Brain bran: The protective effect that fibre has on cognition – BBC

Brain bran: The protective effect that fibre has on cognition

By Melissa Hogenboom, 26 January 2026

Eating fibre can improve health, lengthen lifespans, and even protect our brains. Yet many of us are still coming up short on this “essential nutrient”.

A diet high in whole grains, fruits, pulses, nuts and seeds – all of which are full of fibre – can have huge benefits for both our bodies and our brains.

Emerging research shows fibre supercharges the microbiome and influences the gut-brain axis, which is the communication channel that runs between the gut and the brain; slowing down symptoms of cognitive decline.

Increasing fibre intake is one of the most impactful dietary changes for cognitive health, says Karen Scott, professor of gut microbiology at the Rowett Institute, University of Aberdeen. Alternatively, a fibre deficit has been found to be a leading dietary risk factor for ill health.

Yet many of us aren’t eating enough. In the US, about 97% of men and 90% of women do not eat enough fibre. Most eat less than half the recommended daily amount. In the UK, over 90% of UK adults fall short, with many other countries showing similar deficiencies. 

So why exactly is fibre so beneficial, and how can we eat more of it?

Gut feeling: How fibre functions

Fibre is a carbohydrate that can’t be easily broken down by the digestive enzymes. Most therefore passes through the gut largely unchanged.

It increases the size of stools. It keeps us feeling fuller for longer and, as we digest it slowly, it leads to a more gradual rise in blood sugar levels. Those who eat more whole grains per day have been shown to have a lower BMI and less belly fat than those who eat refined grains.

A diet high in fibre can also help lengthen a lifespan and should therefore be considered an essential nutrient, says John Cummings, emeritus professor of experimental gastroenterology at the University of Dundee.

A review which Cummings co-authored found that those who ate the most fibre showed a 15-30% reduced risk of mortality compared to those who ate the least. Sufficient fibre consumption, which the researchers say is about 30g per day, lowers the risk of coronary heart disease, stroke, type 2 diabetes and colon cancer – and translates as 13 fewer deaths per 1,000 people.

The greatest benefits were seen at 25-29g of fibre per day. To achieve that, you could incorporate fibre into every meal and snack, with portions of fruits or vegetables in each meal. A skin-on jacket of potato with baked beans followed by an apple will provide about 15.7g of fibre for instance. Snacking on nuts and seeds will also increase your intake – a handful of nuts (about 30g) contains 3.8g of fibre.  

Key to this impact is fibre’s relationship to the gut microbiome. 

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As our gut bacteria digest fibre, beneficial byproducts are produced, including the short-chain fatty acids acetate, propionate and butyrate. It’s these metabolic products that provide critical energy for cells and are linked to significant reductions in mortality, explains Cummings. 

Minding your meals: How fibre protects the brain

A high-fibre diet is also now believed to be particularly important for brain health, explains Scott. The presence of the fatty-acid butyrate helps maintain the lining of the gut, she says, thus reducing the risk of harmful substances entering the bloodstream and affecting the brain.

Editor’s Note: Featured image at the top is WP AI. –DrWeb

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