Dietary Fibre & Health
What is Dietary Fibre?
Fibre is a type of carbohydrate that cannot be digested or absorbed in the small intestine. Unlike other carbohydrates, which are broken down into glucose and absorbed, dietary fibre remains largely intact as it moves through the digestive system. This changes once it reaches the large intestine, where it undergoes partial or complete fermentation.
Which Foods Contain Dietary Fibre?
Dietary fibre is found in plant foods:
Fruits
Vegetables
Whole grain breads and cereals
Legumes and pulses
Seeds & nuts
What are the Different Types of Dietary Fibre?
There are various dietary fibres, each with distinct physicochemical properties such as solubility, viscosity, and fermentability, that determine their functionality in the gastrointestinal tract.
Soluble Fibre
Soluble fibre is a dietary fibre that dissolves in water to form a thick gummy gel-like substance in the digestive system.
This type of fibre helps to keep you feeling fuller for longer, regulates blood sugar levels and lowers cholesterol by slowing the absorption of fat and glucose into the bloodstream.
Insoluble Fibre
Insoluble fibre is a dietary fibre that does not dissolve, instead, it absorbs water adding bulk to the stool, speeding up its passage through the digestive tract.
This type of fibre helps to keep things moving through your digestive system supporting regular bowel movements, preventing constipation and reducing the risk of haemorrhoids and diverticular disease.
Prebiotic Fibre
Prebiotic fibre is a dietary fibre fermented by beneficial gut microbes to stimulate the growth of beneficial bacteria and/or metabolites conferring a health benefit to you ‘the host’.
This type of dietary fibre is associated with a plethora of health benefits including improved immune system defence, gut barrier permeability, reduced inflammation, increased mineral absorption, and protection against colon cancer.
How Important is Dietary Fibre for Health?
Dietary fibre is essential for human health, not only due to its physical properties but also because of its impact on the gut microbiota. It’s so important that it is considered one of the five macronutrients—nutrients required in large amounts for health—including carbohydrates, protein, fat, fibre, and water.
A low intake of dietary fibre has been linked to the development of metabolic disorders, inflammatory diseases, and certain cancers, while a high intake of dietary fibre is associated with positive health benefits.
Gastrointestinal Health
Regular bowel movements
Irritable Bowel Syndrome
Constipation
Diarrhoea
Diverticular disease
Inflammatory bowel disease
Colorectal cancer
Gut Microbiota
Decrease in pathogenic ‘bad’ bacteria populations
Increased beneficial ‘good’ bacteria such as Lactobacilli and Bifidobacteria
Immune function
Digestion
Inflammation
Nutrient uptake
Cardiovascular Disease
Cholesterol levels
Blood pressure
Type 2 Diabetes and Gestational Diabetes
Blood glucose levels
Insulin sensitivity
Bone Health
Calcium absorption
Mental Health
Gut-brain-axis
Brain function and cognition
Inflammation
Influence on neurotransmitters serotonin, dopamine, GABA, and glutamate.
How Much Fibre is Recommended?
The Australian Dietary Guidelines provide the following recommendations for dietary fibre intake.
Adequate Intake (AI):
Males: 30g
Females: 25g
Adequate Intake refers to the average daily nutrient level that is assumed to be sufficient to meet the nutritional needs of most healthy people. AI is used when there isn’t enough scientific evidence to establish a more precise Recommended Dietary Intake (RDI).
Suggested Dietary Target (SDT)
Males: 38g
Females: 28g
The suggested dietary target is the amount recommended to reduce chronic disease risk.
How Much Fibre are Australians Consuming?
A 2018 study found that the median dietary fibre intake among Australian adults was 20.7 g per day, with individual intakes ranging from 14.3 g to 28.7 g daily. Fewer than one-third (28.5%) met the Adequate Intake (AI) for fibre, and only 14% achieved the Suggested Dietary Target (SDT).
More females met the SDT, compared to males, although neither group consistently reached the AI.
Young adults aged 19–30 years were the least likely to meet the SDT, while adults aged 51–70 years were the most likely to.
Fibre intake was higher among adults in the highest socioeconomic status (SES) bracket compared to those in the lowest SES bracket.
Top Soluble Fibre Foods
Oats and barley
Peeled fruits and berries
Most vegetables
Legumes (beans) and pulses (lentils)
Smooth nut butters
Top Insoluble Fibre Foods
Wholemeal and whole grain breads and cereals
Unpeeled fruits and vegetables
Nuts and seeds
Top Prebiotic Fibre Foods
Onions, leeks, celery, asparagus, garlic, and artichokes
Legumes (beans) and pulses (lentils)
Cooked and cooled potatoes
Green bananas, apples, blueberries
Whole grains
References
Cronin, P., Joyce, S. A., O'Toole, P. W., & O'Connor, E. M. (2021). Dietary Fibre Modulates the Gut Microbiota. Nutrients, 13(5), 1655. https://doi.org/10.3390/nu13051655
Fayet-Moore, F., Cassettari, T., Tuck, K., McConnell, A., & Petocz, P. (2018). Dietary Fibre Intake in Australia. Paper I: Associations with Demographic, Socio-Economic, and Anthropometric Factors. Nutrients, 10(5), 599. https://doi.org/10.3390/nu10050599
National Health and Medical Research Council. (n.d.). Dietary fibre. Nutrient reference values for Australia and New Zealand. Retrieved January 19, 2025, from https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/dietary-fibre
Ramsteijn, A. S., & Louis, P. (2024). Dietary fibre optimisation in support of global health. Microbial biotechnology, 17(8), e14542. https://doi.org/10.1111/1751-7915.14542
