Fibre is the indigestible parts of plant foods. It plays a very important role in keeping our digestive system healthy and has a range of other functions including lowering cholesterol, reducing constipation, lowering blood glucose levels and promoting healthy gut bacteria. In the long-term, eating enough fibre can help prevent bowel cancer, haemorrhoids and diverticular disease, and can assist in preventing and managing diabetes and heart disease.
Soluble fibre attracts water and turns gel-like during digestion. It helps slow the emptying process in our stomachs and keeps us feeling fuller and more satiated after eating. It also helps to lower cholesterol (dietary cholesterol binds with fibre and isn’t absorbed) and blood glucose levels (our bodies take longer to digest a fibre-containing meal, thereby slowing the release of glucose). Soluble fibre can also help with constipation.
Good sources include most fruits, vegetables, oats, barley, legumes (including soy products), and seeds.
Insoluble fibre moves down to the colon where it absorbs water, softening and adding bulk to the contents of our bowels, helping with regular bowel movements. It also helps to keep us full and keeps our bowels healthy (it’s like a toothbrush for the gut).
Insoluble fibre is made up of the structural parts of plant cell walls. The best dietary sources are wholegrain breads and cereals, nuts, seeds, and the skin of fruit and vegetables.
We don’t technically digest resistant starch- our gut bacteria do that job for us. Resistant starch is a ‘prebiotic’ which means it’s a food source for our gut bacteria. It moves undigested through the small intestine and ends up at the large intestine. This is where our gut bacteria ferments the resistant starch and change them into short-chain fatty acids. Short-chain fatty acids are important to bowel health, may protect against cancer, also may play a role in lowering blood glucose levels.
Resistant starch is found in unprocessed cereals and grains, unripe bananas, potatoes and lentils.
How much should we aim for each day?
Eating 25-30g each day will help us receive all the wonderful benefits that fibre has to offer. This isn’t very much if we’re consuming a mix of fruits, veggies, nuts, seeds and grains every day. To give you an idea, here are the fibre contents of different types of food:
- 1 cup carrots, skin on: 7g
- 1 medium cob of corn: 6
- 100g kidney beans: 7g
- 1/2 cup rolled oats: 4.5g (vs. Nutri-grain: 1.5g, vs. Cocopops: 0.5g)
- 1 cup brown rice: 2.7g (vs white rice: 1.6g)
- Handful of almonds: 2.6g
- 2 slices wholegrain bread: 5g (vs. white bread: 2g)
It doesn’t take anything exotic or special to get enough fibre.
- A breakfast of rolled oats and a medium banana would contain about 8g fibre.
- A sandwich on wholegrain bread would have at least 5g fibre (and more if you fill it with veggies!).
- A snack of an apple and a handful of nuts would contain about 4g fibre.
- A dinner with a cup of brown rice and a cup of mixed veggies (skin on) would contain about 10g fibre.
That’s ~27g fibre in a day– a great amount!
Don’t forget water
Remember that fibre attracts water- you’ll need to ensure you’re consuming enough water to help the fibre move through your digestive system.
If you’re currently not eating a lot of fibre, slowly increase your intake to allow you body to get used to it, and drink water throughout the day.