Discover How Fibre Can Improve Your Health
Dietary fibre is essential for maintaining metabolic and gut health, yet most people in Ireland and the UK consume far less than the recommended daily amount. (1) This post explores the critical importance of fibre and how increasing your intake can dramatically improve your health.
What is Fibre?
Fibre refers to carbohydrate polymers that are resistant to digestion by human enzymes. It includes fermentable fibre, which supports gut microbiota, and non-fermentable fibre, which aids in intestinal motility. As it is not broken down or absorbed in the small intestine, fibre passes into the large intestine largely unaltered.
Different Types of Fibre
It is classified into two main sub-types: fibre that can dissolve in water (soluble dietary fibre) and fibre that cannot (insoluble dietary fibre). Soluble fibre is found in high quantities in pulses such as beans, chickpeas, lentils, and in oats, barley, fruits, and nuts. Insoluble fibre is found in leafy green vegetables such as kale and cabbage, cruciferous green vegetables such as broccoli, as well as in whole grains, nuts, seeds, and vegetables.
Why is Fibre Important?
Fibre has multiple functions in both the small and large intestines, and eating sufficient quantities of fibre is vital for the maintenance of metabolic health.
Both soluble and insoluble fibre tend to slow the absorption of nutrients, including carbohydrates, in the small intestine. This lowers the glycaemic index of meals and reduces spikes in blood glucose levels, which in turn prevents high levels of blood insulin. Keeping blood insulin low and avoiding repeated or persistent high levels helps maintain the sensitivity of the insulin receptors on muscle, fat, and liver cells. Maintaining insulin sensitivity combats the development of metabolic syndrome and reduces the risks of non-communicable chronic diseases such as cardiovascular disease, diabetes, and multiple cancers.
Fibre is Good for Your Gut
In the large intestine, fibre nourishes the gut microbiota, which feed on soluble fibre, breaking it down into short-chain fatty acids (SCFAs). Short-chain fatty acids, such as butyrate, propionate, and acetate, nourish colon cells, regulate immune responses, and help maintain a healthy gut lining. These are incredibly beneficial compounds with multiple health benefits that warrant a separate article.
In the context of blood glucose control, one of the most important of these benefits is that they stimulate the release of gut hormones (also called incretins) such as GLP-1. These hormones improve blood glucose control and insulin sensitivity, increase satiety, reduce cravings, and help prevent overeating. This is all extremely helpful in the management of body weight. In addition to SCFAs, the metabolism of fibre by the microbiome generates numerous other signalling molecules that have beneficial effects throughout the body.
Soluble dietary fibre, such as pectin and beta-glucan, also forms gel-like substances that can trap nutrients, keeping them inside the small intestine lumen for longer and helping prevent the contents of the gut from becoming too solid. This adds bulk to the intestinal contents, allowing the regular contractions of the muscular wall to more easily squeeze the contents through the gut. The combination of bulkier and softer intestinal contents speeds up transit through the large intestine, preventing constipation. This reduces the time that harmful compounds, such as secondary bile acids and food-derived carcinogens, can interact with intestinal cells and is of major benefit in preventing cancers of the colon, one of the most common forms of cancer in Ireland and the UK. By avoiding constipation, fibre helps prevent diseases such as diverticulosis and diverticulitis.
Fibre Reduces Cholestrol
Another important direct action of fibre is to reduce levels of low-density lipoproteins (LDL) and triglycerides (a core component of dietary fats) in the blood. It does this directly by binding bile acids (containing cholesterol) and fats in the intestines, preventing their absorption into the blood and increasing their excretion. Fibre also indirectly, through the actions of SCFAs, reduces the synthesis of cholesterol in the liver and increases the clearance of LDL particles by the liver.
Recommended Dietary Intakes of Fibre
An adequate fibre intake is a critical element of a healthy diet. Current recommended daily intake in Europe is 25g per day for an adult(2) whereas in the USA the Adequate Intake is set at 25g for adult women and 38g per day for adult men.(3) The differences are somewhat irrelevant at the moment as, and most people eat nowhere near enough fibre, and average intakes in Europe and the USA are well below 20g per day.
How to Increase Your Fibre Intake?
Incorporating fibre-rich foods like whole grains, legumes, nuts, fruits, and leafy green vegetables into every meal is a simple way to boost your fibre intake and protect your health.
Start slowly with smaller amounts to get used to an increased intake and then aim to slowly build your consumption to at least 30 grams of fibre daily and you will benefit maximally from the profound boost to your health that fibre has to offer.
31 Jan. 2025 - Dr. Steve Collins
1. Irish Heart Heart of the matter-Facts on Fibre - Irish Heart [Internet]. [cited 2023 Apr 19]. Available from: https://irishheart.ie/news/heart-of-the-matter-facts-on-fibre/
2. Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal. 2016 May 23;8(3).
3. Institute Of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). National Academies Press; 2005. 1–1331 p.