The GI Files – Part 3

Let’s zoom in on dietary fibre in the GI system

by Jada-Virginia Surpin

One of the key points highlighted by Dr Patel in our recent podcast along with other world class gastrointestinal specialists, is the importance of dietary fibre. The interview discussed the way fibre strengthens the walls of the bowel, which is one of the many benefits of fibre to the GI system. In this blog, I aim to elaborate on these benefits as well as the consequences of an insufficient intake of fibre. Furthermore, I will categorise the most common sources of fibre so you can gain a comprehensive oversight of your daily fibre intake – plus I will highlight Dr Patel’s practical tips which will help you even further in this direction.

The key role of fibre in digestion

Dietary fibre is needed for normal, functioning digestion. What we typically call dietary fibre is cellulose, a highly fermentable beta-glucan originating in plant cell walls; which humans are unable to digest and also has a very rigid structure. These two characteristics mean that cellulose passes directly out of the digestive system and, I believe, aids excretion through the back passage.

A nutrition research review article has found that an increase in fibre intake may decrease the incidence of constipation whilst children with sufficient dietary intake of fibre are less likely to develop constipation than those with a low intake of dietary fibre.

Since fibre is the “substrate” for bowel muscle exercise as stated by Dr Patel, successful excretion certainly depends on fibre intake, as well as decreasing the lumpy and hard texture of stool.

Regulating our appetite

A 7-week experiment published in the British Journal of Nutrition using sixteen healthy adult dogs determined that a diet rich in highly fermentable fibre significantly decreased appetite. This could also indicate a relationship between dietary fibre and hormonal control of diet.

The Journal of Functional Foods has recently found that cellulose from Hibiscus sabdariffa and Agave Tequilana decreased body weight and obesity in rats.

These two plants were successfully investigated as a treatment for obesity in animals, therefore, it would be interesting to see the result in human trials. Furthermore, the evidence may suggest a causal link between fibre and appetite and therefore long-term obesity prevention.

It could be that fibre simply provides a psychological sense of fullness and satisfaction due to its rigid and bulky nature, preventing overeating. Therefore, as Dr Patel confirms, although often bread causes bloating and GI upset (THG comment: many people are intolerant to gluten, which can cause digestive distress. The nature of modern bread is such that is considered to be an ultra-processed food and best avoided. For those wishing to include bread who don’t have a gluten intolerance or aren’t coeliac try 48 hour fermented sourdough rye bread), it cannot be said to cause weight gain in and of itself, although there are better sources of fibre and excess highly processed carbohydrates do cause weight gain.

Another way to regulate your appetite is to eat at a reasonable pace, you should be chewing every mouthful so that your stomach has the time to communicate with your brain via the vagal nerve, triggering the release of the hormone leptin, which is one of several hormones responsible for appetite control. In other words, if you eat too quickly, your brain doesn’t have the time to sense and regulate your food intake.

Food for your gut bugs

Recent studies show that overall diet affects the composition of the gut microbiome. When fibre is investigated specifically, it is believed to nourish beneficial gut bacteria bacteria. The healthy gut microbiome which results was found to have key roles in the function of the digestive tract, supporting the gut immune system and the fermentation of nutrients. Furthermore, it has been found that when the gut microbiome and bacteria composition is disturbed, the incidence of colorectal cancer, inflammatory bowel disease and metabolic syndrome increases. The cancer link was determined by comparing colorectal cancer patients’ gut microbiota with those in a healthy control group.

Common sources of high-fermentable fibre

  • Apple
  • Raspberries
  • Oats
  • Seaweed
  • Kidney beans
  • Barley
  • Nuts
  • Pumpkin seeds
  • Cereal bran

High-fermentable fibre (HFF) is believed to confer more health benefits than low-fermentable fibre (LFF) and the positive effects of Beta-Glucans such as cellulose have been extensively investigated.

This list of high-cellulose foods will help you meet the daily fibre requirements of 25-35g, showing you how many grams of cellulose each item contains.

For more information on eating a fibre-rich diet check out the ANH International Food4Health guidelines.


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