut bacteria. Therefore, a diet higher in soluble fibre can give your gut microbiome much needed fuel, which can allow a healthier and more diverse microbiome to grow. Not only this, but the digestion of soluble fibres by your gut microbiome also leads to the production of compounds called short chain fatty acids (SCFA’s), such as butyrate and propionate. It is believed that these compounds are one of the reasons having a healthier gut microbiome improves the health of the whole body, and not just the gut.
Foods Rich in Soluble Fibre:
- Oats and oat bran, wheat, rye
- Kiwis, apples, citrus fruits, and berries
- Onion, garlic, carrots and sweet potatoes
- Chickpeas, lentils, tofu, tempeh
- Psyllium husk, chia seeds and flaxseeds
There are Different Types of Soluble Fibre
We can further categorise types of soluble fibre into fermentable and less-fermentable. Whilst all types of soluble fibre are good for gut health, some may cause uncomfortable and difficult to manage symptoms such as gas and bloating.
- Highly fermentable soluble fibre- These are typically known as FODMAP’s and, if you are someone who struggles with gas and bloating, may be making your symptoms worse. Whilst not all FODMAP’s fall into this category, many FODMAP’s which are the most common culprit of symptoms do. These include onion, garlic, and gluten-containing grains such as wheat and rye. If you experience bloating, and have no other conditions which could cause it, you may wish to consider removing these foods from your diet and seeing if this improves bloat and gas symptoms.
- Less fermentable soluble fibre- These soluble fibres are still fermented, but at a much slower and lower rate. Because of this, the bloating and gas symptoms are less prominent, although still may be present if you are particularly sensitive. You may wish to consider speaking to an IBS dietitian if this affects you.
2. Insoluble Fibre
What It Is
Insoluble fibre does not dissolve in water. It adds bulk to the stool and, because this additional bulk stimulates the intestinal muscles to contract, it helps food move more quickly through the digestive system. This is particularly helpful in those who struggle with slow-transit constipation.
How It Affects Digestion
You may have heard this type of fibre be called “roughage” in the past. This slightly outdated term is used because insoluble fibre is typically seen as rough as it doesn’t dissolve in water, and is rather substantial in nature.
As mentioned before, the primary benefit of insoluble fibre is to keep food moving at an appropriate speed through the GI tract. Those who experience constipation will often be recommended to increase the amount of insoluble fibre they eat, as this can help stimulate the bowel.
Secondary benefits of insoluble fibre is that it can relieve the pain that constipation can bring, alongside reducing the risk of haemorrhoids or diverticular disease developing.
Whilst it is not necessarily as nutritionally beneficial for our gut microbiome as soluble fibre is, it still plays an important role in gut health.
Foods Rich in Insoluble Fibre:
- Brown bread, pasta, rice and other ancient grains.
- Wholegrain cereals such as bran flakes or all bran.
- Vegetables with skins, stalks, pips, or seeds, such as kale, broccoli, carrots, celery tomatoes or green beans.
- Fruits with stems, stalks, pips or seeds, such as rhubarb, raspberries or apples.
- Nuts and seeds.
There are Different Types of Insoluble Fibre
Like soluble fibre, there are different types of insoluble fibre; those which are fermentable, and those which are non-fermentable. You may wish to choose different ones depending on whether you experience gas and bloating.
- Fermentable insoluble fibre- These are foods which, again, are high in fibre but also high in FODMAPs. These typically include gluten containing grains, high FODMAP fruits such as dried fruits and tinned pineapple, high FODMAP vegetables such as broccoli stems and corn-on-the-cob, alongside unprocessed bran.
- Non-fermentable/ less fermentable insoluble fibre- These are foods which are less fermentable, and therefore are less likely to cause gas and bloating. They also include certain laxatives, such as methylcellulose.
3. The Role of Fibre in Managing Gastrointestinal Symptoms
Constipation
Constipation is a common digestive complaint, and fibre plays a central role in alleviating it. Insoluble fibre, due to its bulk-forming properties, is particularly effective in promoting regular bowel movements as it speeds up gut transit. It is also recommended to add more soluble fibre to the diet if struggling with constipation, as, when consumed with sufficient water, it can also help by softening the stool and easing its passage. This can reduce need for straining which can lead to haemorrhoids and diverticular pouches being formed.
Diarrhoea
When it comes to managing diarrhoea, soluble fibre is the key player. It helps to absorb excess water in the intestines which leads to the firming up of the stool. Soluble fibre can be particularly beneficial for individuals with irritable bowel syndrome (IBS) or other conditions that cause chronic diarrhoea.
It is important to note, that those with diarrhoea should reduce or not increase their insoluble fibre intake. This is because insoluble fibre will speed up gut transit, leading to a worsening in symptoms.
Managing Bloating and Gas
If you struggle with bloating and gas, consider the following tips:
- Gradual Introduction: Increase fibre intake slowly to allow your digestive system to adjust.
- Drink Plenty of Water: Fiber absorbs water, so it’s important to stay hydrated, especially when increasing your fibre intake.
- Choose the Right Fibre: If gas and bloating are a concern, opt for soluble fibre sources like oats, apples, and psyllium, which are less likely to cause these issues than other more fermentable foods like wheat, onion or garlic.
Ensuring the right balance of fibre intake can be a minefield. If you are needing some adjustment to your fibre intake, to help relieve gastrointestinal symptoms or to improve your gut health, consider working with a dietitian such as myself to do so easily and with the peace of mind that your symptoms will not worsen.
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