The importance of dietary fibre for your gut

Dr Michael Conlon
Written by
Dr Michael Conlon
Principal Research Scientist at the CSIRO
Is it really a diet if it tastes so good?

Eating a diet rich in dietary fibre is a great way to improve the health of your digestive system. Dietary fibres are commonly referred to as complex carbohydrates as they’re not completely broken down in the digestive system and are found in plant-based foods, such as grains, fruits, vegetables, legumes and nuts. To achieve a high fibre intake and good gut health, we need to eat at least 25-30g of fibre each day.  

What 31g of fibre looks like each day:

Breakfast:

30g whole wheat breakfast cereal flakes (6.5g fibre) with 100g thick yoghurt or 100ml milk + 1 medium, just-ripe banana (3g) (total= 9.5g fibre)

Morning tea:

100g vegetable sticks (1 carrot + 2 Lebanese cucumbers with skins on for 2.5g fibre) + 20g (1tbs) hummus (1g fibre) (total= 3.5g fibre)

Lunch:

2 slices of Helga’s Digestive Wellbeing Barley, Seeds & Grain bread (5.5g fibre) + 2 cups of salad (tomato, cucumber and lettuce for 2g fibre) + 50g smashed avocado (2.5g fibre) + 50g of pulled chicken (total= 10g fibre)

Dinner:

Chilli Con Carne: 100g beef strips + ½ cup cooked red kidney beans (5g fibre) + 2 cups of cooked cauliflower rice (3g fibre) + Mexican spice (total = fibre 8g)

To reduce the risk of chronic disease, such as diabetes and heart disease, a higher daily intake of at least 28-38g is recommended, which is as simple as having two medium, unpeeled carrots extra in a day (8g fibre) or 125g of fresh berries (7g).

Want to compare a high-fibre versus low-fibre diet plan? Join the challenge to access our sample high-fibre and low-fibre diet plans.

A diet that has a range of fibre-rich foods will feed many hundreds of different gut microbes present in each of us. Since different types of fibre vary in their ability to promote good gut health, the best option is to eat a wide range of fibre-containing foods that are as close to their natural states as possible. This way, you’ll enjoy the range of health benefits they provide.

Types of fibre in foods


Fibres are classified as soluble and insoluble (including resistant starch).

Soluble fibres dissolve in water, forming thick gels in the upper gut that slow the passage of food and influence the rate of nutrient uptake, including glucose. Soluble fibre is known to help you feel fuller for longer and is also beneficial in helping lower cholesterol. Good sources of soluble fibre include fruits, vegetables, oat bran, barley, seed husks, flaxseed, psyllium, dried beans, lentils and peas.

Insoluble fibres absorb water and provide bulk to digested food. This action promotes smooth passage of food through the gut, keeping your bowel motions regular. Good sources of insoluble fibre include wheat bran, corn, rice bran, the skins of fruits and vegetables, whole grains, nuts and seeds, lentils, kidney beans and chickpeas.

Resistant starch is a type of insoluble fibre that is highly effective in stimulating gut fermentation in a manner similar to soluble fibres. Unlike other fibre, resistant starch is preferentially fermented by our gut bacteria and its fermentation produces butyrate – a substance which has an important effect on maintaining the integrity of our gut wall, our immune system and aids in healthy digestion. Good sources of resistant starch are chickpeas, firm bananas, BarleyMax™ grains, artichokes, rye and millet.

The different types of fibre present in these foods will also fuel the growth and activity of the diverse ‘army’ of microbes in the large intestine. Feeding the gut microbes a range of dietary fibre will maximise the range of beneficial substances being produced in the gut (such as butyrate and acetate). These substances reduce the risk of nasty microbes growing in this environment, allowing an increase in good gut microbiota.

What is BarleyMax™?
BarleyMax™ is a specialised grain that contains a mix of dietary fibres which can assist you in achieving good gut health.

Over the next few days, review your pantry. Do you already have some of the pantry stables we’ve listed? You may find you already have many of the fibre rich foods in your pantry or fridge. If so, add a few more sources of fibre to you shopping list. However, if you’re seeing a fibre shortage, go through the list and start swapping your foods around. Do you use white bread? If so, swap this for a wholegrain or fibre-enriched product. What about your snacks? Having nuts as a snack is a good way to increase your fibre. It’s good to keep in mind that small changes can make a big difference.

This article was written by
Dr Michael Conlon
Dr Michael Conlon
Dr Michal Conlon is a principal research scientist at CSIRO Health and Biosecurity Business Unit in the Food and Nutrition Program. He holds a PhD in biochemistry from the University of Adelaide and has more than 30 years’ experience in investigating the impact of foods and diets on physiological processes and health outcomes by conducting pre-clinical and clinical research trials. A focus of Dr Conlon’s work has been on understanding the effects of dietary components such as fibre, resistant starch, proteins and oils on gut physiology, as well as other tissues and systems of the body. The work has also involved investigating the roles of microbes such as bacteria in mediating the effects of diet on the large bowel, including studies to investigate or develop prebiotic fibres and probiotics. Dr Conlon has been instrumental in conducting a series of research activities which have shown that the inclusion of resistant starch and fibres in the diet can help protect against the toxic effects of poor ‘western’ diets on the large bowel. This included demonstrating that resistant starch can reduce the risk of tissue damage which may contribute to serious diseases of the colorectal region. This vast body of research has also demonstrated the important role of fermentation by gut microbes in producing short chain fatty acids (SCFA) which help to maintain a healthy environment within the large bowel. Dr Conlon has continued to apply his research to understanding and helping prevent adverse health conditions such as inflammatory bowel disease and colorectal cancer. He also has a keen interest in developing new foods and nutraceuticals with gut health applications from under-utilised resources.

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