While you might know that fibre improves bowel health and helps keep you fuller for longer, dietary fibre has several other health benefits.
Let’s take a look at what dietary fibre is, which foods are the best high-fibre foods and 3 surprising reasons why you need more fibre.
What is fibre?
It seems across history, empirical knowledge and modern research on dietary fibre is well substantiated. In 430 BC, Hippocrates was said to compare the laxative effects of coarse wheat and refined wheat, with many health benefits. Fast forward to the 1920’s where U.S. doctor John Kellogg brought cornflakes and the health benefits of bran to the Western world.
So what exactly is fibre?
Strictly speaking, fibre is the partly digestible and indigestible compounds of plants, which pass relatively unchanged through our stomach and intestines. Fibrous foods are digested slowly, which helps maintain the feeling of fullness.
Almost all fibre consumed by humans can be classified as a carbohydrate. The difference between fibre and traditional carbs is that fibre has chemical bonds between each sugar molecule, whereas carbohydrates are just single or multiple units of sugars.
Some of these bonds are complex and can’t be broken down by human enzymes in the digestive tract. Yet they provide an important food source for digestive bacteria. The fibre we consume in our diet, whether it’s for us or our gut bacteria is commonly termed dietary fibre.
There are two types of dietary fibre: Soluble Fibre & Insoluble Fibre.
These include pectins, gums, mucilage and are mainly found within the cells of plants and vegetables. Soluble fibre can be broken down in the digestive system by enzymes. It forms a gel that slows down gastric emptying and transit time (speed at which food moves through the digestive tract). One of the major roles of soluble fibre is to lower LDL cholesterol as well as regulating bowel health and promoting proper elimination.
Soluble Fibre Foods:
- fruits, vegetables, barley, chia, seed husks, flaxseeds, psyllium husk, dried beans, lentils and peas.
Examples of insoluble fibre include cellulose, hemicelluloses and lignins. These make up the structural parts of plant cell walls. A major benefit of consuming insoluble fibre is to add bulk to digested food, making it easier to pass through the digestive tract. Insoluble fibre is not digested by the body, however it provides a food source to intestinal microbes.
Insoluble Fibre Foods:
- skins of fruits and vegetables, nuts, seeds, dried beans and wholegrains.
Dietary Fibre Compounds
- β-Glucans (Beta-Glucans): β-Glucans are sugar polymers found in oats and barley.
- Gums: Gums are viscous polysaccharides often found in seeds. Guar gum extracted from guar beans contains mannose and galactose. It is used as a food thickening agent.
- Hemicelluloses: Hemicelluloses are a large group of polysaccharides (sugar polymers) that are broken down into various simpler sugars. These include glucose, xylose, arabinose, mannose, galactose, rhamnose, or pentose.
- Inulin: Inulin is a mixture of fructose chains that vary in length. Inulin occurs naturally in plants, such as onions and Jerusalem artichokes.
- Pectins: Pectins are another polysaccharide group made of 300 to 1,000 simple sugars. Pectins are soluble, viscous fibres that are abundant in berries and apples.
- Resistant starch: Naturally occurring resistant starch is an indigestible sugar found in plant cell walls. It is fermented and broken down by gut microbes. Bananas, legumes, cooked and cooled rice and potatoes and legumes are food sources of resistant starch.
What’s the recommended daily intake for fibre?
For adults, the Australian RDI is 30-35g of fibre per day. This equates to around ½ cup cooked legumes, cereal, vegetables or fruit per day.
Health Benefits of Fibre
- Lowers cholesterol
- Improves glycemic control
- Lowers blood pressure
- Improves bowel function
- Supports cardiovascular health
- Prevents metabolic syndrome & diabetes
- Helps prevent bowel cancers
- Maintains healthy weight
3 Surprising Reasons You Need Fibre
We know fibre is important for gastrointestinal health. Fibre helps regulate the bowels and reduces the risk of developing certain bowel diseases. In fact, a recent meta-analysis from 2020 shows that on average, consuming 30g of fibre (cereals, fruits, vegetables) per day reduces the risk of developing diverticular disease by 41%.
However, fibre has some other interesting therapeutic benefits, outside of the digestive system. Here’s 3 reasons (you didn’t know) why you should include more fibre in your diet.
Dietary Fibre helps with:
- Depression & Anxiety
- Bone Health
- Weight management
Depression & Anxiety
Research supports the addition of dietary fibre to support mental health, depression and anxiety. Fibrous compounds, known as fructo-oligosaccharides, improved anxiety and depression in participants, as noted in a recent scientific review paper. The article showed that a modest amount of 5g per day of fibrous fruits and vegetables boosted bifidobacteria species and enhanced the participants’ mood and depressive symptoms.
An interesting benefit of fibre is that it helps maintain skeletal health. Prebiotic fibres are beneficial for improving calcium absorption and increasing bone mineral density, especially in populations with inadequate calcium intake. Fibre also appears to reduce bone loss and reduce the risk of fractures, particularly in elderly individuals. Specifically, oligosaccharides, oligofructose and inulin show priming effects in bone health research.
Many health issues develop from the onset of obesity, including type 2 diabetes and heart disease. Excess fat deposition puts pressure on body structures, organs and the cardiovascular system. The risk of developing cardiovascular disease is much higher in an obese population compared to those within a healthy weight range. The inclusion of dietary fibre helps with weight management in several ways. Fibre helps with satiety, as discussed, which helps mitigate the risk of overeating or consuming nutrient-poor foods. The research shows that dietary fibre has protective qualities for each body system usually involved in obesity-related chronic diseases.
Best High-Fibre Foods
- Legumes (peas, lentils, kidney beans)
- Grains (bran cereal, oats, barley, quinoa, brown rice)
- Vegetables (butternut squash, artichoke, spinach, mushrooms, brassica vegetables)
- Fruit (prunes, pear, berries, fresh plums)
- Nuts (almonds, pistachios, pine nuts, hazelnuts, pecans, peanuts)
Drug & Nutrient interactions
β-glucan, psyllium, pectin and other slow-moving fibres have the potential to hinder the absorption of drugs and mineral supplements if taken concurrently. It’s always best to consult a trusted health provider if you want advice on when to include or avoid high-fibre foods or fibre supplements.
How To Increase Your Fibre Intake
Here’s some ways to increase your dietary fibre intake:
- Add 2 tablespoons of psyllium husk powder or chia seeds to smoothies
- ½ cup cooked chickpeas to a salad
- ½ cup green lentils to a classic bolognese sauce
- Enjoy plenty of fibrous vegetables like kale, cabbage, artichokes, broccoli and cauliflower
- Increase fruit such as berries, pears, dates, guava, prunes, apples (skin on) and oranges
Aleixandre, A., & Miguel, M. (2016). Dietary fiber and blood pressure control. Food & function, 7(4), 1864–1871. https://doi.org/10.1039/c5fo00950b
Aune, D., Sen, A., Norat, T., & Riboli, E. (2020). Dietary fibre intake and the risk of diverticular disease: a systematic review and meta-analysis of prospective studies. European journal of nutrition, 59(2), 421–432. https://doi.org/10.1007/s00394-019-01967-w
Bozzetto, L., Costabile, G., Della Pepa, G., Ciciola, P., Vetrani, C., Vitale, M., Rivellese, A. A., & Annuzzi, G. (2018). Dietary Fibre as a Unifying Remedy for the Whole Spectrum of Obesity-Associated Cardiovascular Risk. Nutrients, 10(7), 943. https://doi.org/10.3390/nu10070943
Hijová, E., Bertková, I., & Štofilová, J. (2019). Dietary fibre as prebiotics in nutrition. Central European journal of public health, 27(3), 251–255. https://doi.org/10.21101/cejph.a5313
Gill, S. K., Rossi, M., Bajka, B., & Whelan, K. (2021). Dietary fibre in gastrointestinal health and disease. Nature reviews. Gastroenterology & hepatology, 18(2), 101–116. https://doi.org/10.1038/s41575-020-00375-4
Simpson, H. L., & Campbell, B. J. (2015). Review article: dietary fibre-microbiota interactions. Alimentary pharmacology & therapeutics, 42(2), 158–179. https://doi.org/10.1111/apt.13248
Swann, O. G., Breslin, M., Kilpatrick, M., O'Sullivan, T. A., Mori, T. A., Beilin, L. J., Lin, A., & Oddy, W. H. (2021). Dietary fibre intake and its associations with depressive symptoms in a prospective adolescent cohort. The British journal of nutrition, 125(10), 1166–1176. https://doi.org/10.1017/S0007114520003426
Taylor AM, Holscher HD. A review of dietary and microbial connections to depression, anxiety, and stress. Nutr Neurosci. 2020 Mar;23(3):237-250. doi: 10.1080/1028415X.2018.1493808. Epub 2018 Jul 9. PMID: 29985786.
Whisner, C. M., & Castillo, L. F. (2018). Prebiotics, Bone and Mineral Metabolism. Calcified tissue international, 102(4), 443–479. https://doi.org/10.1007/s00223-017-0339-3
Wong, C., Harris, P. J., & Ferguson, L. R. (2016). Potential Benefits of Dietary Fibre Intervention in Inflammatory Bowel Disease. International journal of molecular sciences, 17(6), 919. https://doi.org/10.3390/ijms17060919