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When it comes to our diet, there is an ever-changing list of things touted as the key to better health: cutting out carbs, eating like a caveman or dosing up on supposed superfoods such as turmeric. Most fail to live up to the hype 鈥� but there is one supernutrient that bucks this trend.

It is common knowledge that dietary fibre is good for you, but few of us appreciate just how far-reaching its health benefits go. Being in the know is worth your while, though, especially given that the diets common in high-income nations mean it is all too easy to miss out.

Many of us will have experienced first hand the effects of dietary fibre on our body. Sometimes dubbed 鈥渘ature鈥檚 laxative鈥�, a lack of it can cause constipation. But there is much more to fibre than bowel movements. Diets high in this constituent are associated with reduced risks of many health conditions, including cancers and heart disease. This is because fibre isn鈥檛 just cardboardy filler, it is also food for the microorganisms in our gut. That means its effects can be felt throughout your body, as this microbiome influences the health of our immune system, brain and more, via the chemicals it produces.

鈥淔ibre is the part of our diet that we cannot digest. Most comes from plant cell walls,鈥� says at the University of Aberdeen in the UK. Chemically, it is made up of long-chain carbohydrates. There are many types, the properties of which vary, including how soluble they are. They include resistant starch, found in unripened bananas and oatmeal, and cellulose, typically found in whole grains.

Evidence for high-fibre diet

Dietary fibre was largely ignored until around 50 years ago. In 1969, surgeon Denis Burkitt began arguing that several bowel diseases, including colorectal cancer, were . Decades later, supporting fibre鈥檚 benefits .

鈥淭he evidence for dietary fibre is now overwhelming,鈥� says at Otago University in Dunedin, New Zealand. He co-authored a covering 185 studies that tracked 58 clinical trials. This found that people who ate the most fibre had a 15 to 30 per cent lower risk of all-cause and cardiovascular-related death over the study periods, compared with those who ate the least. They also had lower incidences of colorectal cancer, stroke, coronary heart disease and type 2 diabetes.

What鈥檚 more, the health benefits rose in line with dietary fibre consumption. That is suggestive of a causal relationship, and a number of randomised controlled trials, the gold standard for medical evidence, show that high-fibre diets lead to lower blood pressure and cholesterol levels. A lack of dietary fibre is estimated to cause more than half a million deaths globally.

When it comes to the gut microbiome鈥檚 part in this, we know that a community of microorganisms 鈥� particularly bacteria 鈥� feeds on fibre in the large intestine. Some bacteria can break down the long carbohydrate chains into smaller molecules that they and other microbes can digest. Others take those breakdown products and ferment them, producing short-chain fatty acids such as butyrate. 鈥淚t鈥檚 an ecosystem,鈥� says Louis.

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This benefits us in many ways. 鈥淭he large intestine prefers butyrate as an energy source over other molecules,鈥� says Louis, so the microbes that produce it are indirectly nourishing our gut wall. This may help explain why fibre reduces the risk of colorectal cancer. There are also in many parts of our bodies, which influence our nervous and immune systems.

But it isn鈥檛 all about the microbiome. Fibre also leads to us feeling less hungry by stimulating the release of an appetite-reducing hormone called PYY in the small intestine, plus it slows the absorption of glucose into the blood.

How much fibre should you eat?

With this in mind, how much fibre should you eat, and what kind? The World 91色情片 Organization ; in the UK, . This is equivalent to the fibre content of 12 to 14 slices of wholewheat bread.

Most of us fall woefully short of this. A 2024 study of more than 2000 adults in Switzerland found that of 30 g per day, with less fibre consumed by those with the highest intake of ultra-processed food. In the UK, on average , but the situation seems to be worse in the US, where a 2017 study discovered that only around met recommended guidelines. This deficit may be , as it is .

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One way to boost intake is to eat foods that have been supplemented with extracted fibre or synthetic fibre made from ingredients of plant origin. However, unlike for whole foods, 鈥渢here is no substantiated clinical epidemiological evidence鈥� for health benefits from these forms of fibre, says Mann. 鈥淚 do not feel that degree of comfort to tell people that they can have extracted or synthetic fibre.鈥� The good evidence is for diets where the fibre comes from naturally fibrous foods.

There is also emerging evidence that different kinds of fibre have differing effects. A found that insoluble fibre seemed to be more effective than the soluble form at reducing the risk of death from cancer and cardiovascular disease. It also found that fibre from whole grains, cereals and vegetables was associated with lower all-cause mortality, while that from nuts and seeds specifically reduced the risk of death from cardiovascular disease. Similarly, Mann says fibre from legumes seems to have the strongest effect on blood glucose levels, while cereal fibre tends to mostly affect the bowel.

So, as ever with food, variety is good. 鈥淓at lots of plant-based foods, especially vegetables and fruits, wholegrain cereals, pulses 鈥� peas and beans 鈥� and nuts,鈥� says at Newcastle University in the UK, 鈥渁ll of which are good sources of dietary fibre.鈥�