Health · Nutrition · Fibre · Dietary Fibre
The Nutrition Fundamentals: Understanding Dietary Fibre
What is Dietary Fibre?
Dietary fibre, often called “roughage,” is a complex carbohydrate in plant foods. It includes non-starch polysaccharides, resistant starches, and cellulose. Unlike other carbohydrates, our bodies lack the enzymes to digest fibre fully.
The Definition Dilemma
Defining dietary fibre has been quite a challenge. It’s not a single chemical entity; different fibre types can have various health benefits. In 2009, an international consensus defined dietary fibre as:
Edible carbohydrate polymers occur naturally in food.
Carbohydrate polymers obtained from food raw materials through physical, enzymatic, or chemical means with proven health benefits.
Synthetic carbohydrate polymers with demonstrated health benefits.
In simpler terms, dietary fibre includes edible carbohydrate polymers with proven health benefits supported by scientific evidence.
Types of Fibre
Traditionally, fibre was categorised as soluble and insoluble. Soluble fibre dissolves in water, while insoluble fibre doesn’t.
For simplicity, let’s stick with these terms.
Soluble Fibre (Dissolves in Water)
Soluble fibre resists digestion in the mouth, stomach, and small intestine, reaching the large intestine, fermented by beneficial gut bacteria. This fermentation produces short-chain fatty acids, such as butyric and acetic acids. Soluble fibre includes:
Gums are used in foods to add texture and extend shelf life.
Pectins are slightly acidic and aid mineral absorption.
Inulin is a prebiotic that feeds good gut bacteria.
The benefits of soluble fibre include reduced cancer risk, lower LDL (harmful) cholesterol levels, and stabilised blood sugar.
Insoluble Fibre
Insoluble fibre resists digestion and passes through the digestive system intact. Its primary role is to help transport other foods and liquids by absorbing water and adding bulk to stools. It includes lignin, cellulose, and hemicellulose. Benefits include preventing constipation and reducing the risk of certain diseases.
Sources of Fibre
To get a balanced dietary fibre intake, consume various fibre-rich foods, as different fibre types are found in varying proportions.
Here’s a breakdown:
Cellulose : Found in grains, vegetables, fruits, nuts, and cereal bran.
Hemicellulose : Present in cereal grains, vegetables, fruits, legumes, and nuts.
Lignin : Associated with woody components like celery and the outer layers of cereal grains.
Beta-glucans: Found in oats and barley cell walls.
Pectins: Common in fruits, vegetables, legumes, nuts, and potatoes.
Gums & Mucilage: Used as gelling agents, thickeners, and stabilizers. Gums come from seeds and seaweed extracts, while mucilages originate from psyllium seeds.
Resistant Starch: Present in legumes, potatoes, and cereal grains.
Oligosaccharides: Include fructooligosaccharides and galactooligosaccharides found in onions, chicory, and Jerusalem artichokes.
Micro Components: Waxes, cutin, and suberin are found in cereal grains.
How Much Fibre Should You Eat?
The recommended daily intake for fibre is at least 25g for women and 30g for men, with proportionally less for children (18-28g depending on age).
However, most Australians fall short of this goal. The Australian Health Survey revealed that the average Australian adult consumes only about 20-25g of fibre daily, well below the recommended amounts.
In Australia, dietary fibre is measured using the AOAC method (Association of Official Analytical Chemists), which includes non-starch polysaccharides, resistant starches, and lignin. The Australia New Zealand Food Standards Code sets criteria for products labeled as “source of fibre” (at least 2g per serve) or “good source of fibre” (at least 4g per serve).
In Conclusion
Dietary fibre is essential to a healthy diet, offering numerous health benefits. While reaching the recommended daily intake is vital, focusing on whole, unprocessed foods rich in fibre can naturally provide what you need. Incorporating fruits, vegetables, and legumes into your diet ensures you get plenty of fibre.
Understanding dietary fibre empowers you to make better choices for your health. So, make fibre a part of your daily routine, and enjoy its benefits to your overall well-being.
Do you have any questions or thoughts on dietary fibre? Share them in the comments below! Your input can help others on their journey to a healthier lifestyle.