Plant based fibre

Emerging research is demonstrating the many roles and benefits of plant-based fibre; in particular its specific relationship with our intestinal microbiota and how this can impact our overall health.

Fibre or ‘roughage’ is the carbohydrate portion of plant-based foods that passes through the small intestine undigested. There are two basic types; soluble fibre, which dissolves in water and forms a smooth gel in the small intestine before passing to the large intestine – and insoluble fibre, which is not soluble in water and works as a type of ‘roughage’ passing through the intestines undigested. Most plant-based foods contain varying quantities of both types of fibres.
Most fruits, vegetables, seeds and grains have insoluble fibre on the rough skin surface, and soluble fibre on the inner starch or pulp. Grain-based foods are generally higher in insoluble fibre (due to the dense outer shell) but much of this is removed with industrial milling techniques.
Since the introduction of modern agricultural practices, the quantity and composition of fibre has changed so that we are not only consuming less fibre, but more importantly less types of fibre which are fermentative and able to exert beneficial effects on our digestive system.

Our digestive system is home to approximately 100 trillion bacteria; tiny bugs which inhabit our skin surface, digestive tract, mouth and salivary glands.
There are roughly 500 different species of bacteria in our intestinal tract and these bacteria play an important role in healthy digestive function, they also regulate metabolism and play host to up to 75% of the immune system.
The composition of these bacterial populations is particularly important; a good balance of beneficial bacteria is essential for a healthy immune system, protection against harmful microorganisms and our overall ability to digest food and absorb nutrients.

Research has shown that the bacterial composition of our digestive tracts are now linked to a large number of Western diseases, including autoimmune diseases, type 2 diabetes and obesity. As an example, several studies have shown that the composition of the gut flora differs in people who are overweight and obese compared to those with a healthy body weight. This indicates that a healthy gut microbiota may assist in the achievement and maintenance of a healthy body weight.

Recent research has shed light on factors that can impact the composition and quantity of beneficial microflora in the digestive tract. In particular, the role of fibre as a food source for health-promoting bacteria. Soluble fibre has been shown to act as a ‘pre-biotic’; meaning a food for probiotic bacteria. Regular consumption of soluble fibre can promote a shift in the population of gut microbiota toward different types of beneficial bacteria.

The proposed mechanism is that certain types of fibre feed different strains of health-promoting bacteria such as the lactobacillus and bifidobacterium strains.
Basically, the colon works like a fermentation factory; microbes feed on the fibre and make the environment more acidic and resistant to pathogens.
The conversion of fibre to energy also promotes the production of short chain fatty acids; these fatty acids can have an anti-inflammatory effect on the gut lining and reduce gut permeability.

Resistant starch is another type of fibre and works in a similar manner to soluble fibre. It ‘resists’ digestion in the small intestine and makes its way to the large intestine where it interacts with health-promoting bacteria to produce a number of beneficial metabolites such as butyric acid. Resistant starch is found in potatoes, fresh (greenish) bananas and several grain-based foods.

Less than half of Australians currently consume the recommended fibre intake of 25-30g/day. Not only are Australians not consuming enough fibre, but the types of fibre that people are choosing to consume are changing too. Less fibre is consumed in the form of fresh fruit and vegetables, whereas the consumption of grain-based and fortified fibre foods has increased exponentially. 

Food companies have cottoned on to the public interest in fibre consumption and have since started fortifying their foods with synthetic fibre additives, a minimum quantity of fibre (of any form) allows for a nutrient labelling claim, and subsequent increase in sales.

Thankfully, increasing your fibre intake could be as simple as adding a few extra servings of fresh fruit and vegetables on your plate each day. Fibre intake is important, but getting the right combination of health-promoting fermentative fibres in the diet is imperative for good digestion and overall health.
These fermentative fibres are easily found in whole, unprocessed foods and home-grown fruit and vegetables.