The fermentation of dietary fibre in the large bowel regulates microbial activity and the production of good gut bacteria in our gut. This leads to the production of short chain fatty acids such as butyrate which play a vital role in gut barrier function; regulation of blood glucose levels; immune function; appetite regulation; obesity and may be effective in protection against bowel diseases such as colorectal cancer and inflammatory bowel diseases.
There a 3 kinds of dietary fibre: soluble, insoluble and resistant starch each playing a different role. We know that inadequate intake of dietary fibre can lead to adverse health effects and an increase risk of gut conditions such as diverticular disease as well as cholesterol lowering properties.
Soluble fibre dissolves in water to form a thick gel in your intestines, slowing down digestion. Foods containing this type of fibre can help stabilise blood glucose levels in people with diabetes and may help to lower LDL (unhealthy) cholesterol levels by collecting fatty deposits as it moves through the intestine. By slowing down digestion, foods that are high in soluble fibre can help people feel fuller for longer after eating. Foods higher in soluble fibre include: Fruits and vegetables; Beans and lentils; Oats.
Insoluble fibre does not dissolve in water and is found in foods like wholemeal bread, wheat bran, vegetables and nuts. Insoluble fibre adds bulk to stools by absorbing water, and helps to keep bowels regular. It is important to increase your fluid intake as you increase fibre. Without fluid, the fibre stays hard, making it difficult to pass and causing constipation.
Resistant starch is a form of starch that cannot be digested in the small bowel. As a result it is a type of fibre. It is found naturally in some foods such as bananas, potatoes, grains, and legumes and is also produced or modified commercially and incorporated into some food products.
Human studies have demonstrated that including foods rich in resistant starch within a meal is useful for controlling blood glucose and there is some evidence that it might help us to feel more full after meals, which could mean we snack less. There is also a lot of interest in potential benefits for gut health.
When reading nutrition labels look for more than 7g dietary fibre per 100g, remembering that dairy products do not contain fibre. Eating a wide variety of plant based foods can help to ensure you meet your daily fibre requirements.
- Role of Gut Microbiota-Generated Short-Chain Fatty Acids in Metabolic and Cardiovascular Health Curr Nutr Rep. 2018; 7(4): 198–206. doi: 10.1007/s13668-018-0248-8
- Baxter NT, Schmidt AW, Venkataraman A, Kim KS, Waldron C, Schmidt TM. 2019. Dynamics of human gut microbiota and short-chain fatty acids in response to dietary interventions with three fermentable fibers. mBio 10:e02566-18. https://doi.org/10 .1128/mBio.02566-18