Unlocking the Power of Fibre: Why Intrinsic Dietary Fibres Matter for Gut Health
Despite the abundance of plant-based foods, many of us are still missing out on an essential component for health: dietary fibre. Fibre-rich plants comprise around 80% of foods, but most people do not achieve recommended intakes (more than 25 g per day), largely due to the prevalence of refined, low-fibre products that are affordable and energy-dense but nutrient-poor.
Low dietary fibre intake is linked to a higher risk of disease (cancer, cardiovascular disease, obesity, and type 2 diabetes) and premature (before 75 years) death. Therefore, increasing fibre consumption is crucial for public health. However, not all dietary fibres are created equal, and understanding these differences is key to improving gut and overall health.
What are Intrinsic Dietary Fibres?
Intrinsic dietary fibres are the non-digestible components found naturally within plant foods, such as fruits, vegetables, grains and legumes. While these whole plant foods provide intrinsic fibres, many food products lose their intrinsic fibre content during processing. As a result, isolated fibres are now added back to many processed foods to boost content and improve fibre intake. However, unlike intrinsic fibres, these added fibres are lacking the functional and complex structure of whole foods, which offer additional benefits.
For a list of dietary fibres found in whole foods see at the end of this blog.
What are the additional benefits of intrinsic fibres?
The benefits of intrinsic dietary fibres were investigated by Marie-Luise Puhlmann during her her PhD research, which she successfully defended at Wageningen University (NL) on 9th October 2024.
Dr Puhlmann aimed to better understand the role of intrinsic fibres using chicory root, which is particularly rich in these components and, notably, inulin. Her research showed that intrinsic fibres are less accessible to gut microbiota than added fibres. This results in a slower and more sustained microbial breakdown of the naturally-occurring fibres throughout the length of the gastrointestinal tract, leading to an increased production of short chain fatty acids.
These apparently small differences significantly impact gut and overall metabolic health. Consumption of dried chicory roots positively altered gut microbiota composition, which was associated with improved bowel function and better glucose control and insulin sensitivity. Her findings suggest intrinsic fibres not only support gut health but have a role in regulating metabolism and preventing chronic diseases such as type 2 diabetes.
Future research and takeaways
This research raises questions about current food processing. Rather than re-incorporating fibres, we should be exploring how processing can safeguard the plant matrix to maintain the beneficial properties of intrinsic fibres. Additionally, re-classifying dietary fibre as essential (i.e., absence is associated with a dietary deficiency) would support promotion of its benefits, encouraging individuals to choose whole or minimally processed foods.
Dr Pulhmann concluded, “Ultimately, insights [from this thesis] will help raise awareness that dietary fibres in their intrinsic form enhance their health benefits and are essential to consider in efforts to address the fibre gap”. To read more in the topic: Back to the chicory roots: Dietary fibers rediscovered to benefit human health — Research@WUR
There are several types of dietary fibres:
Soluble fibres: Absorbs water to form a gel-like substance in the digestive system. It can help lower cholesterol levels and regulate blood glucose. Sources include oats, legumes, apples, and citrus fruits. Includes:
- Inulin: found in various plants, such as chicory root and garlic. It acts as a prebiotic, promoting the growth of beneficial gut bacteria.
- Resistant Starch: found in legumes, whole grains, and potatoes. Cooking and cooling starches, such as rice, pasta, and potatoes, can increase the amount of resistant starch.
- Wheat Dextrin: derived from wheat, marketed as gluten-free, that is used to boost fibre content in various foods.
- Beta-Glucans: found in oats and barley that is known for its cholesterol-lowering effects and immune-boosting properties.
- Oligofructose: found in foods such as artichokes, garlic, and onions. It acts as a prebiotic and helps stimulate the growth of beneficial gut bacteria.
- Pectin: mainly found in fruits, particularly apples and citrus. It has been linked to lower cholesterol levels. It also has insoluble properties and helps with digestive health.
Insoluble fibres: Do not dissolve in water and adds bulk to stool, helping to prevent constipation. Found in whole grains, nuts, and the skin of fruits and vegetables. Includes:
- Cellulose: A form of insoluble fibre that consists of long chains of glucose. It provides structure to plant cell walls.
- Hemicellulose: A complex carbohydrate found in plant cell walls, differing from cellulose in that it has a branched structure composed of various sugars, providing structural support while being more soluble and easier to digest than cellulose.
- Lignin: A complex, insoluble fibre that differs significantly in structure from other types of dietary fibre. It is found in the woody parts of plants and contributes to their rigidity.