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Researchers at RMIT University in Australia have unveiled a new study proposing a more nuanced classification of dietary fibres to drive health-targeted food products.

Dietary fibres, which can be found in fruit, vegetables, beans and whole grains, are vital components for human health. They aid digestion, weight management, blood sugar control, heart health, cancer prevention and more.

However, RMIT University food scientist Raj Eri believes consumer advice on how best to use fibres for these health benefits is lacking.

Eri commented: “Quite like how different medicines target different conditions, so too do different types of fibres. For example, apples and bananas are both rich in dietary fibre, but the fibre in each works very differently.”

The team’s research, published in Food Research International, proposes a new fibre classification based on five key features: backbone structure, water-holding capacity, structural change, fibre matrix and fermentation rate. It aims to help people to understand which types of fibre they should consume to address certain health concerns.

Christo Opperman, the study’s lead author and RMIT PhD candidate, said that by starting with the key active features of fibre in a ‘bottom-up approach,’ the health impacts of each fibre can be more accurately described.

“Our new classification looks at different properties of fibre, like how well it holds water, its structure, how quickly it ferments, and its overall make-up,” he explained. “This helps us predict how eating fibre in foods or supplements affects your body and gut bacteria.”

“For example, suppose you want to promote colonic health. In that case, you identify a fibre’s properties as defined by the bottom-up approach, which align with your desired outcome – in this case fermentation rate.”

He added that while apple and fibre supplements like wheat dextrin were considered similar because they’re both soluble fibre, the team’s new approach shows aple fibre is better for the gut because it holds onto water, sugar and cholesterol well.

“This classification also helps us understand which bacteria in the intestine will grow by digesting these fibres, which is important for tackling certain health issues.”

Opperman said that applying the new framework could assure consumers, dieticians, clinicians and food technologists that they are receiving their desired health effects rather than relying on a “vague guessing game”.

The RMIT team has taken 20 different types of fibres and studied how they interact specifically with the gut microbiome.

Currently, classification of dietary fibres groups them into soluble and insoluble fibres, based on whether they dissolve in water. Insoluble fibres are seldom fermented in the large intenstine and can promote bowel health and regulatiry, while soluble fibres are more readily fermented and can reduce cholesterol, glucose absorption and food cravings. However, insoluble fibres can also rapidly ferment and reduce glucose absorption.

“Despite our evolving understanding of how central different types of fibre are to nurturing a healthy gut biome, our dietary fibre classifications remain simplistic between broad categories of soluble and insoluble types,” Eri said.

“This binary classification of soluble and insoluble insufficiently captures the diverse structures and complex mechanisms through which dietary fibres influence human physiology.”

Eri noted there is already strong interest in how to better integrate fibre into diets. While recommended daily fibre intake is 28-42g per day, research showed American consumers only get 12-14g per day on average, and Europeans 18-24g per day. In countries surveyed, every single population had a deficiency of fibre, Eri pointed out, emphasising that this is “extremely worrying” given that fibre is one of the most important nutrients.

The team believes its research could have a huge impact on this, providing a thorough framework that could address the fibre gap. The researchers are now planning to investigate how a specific type of fibre (based on the new classification) modulates the microbiota, and how such knowledge can be utilised for specific health applications.