Dietary fibre is enjoying a resurgence as we learn to appreciate the role that it plays in gut health. We are also learning more about how important the gut is for our overall health and wellbeing. If you have ever suffered from constipation, diarrhoea, cramps, stitch, vomiting or bloating, you know better than anyone the effect this has on your physical and mental wellbeing, as well as your ability to exercise and not to mention enjoy it.

The food we eat has a huge effect on our gut and fibre has a big part to play in feeding all the beneficial bacteria that improve our health and immunity. Lots of people forget about fibre in their food. However, it’s time to start giving some thought to this mystery carbohydrate and all the wonderful things it does for us.

What is dietary fibre?

Dietary fibre is a type of carbohydrate derived from plants. Similar to the framing of a house, dietary fibre is responsible for the plant’s structure and shape. There are different types of dietary fibre, in the same way there are different materials available to build a house wall. All types of fibre have one thing in common; they can’t be broken down by our digestive enzymes and absorbed into our bloodstream. Instead, they travel fairly intact down through our gut to the large bowel.

Plant foods are generally high in dietary fibre. In fact, grains, legumes, fruits and vegetables are some of the most common sources of dietary fibre. The rising popularity of including more plant foods in our diet may mean we consume more fibre. However, as fibre is often located on the outside of a plant it can be removed during milling and food processing. Paying careful attention to how highly processed the plant foods are that you add to your diet will help you improve your gut health more effectively.

Consider the difference between wholewheat and white flour. Wholewheat flour contains all the parts of the wheat grain, while white flour has had the higher-fibre bran on the outside of the grain removed during milling and therefore it has much less fibre.

Types of dietary fibre

From a physiology perspective, there are two broad types of dietary fibre: soluble and insoluble. Each has its own unique health benefits.

Soluble fibre works like a sponge in our gut, soaking up water to form a soft gel. Good food sources include legumes (dried peas, lentils, chickpeas and beans), oats, barley, psyllium, and fruits (kiwfruit, apples, pears, citrus, stone and berry fruit). Soluble fibre helps soften stools so they can travel through the gut unrestricted. It also binds up cholesterol and sugar, as well as some carcinogens (cancer-causing substances), which then slows or even prevents their absorption into the bloodstream.

Insoluble fibre on the other hand does not dissolve in or take up water. Commonly known as “roughage” it is the tough material found in whole grains, nuts, seeds, fruit and vegetables (specifically the stalks, skins and seeds). These fibres make some foods look the same when they come out, as when they went in. Insoluble fibre adds bulk to stools, which, along with soluble fibre, helps keep us regular and prevents constipation.

Fibre can be added as an ingredient to foods during manufacturing to improve health benefits. This often occurs in cereals and bakery products. However, choosing bread and baked products with whole grains retained is preferable, as the fibre is still intact alongside the vitamins and minerals stored with it, rather than having been separated out, isolated as an ingredient and added back in. Whole-grain products are often less processed and contain less added sugar and additives.

Why is dietary fibre important?

Fibre gives your gut its own great exercise. While fibre might not be absorbed into our bloodstream, it has significant value in supporting a healthy gut microbiome (all those helpful gut bacteria that help us maintain great health).

Just as exercising keeps your body strong, fit and healthy, fibre keeps your gut strong, fit and healthy. Your gut is really important for many aspects of your health, particularly your immune system. It’s like the silent sentry, or soldier, for your immune system. Our first line of defense for our body is our skin and our gut. It’s time to let fibre stand to attention.

Fibre adds bulk to stools and helps stools pass through the gut more quickly. This faster travel time not only helps prevent constipation, but also minimises the opportunity that any bugs or carcinogens present in our food have to try and enter our body. At the same time, soluble fibre’s sponge-like properties help prevent diarrhoea by absorbing water into the stools and helping them pass through our gut better. Fibre also helps keep blood sugars constant by slowing the release of sugar from food.

Fibre and gut issues

On the flip side, because intense exercise can impact the blood supply to the gut, sometimes a high fibre food can be harder to digest if we launch straight into high-intensity exercise afterward. This can sometimes contribute to gut discomfort during exercise, so you may want to consider allowing more time for that food to digest before heading into a hard training session. We’ll elaborate more on this later.

A sudden jump in fibre intake in your diet can also lead to some gut symptoms. However, you can train your gut by adding extra high-fibre foods in gradually. You can test a new high-fibre food one at a time and observe how you feel. Everyone is different with what they notice and what they don’t, depending on their usual fibre intake and how hard that particular training session is. It’s a good idea to experiment to figure out what works best for you.

As a result of fibre’s sponge-like properties, it’s important to drink plenty of fluid to help your dietary fibre work its magic. Fibre needs liquid to soak up with it to keep your stools soft. Increasing your fibre in the absence of water can cause tummy upset and make constipation worse. Fluid keeps the flow.

Tips to boost the dietary fibre in your diet

• Try adding lentils, chickpeas, beans or barley to soups and salads
• Choose whole grain versions of breads, crackers, pasta and cereals
• Replace white flour with wholewheat flour in baking
• Snack on nuts, seeds, and fruit or add them to salads 
• Add hummus into your diet by pairing with carrot sticks or having it in sandwiches
• Add ground flaxseeds to your breakfast cereal or smoothies
• Choose popcorn over potato chips
• Keep the skin on your fruit and vegetables, even when making a homemade smoothie or juice – the skin packs the most fibre
• Thinly slice and stir fry the stalks of vegetables like broccoli, pak choy, celery, cauliflower and choy sum