In brief
Bacteria in the large bowel ferment the fibre and resistant starch your body cannot digest, turning them into short-chain fatty acids.
- Soluble fibre is found in fruit, vegetables, oat bran, barley, legumes and soy products.
- Some people with IBS find that certain foods trigger symptoms, including gas-producing foods, and a dietitian may help.
- Fibre is thought to lower the risk of bowel cancer by increasing stool bulk.
How it works
Fibre is made up of the parts of plants your body cannot digest. In the large bowel, bacteria ferment resistant starch and other fibre into short-chain fatty acids such as acetate, propionate and butyrate.
Butyrate can help protect against inflammatory disease, and a lack of it has been found in people with inflammatory bowel diseases such as Crohn's disease. Eating more foods containing resistant starch is one way to encourage a healthy microbiome. Add fibre to your diet slowly and drink enough water.
Connections
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Fibre fermentation and short-chain fatty acids needs
Gut microbes turn resistant starch and fibre into short-chain fatty acids such as acetate, propionate and butyrate.
Sources: Australian Academy of Science, Gut bacteria: the inside story; Better Health Channel (Victorian Government), Fibre in food
Bacteria in the large bowel ferment resistant starch into short-chain fatty acids.
Source: Better Health Channel (Victorian Government), Fibre in food
Fibre fermentation and short-chain fatty acids supports
- Gut barrier Emerging
Hungry gut microbes may feed on the gut's protective mucus lining, and the butyrate they make from fibre can help protect against inflammatory disease.
Source: Australian Academy of Science, Gut bacteria: the inside story
Sources
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Summarised from the Better Health Channel, the Australian Academy of Science and healthdirect. Sources read on 13 and 16 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.