Taking the roughage road to health and vitality

While we obsess about ultra-processed foods with too much salt, sugar, fat, and additives, the often-forgotten yet crucial deficit in modern diets is their lack of fibre.

Fibre not only helps us to stay regular but evidence is mounting about how it is critical for a healthy gut microbiome. 

Study after study shows the role fibre plays in strengthening the immune system, supporting gut health, and reducing inflammation that forms the building blocks for chronic diseases such as heart disease, high blood pressure, obesity, type 2 diabetes and several cancers, including colon and breast cancer.

The human diet has been subject to vast changes over the last few hundred years. The gap formed by reduced fibre consumption is filled by the consumption of energy-dense, high-fat, high-sugar, high-salt foods, the staple of the Western diet.

Our ancestors are thought to have consumed 100g of fibre a day. Now, people from non-industrialised nations generally ingest up to 50g a day, while those from industrialised Western nations consume only 12–18g daily.

While different industrialised countries tend to have a similar gut microbiome pattern, a study in Natural Cellular Biology (2014) revealed how the gut microbiome of vegans and vegetarians more closely resembled that of non-industrialised countries with a high dietary fibre intake.

Current recommendations for dietary fibre intake, summarised in a paper in Nutrition Research Reviews (2017), lie between 30 and 35g per day for males and 25 and 32g per day for females.

Western societies are still not near these guidelines, and low fibre consumption remains a major public health issue. Even today’s recommended daily fibre intake is much lower than that consumed by our ancestors.

A paper in Medicine and Microbiology (2022) outlines the role of dietary fibre as a prebiotic, meaning it feeds the microbiota or ‘good’ bacteria in the large intestine, allowing it to flourish. 

This strengthens the immune system by preventing an overgrowth of the wrong bacteria in your gut.

When the gut bacteria consume fibre in the large intestine, they release acids that keep the colon healthy, such as short-chain fatty acid, butyric acid, acetic acid, and propionic acid.

A member of the Stanford University Lifestyle Medicine programme, Jessica Hope, explains how this works. “Microbiota in our gut need to eat just like we do, and when we eat, we are also feeding them. If we don’t feed them enough fibre, they will look around to see what else they can eat,” she says.

A study in Nature (2022) points towards the possibility that ‘leaky gut’ occurs when microbiota are so starved they begin to eat the lining of our intestine. This can lead to bacteria and toxins entering the bloodstream resulting in symptoms such as diarrhoea, bloating, and fatigue.

If there were ever a good reason to eat more fibre, that seems like a good one to me.

Evidence supports a strong link between fibre consumption and longevity. A paper in the Journal of Translational Medicine (2022) showed that for those who consume between the recommended 20 to 30g of fibre daily, there is a 10 to 20% reduction in death from any cause.

Easy ways to add fibre to your diet

Fibre is found in most minimally processed plant-based foods, including beans, whole grains, nuts, seeds, fruit, and vegetables.

Easy fibre-rich meals include:

• Breakfast — berries with wholegrain cereal or oatmeal;
• Lunch — leafy green salad with beans or lentils and avocado;
• Snack — popcorn, whole fruit (eat the skin if possible), nuts (almonds, walnuts);
• Dinner — brown rice, sweet potatoes, broccoli, carrots, brussels sprouts;
• Dessert — rhubarb or apple pie.

The microbiome comprises different kinds of bacteria that eat different high-fibre foods. For example, some bacteria digest black beans, other bacteria digest oats, while other bacteria digest cabbage or kale.

“To prevent gas and bloating, the keys are to drink lots of water and start slow when incorporating more fibre into your diet. The amount of fibre we eat should be just slightly more than the bacteria we already have in our guts are asking for,” Hope explains.

Rather than avoiding particular foods, incorporate them slowly into your diet, “allowing time for that specific bacteria to multiply”.

The research is very clear. If we all increased our fibre intake by as much as 10g per day, the reduction in all-cause mortality would be significant, and everyone would be a little bit healthier.

Adding berries to breakfast, beans to lunch, and a mix of vegetables and baked potatoes, as well as brown rice or pasta to dinner, could be a lifetime habit that makes all the difference.

• Dr Catherine Conlon is a public health doctor and former director of human health and nutrition, safefood