LONDON (REUTERS) - People who eat lots of high-fibre and whole grain foods have lower risk of heart disease, stroke, diabetes and other chronic diseases than people whose diets are low in fibre, a study commissioned by the World Health Organisation (WHO) says.

For every 8g increase in fibre eaten a day, total deaths and incidences of heart disease, type 2 diabetes and bowel cancer fell by 5 to 27 per cent, the study said. Protection against stroke and breast cancer also rose.

A good target for those wanting to reap health gains would be to eat 25g to 29g of dietary fibre a day, the analysis found.

The data, published in a series of systematic reviews and meta-analyses in The Lancet medical journal, also suggested higher dietary fibre intakes could give even greater protection.

"Our findings provide convincing evidence for nutrition guidelines to focus on increasing dietary fibre and on replacing refined grains with whole grains. This reduces incidence risk and mortality from a broad range of important diseases," said Professor Jim Mann of the University of Otago, New Zealand, who co-led the research.

According to the study, most people worldwide currently consume less than 20g of dietary fibre a day.

In Britain in 2015, an advisory committee on nutrition recommended an increase in dietary fibre intake to 30g a day, but only 9 per cent of British adults manage to reach this target. In the United States, fibre intake among adults averages 15g a day.

Prof Mann said the health benefits of dietary fibre - contained in foods such as whole grains, pulses, vegetables and fruit - come from its chemistry, physical properties, physiology and its effects on metabolism.

"Fibre-rich whole foods that require chewing and retain much of their structure in the gut increase satiety and help weight control," he said. "(And) the breakdown of fibre in the large bowel by the resident bacteria has additional wide-ranging effects including protection from colorectal cancer."