A high-fibre diet can reduce the chances of premature death by up to 30%, according to a landmark review commissioned by the World Health Organization.
Eating more fibre, such as wholegrains, legumes, fruit and vegetables, also reduces the chances of heart disease, stroke, colorectal cancer and type 2 diabetes.
Speaking to BBC News, Professor John Cummings, one of the authors, said: “The evidence is now overwhelming, and this is a game-changer that people have to start doing something about.”
Stats and facts – what you need to know
The review suggests that if 1,000 people switched from a low-fibre diet (less than 15g) to a high-fibre diet (between 25 and 29g), 13 deaths and six cases of heart disease would be prevented.
This is over the course of 185 studies and 58 clinical trials, which followed people for approximately one to two decades. The review was published in the Lancet medical journal.
The analysis found a 15-30% reduction in deaths from all causes, a 16-24% reduction in cases of coronary heart disease, stroke, type 2 diabetes and colorectal cancer.
Professor Jim Mann, whose research into dietary sugar resulted in sugar taxes around the world, led the study at the University of Otago in New Zealand.
He said: “We have got very strong evidence that a high-fibre diet […] has an enormous protective effect.
“A wide range of diseases including diabetes, cardiovascular disease and cancer benefit from a high-carbohydrate diet.”
Professor Cummings added: “We need to get this written in stone and part of people’s lives.”
Blow to low carb diets
The recent backlash against sugar has resulted in several diets which limit carbohydrates – including the fibrous variety that can save lives and prevent disease.
According to Professor Mann, consuming high levels of fibre is very difficult on a low-carb diet, adding that it’s “pretty well impossible” to get enough fibre from fruit and vegetables alone.
Professor Nita Forouhi, from the University of Cambridge, said: “We need to take serious note of this study.
“Its findings do imply that, though increasingly popular in the community at large, any dietary regimes that recommend very low carbohydrate diets should consider the opportunity cost of missing out on fibre from wholegrains.
“This research confirms that fibre and wholegrain intakes are clearly important for longer term health.”
Fibre and weight loss
Fibre is well-known for maintaining digestive health and helping us feel fuller for longer.
High-fibre foods take longer to chew, resulting in slower eating and giving the body more time to register a feeling of satiety.
Mann said: “Fibre-rich whole foods that require chewing and retain much of their structure in the gut increase satiety and help weight control – and can favourably influence lipid and glucose levels.”
The study showed a reduction in both body weight and cholesterol when switching to a high-fibre diet that includes wholegrains.
What is fibre?
Fibre refers to a group of substances in plant foods which cannot be completely broken down by human digestive enzymes.
It is found in edible plant foods such as cereals, fruits, vegetables, dried peas, nuts, lentils and grains.
Doctor Helena Popovic said: “Fibre is a prebiotic. It provides nutrients for the growth of healthy bacteria in your colon. And the healthier your bacteria, the more favourable enzymes they produce, so the better your biochemistry and digestive system will be.”
How much fibre should I eat?
The review stated that we should be eating at least 25g to 29g of fibre a day, an “adequate” amount for improving health. However, there are indications that consuming over 30g could bring further health benefits.
At present, just 9% of the UK population consumes the recommended amount of fibre per day. Most people around the world eat less than 20g a day.
Elaine Rush, a professor of nutrition at Auckland University of Technology, said: “It is not easy to increase fibre in the diet.”
Professor Cummings added that it could be a “big change” for some people and “quite a challenge”.
Here is what 25-30g of daily dietary fibre could look like, according to Professor Rush:
- Half a cup (170g) of rolled oats – 9g fibre
- Two Weetabix – 3g fibre
- A thick slice of brown bread – 2g fibre
- A cup (340g) of cooked lentils – 4g fibre
- A potato (cooked with the skin on) – 2g fibre
- Half a cup (170g) of chard – 1g fibre
- A carrot – 3g fibre
- An apple (with the skin on) – 4g fibre
How do you know if you’re not getting enough? According to Robbie Clark, an accredited practising dietitian and co-founder of The Health Clinic, the first symptom you might notice is constipation, along with cramping, pain and bloating.
He added: “Another is if your stools are quite pellet-like. If it’s hard to pass and you’re straining, that’s a sign of constipation as well. Essentially, fibre is really important for keeping our bowels regular.”