Fibre-rich diet may help maintain weight, gut health

Trying to watch your waistline this holiday season? You may want to pay more attention to the diet of your gut bacteria, according to scientists who suggest that a fibre rich diet can influence weight gain, blood sugar and colon health.

It is not just calories that matter in a healthy diet – it is fibre that resists digestion by the body but is readily eaten by bacteria in the gut, researchers said.

Research with mice, published in the journal Cell Host and Microbe, help shed light on how and why fibre has such a powerful effect on the entire body.

“Once the mechanism is understood, it can be exploited in different ways to promote health,” said Andrew Gewirtz, from Georgia State University in the US.

“This will allow ways to modify diets to maximise those benefits,” Gewirtz said.

Fibre in its various forms is found in fruits, legumes, vegetables, and whole grains. So-called Western diets, which are high in fats and sugars but low in fibre, have been linked to an increased risk of inflammatory bowel diseases, weight gain, and diabetes.

“It is becoming increasingly clear that the average person’s fibre intake in a Western country has drastically reduced over the past few decades,” said Fredrik Backhed, from the University of Gothenburg in Sweden.

Both studies started by feeding a group of mice a diet that was extremely low in fibre. The low-fibre diets rapidly led to weight gain, high blood sugar, and insulin resistance in the mice.

The study found that mice developed problems with the protective mucus layer in the colon after just 3-7 days of eating the low-fibre diet. This mucus layer became more penetrable and bacteria encroached upon the epithelial cells of the colon.

Another study observed that the colons of mice on the low-fibre diet shrank significantly in thickness. Not only did large amounts of gut bacteria die off after mice ate a low- fibre diet, mice developed unhealthy imbalances of different gut bacteria strains.

“These papers show the importance of the inner mucus layer in separating bacteria and human host. It nicely illustrates how dynamic and quickly this responds to diet and bacterial alterations,” said Gunnar C Hansson, from the University of Gothenburg in Sweden.

“Both our paper and the Backhed paper are essentially reaching the same conclusion that the lack of fibre results in bacteria encroaching into the mucus layer, and those bacteria are promoting low-grade inflammation, contributing to metabolic syndrome,” said Gewirtz.

“Diets that lack fibre alter the bacterial composition and bacterial metabolism, which in turn causes defects to the inner mucus layer and allows bacteria to come close, something that triggers inflammation and ultimately metabolic disease,” said Hansson.

“It is not enough just to add fibre to your diet; it also depends on which bacteria you carry,” Gewirtz said.

This likely means more study is needed before fibre supplements can be used as a treatment.

“Simply enriching processed food with purified fibres might offer some health benefits, but we’re not ready to recommend it until we understand more of the very complex interplay between food, bacteria, and host,” Gewirtz said.