Five reasons to eat fibre-rich foods
- 21 hours ago
- 4 min read
You may have heard that eating food rich in fibre is good for you. But why? Fibre cannot be broken down like a typical carbohydrate. It passes right through the colon – so what’s the use? Maybe we can do without all that extra chewing!
We actually tried that experiment with ultra-processed food and it has not turned out well. When we look at our ancient ancestors, they ate a lot of fibre-rich food and our bodies evolved to thrive on it. Not least because our microbiome – the trillions of bacteria in our intestines – has evolved alongside us. Many of these ‘good’ bacteria need fibre to survive.
So here are the five main reasons to eat fibre-rich food.
1. It prevents constipation
There are two types of dietary fibre: soluble and insoluble. Insoluble fibre, such as the cell walls in plants, does not dissolve in water or gastrointestinal fluids. It passes through the colon largely unchanged. It adds bulk to stool and helps it pass more easily through the colon. It also helps regulate how much fluid is retained in the stool, which supports regular and comfortable bowel movements.
2. It supports your overall health by maintaining gut species diversity
Soluble fibre behaves differently. It dissolves in both water and gastrointestinal fluids, forming a gel-like substance that can be fermented by the colon’s bacteria. Soluble fibres are critical because they serve as food for your microbiome. Through his research, Dr. Rob Knight, creator of the American Gut Project, found that eating at least 30 different plants per week is the strongest predictor of gut diversity. The more plants we eat, the more diverse and healthier our bacteria are, and by extension, the better we feel. A diverse microbiome is linked to everything from improved mood to a stronger immune system. Essentially, a more varied diet leads to a more robust internal ecosystem.
3. It decreases inflammation
When gut bacteria ferment fibre in the large intestine, they produce energy along with short-chain fatty acids or SCFAs. These compounds – primarily acetate, propionate, and butyrate – are more than just byproducts. They act as messengers between your gut and your immune system. They function as signalling molecules that train the immune system to remain calm instead of overreacting to every stimulus.
For instance, they encourage the production of T-regulatory cells, which play a key role in keeping the immune system balanced and preventing unnecessary inflammatory responses. They are also associated with lower levels of pro-inflammatory signals and higher levels of anti-inflammatory ones. This is one of the reasons fibre intake is linked with lower levels of chronic inflammation, which is particularly important when managing autoimmune conditions such as rheumatoid arthritis.
4. It helps repair a leaky gut
Short-chain fatty acids (SCFAs) also help repair intestinal permeability, commonly known as leaky gut syndrome. A leaky gut triggers inflammation by allowing toxins and bacteria to enter the bloodstream.
Short-chain fatty acids, particularly butyrate, act as the "engineers" of your digestive tract. They repair a leaky gut by reinforcing three distinct layers of the intestinal barrier: the physical seals between cells, the protective mucus coating, and the underlying immune system.
Physical seals between the cells: The gut lining consists of a single layer of cells held together by proteins called tight junctions. In a "leaky" gut, these proteins break down, creating gaps that allow toxins to enter the bloodstream. SCFAs stimulate the production of these “zipper” proteins and provide energy needed by colon cells to fuel their constant growth and self-repair.
Protective mucus coating: A thick layer of mucus sits on top of your gut cells to physically block bacteria from ever touching the lining. SCFAs signal to specialised goblet cells to increase the production of mucus. Also, by thickening this layer, SCFAs create a better environment for beneficial bacteria to thrive, which then compete with and push out the harmful bacteria that cause leaks.
Underlying immune system: A leaky gut often triggers a "fire" of inflammation that further damages the lining. SCFAs stop this cycle. As mentioned above, SCFAs calm inflammation. They also trigger the release of antimicrobial peptides that act as natural antibiotics, killing off pathogens that would otherwise eat away at the gut barrier.
Here’s the flip side: when gut bacteria don’t have access to fibre, they turn to another easily accessible carbohydrate source, the intestinal mucus lining. Over time, they feast on this mucus and slowly but surely compromise the mucosal barrier, setting you up for leaky gut syndrome.
5. It prevents the growth of bad bacteria
SCFAs make the colon more acidic, preventing the growth of inflammatory and pathogenic bacteria such as Salmonella and E. coli, helping to correct dysbiosis and restore a healthy balance of bacteria in the gut.
What are the best high-fibre foods that produce SCFAs?
If you want to boost your SCFA production, these foods are your most effective tools:
Legumes: Lentils, black beans, chickpeas, and split peas are fibre heavyweights.
Whole Grains and Seeds: Oats, barley, chia seeds, and flax seeds.
Prebiotic Vegetables: Garlic, onions, leeks, and asparagus.
Resistant Starch: Found in green bananas or rice and potatoes that have been cooked and then completely cooled.
High-Pectin Fruits: Apples, pears, and avocados.
A note on transitioning
If your microbiome is not currently in a peak state, perhaps due to a recent course of antibiotics or a long period of low fibre intake, you should start slowly. Introducing too much fibre too quickly can cause temporary digestive distress if you do not yet have the bacterial population to handle the workload. There are specific protocols for gradually reintroducing these foods to rebuild your colony comfortably.
Conclusion
A helpful general goal is to aim for around 30 different plant varieties per week. Dietary diversity supports microbial diversity, which in turn helps ensure a steady production of beneficial compounds like SCFAs. The good news is that herbs, spices, nuts, seeds, and even your morning coffee all count towards that target, so it’s more achievable than it sounds.
As a Nutritionist and Health Coach, I work with clients to build practical, personalised plans that support gut health and long-term well-being. You are not just feeding yourself. You are feeding trillions of tiny co-workers who have a big say in how you feel!
Comments