The Uncomfortable Truth About Fibre (And Why It Matters More Than Ever)

There’s a statistic that should make all of us pause.

Colorectal cancer, once considered a condition of older adults, is increasingly being diagnosed in younger people. Researchers are still working out exactly why, but one factor keeps coming up in the literature: we are not eating enough fibre. Not even close.

And most of us have no idea.

From “roughage” to research

For most of the 20th century, fibre was dismissed as waste, the part of food your body couldn’t use. It wasn’t until the 1980s that medical doctors Dennis Burkitt and Hugh Trowell began making the case that too little fibre in modern diets was causing serious harm, including constipation, gut dysfunction, and colon cancer.

Decades later, the data has caught up with them. And the picture isn’t pretty.

The intake gap is bigger than you think

Most dietary guidelines recommend 25 to 30 grams of fibre per day. Australians are currently averaging around 21 grams. Americans fare even worse, sitting at 10 to 15 grams on average.

Now compare that to contemporary hunter-gatherer populations, who regularly consume around 75 grams per day.

That’s not a small shortfall. That’s a fundamentally different relationship with food.

What fibre actually does

Fibre is made up of carbohydrates your small intestine cannot digest. They pass through intact and arrive in your large bowel, where your gut microbiome goes to work fermenting them into short-chain fatty acids.

One of these, butyric acid, is particularly important. It acts as the primary fuel source for the cells lining your large bowel, and research suggests it actively inhibits those cells from developing into polyps or cancerous lesions. Another class of short-chain fatty acids improves insulin sensitivity, helping to regulate blood glucose and reduce the risk of type 2 diabetes.

This is not abstract science. This is your gut, doing its job, if you give it what it needs.

The low-carb question

A common concern I hear from clients is whether they can get enough fibre on a lower carbohydrate diet. It is genuinely more difficult, because many of the richest fibre sources, whole grains, legumes, and fruit, also come with carbohydrates attached.

That said, it is not impossible. Vegetables like broccoli, cabbage, and most salad greens offer meaningful fibre without a significant carbohydrate load. The key is volume and variety, and that requires being deliberate about it.

Which brings me to the bigger point.

Most people are guessing

The honest truth is that most people have no real idea how much fibre they are consuming day to day. They assume they are doing reasonably well because they eat vegetables, or have oats for breakfast, or avoid processed food. But assumptions are not data.

Tracking your food intake, even for a short period, is one of the most eye-opening things you can do. Not to obsess over numbers, but to get an accurate picture of where you actually sit. For many people, a simple food diary reveals patterns they had no idea were there.

If you have been curious about what your diet actually looks like under the microscope, that is exactly the kind of thing we explore together in coaching.

Is coaching right for me? Find out here.