Fibre - Everything you need to know
What is it?
Fibre is the edible parts of plants and carbohydrate-rich foods that are resistant to digestion and absorption into the body (1). Dietary fibre is found in rich sources in fruits, vegetables, and whole grains (2). These whole foods not only provide essential vitamins and minerals but also offer different types of fibre that contribute to various health benefits (2). Fibre’s resistance to digestion is due to it’s unique molecular structure, which consists of long chains of glucose molecules. Unlike other carbohydrates that our body breaks down into glucose for energy, fibre passes through the digestive system largely intact, allowing it to play a different role in our digestive health (3).
There are two main types of fibre: soluble and insoluble (3-4).
Soluble Fibre:
Dissolves in water and forms viscous gels in the small intestine.
Increases the transit time through the digestive tract, which delays gastric emptying.
Bypasses the digestion process in the small intestine and is easily fermented by microflora in the large intestine.
Main sources include fruit and vegetables, oats, psyllium, pulses, and Metamucil.
Insoluble Fibre:
Does not dissolve in water and undergoes only very limited fermentation in the large intestine.
Increases the bulk of the stool, aids in the excretion of bile acids, and decreases intestinal transit time.
Main sources are cereals and whole-grain products such as bran and rice bran.
Health Benefits
There are numerous reported health benefits of fibre. Unlike many aspects of nutrition that are incredibly nuanced and contextual, this one appears to be pretty straightforward: most people should be eating more fibre as it’s great for our health!
Cardiovascular Health: Evidence suggests that fibre intake is associated with a decreased risk of cardiovascular disease and coronary heart disease (5).
Cancer Prevention: Fibre is associated with a decreased risk of multiple cancers (6), particularly colorectal cancer (7).
Overall Longevity: High fibre intake is even associated with a decreased risk of all-cause mortality, meaning it can potentially reduce the risk of dying from any cause (8).
Possible Mechanisms for These Health Benefits
There are several potential mechanisms through which fibre may confer these health benefits:
Cholesterol Lowering: Fibre inhibits cholesterol synthesis and reduces blood cholesterol levels. By binding to bile acids and cholesterol in the intestine, fibre helps remove them from the body, which in turn lowers blood cholesterol levels (8).
Blood Pressure: Regular intake of fibre can contribute to lower blood pressure, which is a crucial factor in reducing the risk of cardiovascular diseases (8).
Satiety and Weight Management: Fibre promotes satiety, helping to regulate energy intake and weight. Foods high in fibre take longer to chew and digest, which can help you feel full longer and prevent overeating (8).
Insulin Sensitivity: Fibre improves insulin sensitivity and slows glucose absorption. This helps to maintain stable blood sugar levels, which is particularly beneficial for individuals with diabetes or those at risk of developing the condition (8).
Binding Bile Acids and Carcinogens: Fibre aids in the binding of bile acids and potential carcinogens, facilitating their excretion and reducing their potential to cause harm in the digestive tract (8).
Gut Health: Fibre offers significant benefits to gut health. It promotes a healthy balance of gut bacteria, which play a vital role in maintaining digestive health and supporting the immune system (3).
Importantly, a high-fibre diet is often rich in other beneficial and health-improving compounds such as antioxidants and micronutrients that are widely available in fruits, vegetables, and whole grains (5). These compounds work synergistically with fibre to enhance overall health.
How Much to Eat?
The Australian Nutrient Reference Values recommend 30 grams per day of fibre for adult men and 25 grams per day for adult women. These are general recommendations for the population to remain healthy, but there may be benefits to aiming for a lower or higher amount depending on your individual circumstances.
Here’s a simple list of food to show what 30+ grams of fibre could look like through the day:
Oats: 1 cup cooked (4 grams fibre)
Chia Seeds: 1 tablespoon (5 grams)
Raspberries: 1/2 cup (4 grams)
Apple: 1 medium with skin (4 grams)
Whole Grain Bread: 2 slices (6 grams)
Avocado: 1/2 medium (5 grams)
Brown Rice: 1 cup cooked (3.5 grams)
Adjusting portions slightly can help you tailor your intake to meet your specific needs.
Although fibre is widely accepted to be great for health, it is generally recommended that if you are aiming to increase your fibre intake, you do it gradually. This allows your digestive system time to adapt to the higher intake and can help prevent discomfort such as bloating and gas.
Additionally, some individuals may need to stick to a low-fibre diet due to specific health conditions. It’s always best to consult with a dietitian or health professional if you have any concerns or health issues that might affect your fibre intake.
By understanding the types of fibre, the health benefits they offer, and the sources from which to get them, you can make informed choices that support your overall health and well-being. Including a variety of fibre-rich foods in your diet is a simple yet powerful way to improve your health and protect against chronic diseases.