The vital role of fibre in gut health

Social media influencers are championing fibre as the latest wellness essential, sharing tips on adding more to your diet.  

But this focus on fibre is more than a trend. In fact, it is well-founded. Dr Melvyn Letier, a gastroenterologist at Mediclinic Constantiaberg, explains that adequate fibre intake can help prevent colorectal cancer, one of the most common cancers, while supporting overall gut health.

Your gut ecosystem

Your gut contains both beneficial bacteria, harmful pathogens, and everything in between. “This complex ecosystem, known as your gut microbiome, plays a crucial role in digestion, immune function, and even mood regulation,” says Dr Letier. “When this delicate balance tips toward harmful bacteria, inflammation increases, potentially setting the stage for various health problems. These can include colon cancer and inflammatory bowel disease (IBD) such as Crohn’s disease and ulcerative colitis.

Your gut microbiome's health directly reflects what you eat. When you provide the right nutrients, it functions well – and fibre plays a crucial role in this process.

Two main types of fibre

1. Soluble fibre dissolves in water to form a gel-like substance, helping to lower cholesterol and regulate blood sugar. You'll find it in oats, beans, apples, and citrus fruits.
2. Insoluble fibre doesn’t dissolve in water but adds bulk to stool and helps food pass more quickly through the stomach and intestines. Whole grains, nuts, vegetables, and wheat bran are excellent sources.

How fibre works in your body

Fibre is the part of plant foods that your body can't digest. It travels through your system mostly unchanged until it reaches your large intestine, where it becomes food for the good bacteria living there. When these bacteria break down the fibre, they create beneficial compounds called acetate, propionate and butyrate (SCFAs).

“These compounds are good fuel for your colon cells, keeping them healthy and functioning well,” Dr Letier says. SCFAs can also help strengthen your intestinal lining, reducing inflammation.

“A fibre-rich diet can also help you maintain a healthy weight, control blood sugar levels, lower cholesterol, and reduce the risk of heart disease Plus, it promotes regular bowel movements and can alleviate digestive issues like constipation and bloating.”

The colon cancer connection

Research shows that eating more fibre is linked to a lower risk of colorectal cancer. “Fibre helps speed up the time it takes for waste to pass through your colon, reducing the time potential carcinogens spend in contact with your intestinal walls,” explains Dr Letier.  

A fibre-rich diet also promotes a diverse, healthy gut microbiome that can fight harmful bacteria and reduce chronic inflammation. “Eating enough fibre changes your gut for the better. It feeds the good bacteria in your intestines while starving the bad bacteria that can cause problems.” 

When good bacteria are well-fed, they create an environment that makes it hard for cancer to develop. The fibre also makes your gut more acidic, which helps trap and remove dangerous chemicals that could cause cancer.

Add more fibre to your diet

Small dietary changes can significantly improve your gut health. Here’s how to get started:

• Start slowly. Too much fibre can cause bloating so gradually increase your intake to avoid digestive discomfort. Add 5g weekly until you reach the recommended daily amount of 25-35g.
• Eat a variety of colourful foods. Include different fruits and vegetables, whole grains, legumes, nuts, and seeds in your meals. Each type of fibre feeds different beneficial bacteria in your gut.
• Drink plenty of water. Fibre needs adequate water to work effectively, so keep a water bottle handy throughout the day.
• Add fermented foods to your diet. Products like yoghurt, amasi, buttermilk, kefir, sauerkraut, and kimchi introduce helpful bacteria directly into your digestive system.
• Limit processed foods. They usually lack fibre and can disrupt your gut microbiome balance.

“While genetics play a role in colon cancer risk, lifestyle factors, particularly diet, are largely within your control,” says Dr Letier. “Eating plenty of fibre-rich foods doesn’t just help prevent cancer; it builds a foundation for overall wellness.”