Dietary fibres are plant-based carbohydrates that are not absorbed in our digestion. Even though our digestive system is not able to digest dietary fibre, eating enough fibre is crucially important to our health.
Food products contain a mixture of different fibres. Most of the fibres our diet contain are insoluble, while the rest - about one fifth - are soluble. Soluble and insoluble fibres affect our health in different ways, but both are needed to keep the gut healthy.
Soluble fibre from legumes, berries and fruits
Berries, fruits and legumes are good sources of soluble dietary fibre, and oat and barley also contain plenty of it. During digestion, soluble fibre absorms a lot of water and gels. It helps control sugar metabolism by making the food mass thicker, which slows down the emptying of the stomach and helps reduce sharp increases in blood sugar after eating.
Soluble fibres are more gentle to the gut and that's why they are recommended for those suffering of IBS (Irritable Bowel Syndrome).
Insoluble fibre from whole grain products
Whole grain products like porridges and whole grain bread contain insoluble fibre, which promotes gut well-being by, for example, building up the content of the gut and thereby improving bowel function. While the content of the gut increases, the impact of harmful dietary substances in the gut is also diluted.
The bacteria in the large intestine is fed with dietary fibre during fermentation, which produces short-chain fatty acids and hence lowers the pH in the gut. Lower pH in the gut increases the amount of favourable bacteria in the large intestine, and short-chain fatty acids are an important source of energy for the cells in the gut mucous membrane, for example.
What about FODMAPs?
FODMAPs are carbohydrates that are not absorbed in the small intestine. When they enter the large intestine they are quickly fermented, which increases gas production in the gut and can cause unpleasant symptoms - bloating, stomach ache and flatulence. Because of their rapid fermentation, FODMAPs cause painful stomach symptoms for those who suffer of IBS. Fibre is fermented in the large intestine much slower than FODMAP carbohydrates, which results in more even gas production.
Eating less FODMAP carbohydrates reliefs the gut symptoms of many IBS patients. However, the low-FODMAP diet also includes less of many common fibre sources, such as rye products. It is therefore important that those with gut problems pay enough attention on getting a sufficient amount of necessary fibres from other sources. Oat, psyllium, quinoa and flaxseeds, for example, are good sources of fibres that may be more suitable for those with a sensitive gut, but the way we tolerate FODMAP carbohydrates or fibres varies from person to person.
FODMAP is short for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.