Updated: Dec 7, 2020
Estimated reading time:4 minutes
Fibre is incredibly important. The intake of fibre through various foods plays a vital role in reducing the risk and lowering the incidence of numerous diseases.
On average, the UK population only eats about 18g of fibre a day (1), well below the recommended 30g per day. Children need proportionally less (see table below). However, on average, children and teenagers are only getting around 15g or less of fibre a day (2).
WHAT IS DIETARY FIBRE?
Dietary fibre, commonly known as ‘roughage’, is that part of plant material in the diet which is resistant to (cannot be completely broken down by) digestive enzymes. This includes cellulose, hemicelluloses, pectins, lignin, inulin, gums, mucilages, beta-glucans, resistant starch and oligosaccharides. Micro components such as waxes, cutin and suberin are also included (1). Fibre rich foods include vegetables, fruits, legumes, whole grains, nuts and seeds.
CLASSIFICATIONS OF FIBRE
Traditionally, dietary fibre was classified according to its solubility. Soluble fibres were considered to have benefits on cholesterol, while insoluble fibres were linked with laxation benefits. This division is still used in nutrition labelling, however, scientific evidence supporting that soluble fibres lower cholesterol and insoluble fibres increase stool weight is inconsistent (3). Both are equally important and most fibre rich foods will typically contain both, so you don’t need to worry too much about which one you are consuming. You can read more about the health benefits of fibre in my next blog post.
There are various types of fibre, some of which are almost completely fermented by gut bacteria, while others are less fermentable. Fermentable fibres are present in virtually all fruits, vegetables and legumes. They are also in nuts, seeds and grains and provide fuel for bacteria, which may encourage a healthy microflora in the gut (1). Healthy bacteria in the gut feed on fermentable fibre and turn it into short chain fatty acids. In turn, those fatty acids control appetite and blood sugar (4), tamp down inflammation and improve immune function (3)(5). Specific short chain fatty acids may reduce the risk of developing gastrointestinal disorders, cancer and cardiovascular disease (6). Some fermentable fibres, for example beta glucan in oats, have other health benefits too, including moderating blood glucose levels and helping to maintain healthy cholesterol levels (2)(7). Less fermentable fibres bind water, increasing faecal bulk, and reducing transit time.These fibres are present in cereals brans including oats and wheat bran and can be helpful in reducing constipation (1).
Additional properties of fibre, such as viscosity, may be important characteristics in terms of physiological benefits. Viscous fibres are those that have gel-forming properties in the intestinal tract.
Some dietary fibres can also be classified as prebiotics.Prebiotics are defined as “selectively fermented ingredients that result in specific changes, in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health” (8).
HEALTH BENEFITS OF FIBRE
Today, dietary fibres are known to be protective against:
· certain gastrointestinal diseases
· colon cancer
· breast cancer
· gastroesophageal reflux disease
· duodenal ulcer
· type 2 diabetes
· cardiovascular diseases and
· coronary heart disease
High intakes of dietary fibre may reduce absorption of some minerals and drugs (1). Several studies have shown soluble dietary fibre to inhibit absorption of the levothyroxine (thyroid medication), and it is therefore recommended to take oral levothyroxine 1 hour prior to food intake (7).
Phytic acid has a strong binding affinity to minerals such as calcium, zinc, magnesium and iron (7). It is often referred to as antinutrient because humans lack enzyme phytase in their digestive tract to break it down. Phytic acid is naturally found in beans, but you can easily lower the amount you consume by soaking or sprouting the beans.Soak beans for a minimum of 12 hours to maximize the amount of phytic acid lost, suggests the Weston A. Price Foundation. Drain and rinse the beans several times during soaking to get rid of the phytic acid that has leached into the water. Do not use the soaking water for cooking. When beans sprout, an enzyme is activated that breaks down phytic acid and causes its levels to go down.
HOW TO GET MORE FIBRE INTO YOUR DIET
First of all, it is important to get fibre from a variety of sources. Foods that are high in fibre contain more than just fibre. Eating too much of one type of food may not help you achieve a healthy balanced diet.
Introduction of more fibre should be done gradually to avoid any negative outcomes. After a large increase in the amount of fibre in the diet, some people experience symptoms such as abdominal distension, wind and discomfort. However, the large intestine and gut bacteria gradually adapt to the increased intake and symptoms usually decrease (1).
It is important to drink enough water,especially with high fibre diet. Increasing fibre may cause abdominal discomfort and constipation IF not accompanied by enough fluid.
It is always better to add fibre to the diet from food sources rather than from fibre supplements.Fibre supplements may appear to be a healthy option to increase fibre intake, but clinical evidence supports that most fibres in supplements do not provide any of the health benefits associated with a high‐fibre diet (10).
It is worth mentioning that studies show strong links between FODMAPs (Fermentable Oligo-, Di- and Mono-saccharides And Polyols) and digestive symptoms like gas, bloating, diarrhoea, constipation and stomach pain. If you are experiencing any of these symptoms, it is a good idea to seek a help of a Registered Nutritional Therapist, as some people may benefit from low-FODMAP diet.
1. Always keep the skin on vegetables; buy organic when possible (look for Dirty Dozen list and visit the Environmental Working Group) or wash well*
2. Include plenty of vegetables with meals
3. Snack on fresh fruit, vegetable sticks, rye crackers, oatcakes and unsalted nuts or seeds (2)
4. Try meat free days and instead include protein and fibre rich legumes
5. Add beans, lentils or chickpeas to stews, curries and salads (2)
*Rinsing produce under running water generally removes less then half of the pesticide residue. To make your own pesticide-reducing bath, add one part salt to nine parts water. Make sure to rinse off all the salt before eating.
FIBRE RICH FOODS:
· Oats: 16.5 g per cup, raw
· Split Peas: 16.3 grams per cup, cooked
· Lentils: 15.6 grams per cup, cooked
· Black Beans: 15 grams per cup, cooked
· Mung beans: 15 grams per cup, cooked
· Lima Beans: 13.2 grams per cup, cooked
· Chickpeas: 12.5 grams per cup, cooked
· Almonds: 12.5 g per 100 grams, raw
· Artichokes: 10.3 grams per medium vegetable, cooked
· Buckwheat: 10 grams per 100 grams, raw
· Coconut flour: 10 grams per ¼ cup
· Peas: 8.8 grams per cup, cooked
· Millet: 8.5 grams per 100 grams, raw
· Broccoli: 5.1 grams per cup, boiled
· Raspberries: 8 grams per cup, raw
· Blackberries: 7.6 grams per cup, raw
· Avocados: 6.7 grams per half, raw
· Bran Flakes: 7 grams per cup, raw
· Pearled barley: 6 grams per cup, cooked
· Chia seeds: 5.5 grams per tablespoon
· Pears: 5.5 grams per medium fruit, raw
· Apples: 4.4 grams per medium fruit, raw with skin
· Brussels Sprouts: 4.1 grams per cup, boiled
· Sweet potato: 3.8 grams per 1 medium, raw
· Apricots: 3.1 grams per cup
Written by:Jana Papajova
1. BNF. (2018). ‘Dietary fibre’. (Online). Available at: htps://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/dietary-fibre.html.
2. NHS. (2018). ‘How to get more fibre into your diet’. (Online). Available at: https://www.nhs.uk/live-well/eat-well/how-to-get-more-fibre-into-your-diet/#tips-to-increase-your-fibre-intake.
3. Slavin, J. (2013). ‘Fiber and Prebiotics: Mechanisms and Health Benefits’. Nutrients,5(4), pp.1417-1435.
4. Frost, G. Sleeth, M. Sahuri-Arisoylu, M. et al. (2014). ‘The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism’. Nature Communications,5, p.3611.
5. Gonçalves, P. Araújo, J. and Di Santo, J. (2018). ‘A Cross-Talk Between Microbiota-Derived Short-Chain Fatty Acids and the Host Mucosal Immune System Regulates Intestinal Homeostasis and Inflammatory Bowel Disease’. Inflammatory Bowel Diseases,24(3), pp.558-572.
6. Wong, J.M. de Souza, R. Kendall, C.W. (2006). ‘Colonic health: fermentation and short chain fatty acids’. Journal of Clinical Gastroenterology, 40(3), pp.235-43.
7. Maćkowiak, K. Torlińska-Walkowiak, N. and Torlińska, B. (2016). ‘Dietary fibre as an important constituent of the diet’. Postępy Higieny i Medycyny Doświadczalnej, 70, pp.104-109.
8. Gibson G.R. Scott, K.P. Rastall, R.A. et al. (2010). ‘Dietary prebiotics: current status and new definition.’ Food Science,7(1), pp.1-19
9. Otles, S. and Ozgoz, S. (2014). ‘Health effects of dietary fiber’. Acta Scientiarum Polonorum. Technologia Alimentaria, 13(2), pp.191-202.
10. Lambeau, K. and McRorie, J. (2017). ‘Fiber supplements and clinically proven health benefits’. Journal of the American Association of Nurse Practitioners, 29(4), pp.216-223.