What is fibre?
There has been a great deal of discussion about fibre recently, so this seems like a good opportunity to break it down and explore why it matters. Unlike some food trends that come and go – including expensive “superfoods” – the current attention being given to fibre is well deserved and, in many ways, much needed.
Dietary fibre occurs naturally in plant foods, including fruits, vegetables, nuts, seeds, wholegrains and legumes. It can broadly be classified into two categories: soluble and insoluble fibre.
| Soluble fibre | Insoluble fibre |
| Dissolves in water to form a gel-like substance during digestion. | Does not dissolve in water and moves through the digestive system relatively unchanged. |
| Can also be fermented by bacteria in the large intestine. | Adds bulk to stools and helps move digested food through the digestive tract. |
| Commonly found in oats, legumes, fruits and vegetables. | Commonly found in nuts, seeds, wholegrains and the skins of fruits and vegetables. |
They both work together to play an important role in supporting digestive health.
Why does fibre matter?
The following table outlines both the functions and the benefits of dietary fibre on our health:
| FUNCTIONS | BENEFITS |
| Adds bulk to diet which supports satiety | May reduce appetite |
| Slows the absorption of glucose | Works to lower blood sugar levels |
| Lowers total and LDL cholesterol | Reduction in the risk of cardiovascular disease |
| Helps to regulate blood pressure | Reduction in risk factors for diabetes and metabolic syndrome |
| Encourages the passage of foods through the digestive system | Improves bowel movement regularity |
| Adds bulk to stool | Alleviates constipation |
| Balances digestive pH and encourages intestinal fermentation | May reduce the risk of developing colorectal cancers |
(Dhingra et al, 2011)
Fibre and the gut microbiome
The gut microbiome is the community of bacteria and other microorganisms that naturally live, in varying numbers, within the digestive tract. Fibre plays an important role in supporting this community, as some fibres travel to the large intestine, where they are fermented by gut bacteria.
This fermentation produces compounds known as short-chain fatty acids, which help nourish the cells lining the bowel and contribute to a healthy gut environment.
Variety matters just as much as quantity.
A fibre-rich diet may also encourage a more diverse and resilient microbiome. Different plant foods contain different forms of fibre, which will support different groups of gut bacteria. Including a broad range of fibre-rich foods will support microbial diversity and overall gut health.
How much fibre do we need?
| WOMEN | MEN |
| 25g per day | 30g per day |
Despite this, many Australians are not consuming enough fibre. CSIRO research has previously reported that 83% of Australians did not meet suggested dietary levels.
Why it matters
Diets consistently lacking in fibre have been linked with a range of health concerns including:
· Constipation · Hemorrhoids · Diverticulitis · Irritable bowel disease · Obesity · Cardiovascular disease · Metabolic syndrome/diabetes · Some cancers, including bowel cancer
Together, this highlights the important role fibre plays in supporting digestive health and overall wellbeing.
When increasing fibre intake, it is best to do so gradually and ensure adequate fluid intake. Increasing fibre too quickly, or without drinking enough water, can contribute to abdominal discomfort, bloating or constipation.
What does 25–30g of fibre actually look like?
Fruit & vegetables
| FOOD | SERVING SIZE | FIBRE CONTENT |
| Raw carrot | 100g | 3.2g |
| Sweet potato (baked) | 100g | 3.2g |
| Broccoli (raw) | 100g | 3.5g |
| Kiwi fruit (without skin) | 100g | 1.8g |
| Apple (pink lady) | 100g | 3g |
| Banana | 100g | 2.2g |
Wholegrains
| FOOD | SERVING SIZE | FIBRE CONTENT |
| Rolled oats (uncooked) | 100g | 9.5g |
| Brown rice (boiled) | 100g | 1.7g |
| Whole meal bread | 100g | 6.9g |
| Pasta (boiled) | 100g | 2.7g |
Legumes, nuts & seeds
| FOOD | SERVING SIZE | FIBRE CONTENT |
| Tinned chickpeas (drained) | 100g | 5.7G |
| Lentils (cooked) | 100g | 4.1g |
| Chia seeds (dry) | 100g | 33.2g |
| Raw almonds (unsalted) | 100g | 11g |
(Food Standards Australia and New Zealand FSANZ)
Putting it into practice: Breakfast Bircher
| Ingredients ½ cup oats 1 tablespoon chia seeds, soaked in water ½ cup Greek yoghurt ½ cup kefir 1 medium grated apple Method Mix all ingredients and store overnight in the fridge. To serve: medium kiwi, 1 scoop of almond butter and a drizzle of honey. |
Approximately 15g of fibre per serve
This is around half of the recommended daily intake for men and more than half for women.
Small changes add up
The good news is increasing fibre doesn’t require expensive ingredients or a complete overhaul of the way we eat. Simple additions throughout the day can make a meaningful difference: fruit at breakfast, lentils in salad at lunch, nuts and veg sticks in the afternoon and wholemeal pasta for dinner.
Aim for variety rather than relying on one particular source. As we know, different plant foods provide different types of fibre, so including a broad selection throughout the week can offer greater benefits for digestive health and support the gut microbiome.
Perhaps fibre isn’t the newest superfood after all, but a timely reminder of just how valuable our everyday foods – and a little knowledge about them – can be.
This article provides general information only and is not intended as medical advice. Anyone with an existing digestive condition, or who has been advised to limit particular foods, should speak with an appropriate health professional before making dietary changes.