Scientists propose new fiber classification to optimize gut health and address global fiber gap

By ljdevon // 2025-03-22

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Researchers propose a new fiber classification system based on five key features: backbone structure, water-holding capacity, structural charge, fiber matrix, and fermentation rate.
The framework aims to help consumers, clinicians, and food technologists tailor fiber intake to address specific health issues, such as colonic health, blood sugar control, and cholesterol reduction.
Global fiber intake is alarmingly low, with Americans consuming only 12-14 grams per day and Europeans 18-24 grams, far below the recommended 28-42 grams.
The gut microbiome plays a critical role in fiber fermentation, producing short-chain fatty acids (SCFAs) that support overall health, including immune function and cancer prevention.
The modern Western diet, low in fiber and high in processed foods, has been linked to gut dysbiosis and the rise of chronic diseases like obesity, diabetes, and cancer.

In a groundbreaking study published in Food Research International, Australian researchers from RMIT University have redefined how dietary fibers are classified, moving beyond the simplistic soluble and insoluble categories. This new framework aims to provide a more nuanced understanding of how different fibers interact with the human body, particularly the gut microbiome, to address specific health concerns. With global populations falling short of recommended fiber intake, this research could revolutionize personalized nutrition and help close the "fiber gap" that plagues modern diets.

The fiber gap: a global health crisis

Dietary fiber, found in fruits, vegetables, beans, and whole grains, is one of the most vital nutrients for human health. It aids digestion, supports weight management, regulates blood sugar, improves heart health, and even helps prevent cancer. Yet, despite its importance, most people worldwide are not consuming enough. According to Professor Raj Eri, a food scientist at RMIT University, "Every single population surveyed, including Europe and the USA, has a deficiency of fiber." The recommended daily intake of fiber is 28-42 grams, but Americans average only 12-14 grams, while Europeans consume slightly more at 18-24 grams. This "fiber gap" is a significant public health concern, given the nutrient's role in preventing chronic diseases and supporting gut health.

Beyond soluble and insoluble: a new framework for fiber

Traditionally, dietary fibers have been classified as either soluble or insoluble based on their ability to dissolve in water. Soluble fibers, such as those found in oats and apples, are fermented in the gut and can lower cholesterol and regulate blood sugar. Insoluble fibers, like those in wheat bran, promote regularity but are less likely to ferment. However, this binary classification fails to capture the complexity of how different fibers interact with the body. The RMIT team's new framework identifies five key features of fiber: 1. Backbone structure: The molecular arrangement of the fiber. 2. Water-holding capacity: How much water the fiber can absorb. 3. Structural charge: The electrical properties of the fiber. 4. Fiber matrix: The physical structure of the fiber. 5. Fermentation rate: How quickly the fiber is broken down by gut bacteria. "By starting with these key active features, we can more accurately describe each fiber's health impacts," said Christo Opperman, lead author of the study and a PhD candidate at RMIT. "For example, if you want to promote colonic health, you can identify a fiber with properties that align with your desired outcome, such as a high fermentation rate."

The microbiome: fiber's secret ally

The human gut microbiome, home to trillions of bacteria, plays a crucial role in breaking down dietary fiber. These microbes produce SCFAs like acetate, propionate, and butyrate, which provide energy for colon cells, regulate inflammation, and support immune function. Butyrate, in particular, has been linked to reduced cancer risk and improved gut health. "Fermentation of dietary fiber occurs predominantly in the colon, producing metabolites that are essential for overall health," explained Opperman. "However, not all fibers are created equal. Some are fermented quickly in the proximal colon, while others provide benefits further down in the distal colon, where most colorectal cancers occur." The new classification system aims to help researchers and consumers understand which fibers are best suited for specific health goals. For instance, fibers with a high fermentation rate may be ideal for promoting gut health, while those with high water-holding capacity could aid in weight management by increasing satiety.

The modern Western diet is stripped of fiber, beckoning chronic disease

The modern Western diet, characterized by high levels of refined sugars, sodium, and trans fats, has been linked to a decline in fiber intake and a rise in chronic diseases. During the mid-20th century, as processed foods became more prevalent, fiber-rich whole foods like fruits, vegetables, and whole grains were increasingly replaced with refined alternatives. This shift has contributed to gut dysbiosis—an imbalance in the gut microbiome—and the proliferation of non-communicable diseases such as type 2 diabetes, obesity, and cancer. Dietary fiber was first formally defined in 1953 by Hipsley, who described it as the indigestible parts of plant cell walls. Since then, the definition has evolved, but the classification system has remained overly simplistic. The RMIT team's new framework represents a significant step forward in understanding the diverse roles of fiber in human health. The researchers hope their new classification system will inspire food technologists to develop targeted fiber-rich products and encourage consumers to prioritize fiber in their diets. "Our framework is an essential step in addressing the fiber gap," said Eri. "By understanding the specific properties of different fibers, we can create diets that are not only healthier but also more personalized." Sources include: ScienceDaily.com RMIT.MIT.edu.au ScienceDirect.com