People who consume plenty of fibre and whole grains have a reduced risk of developing chronic diseases, such as cardiovascular disease and cancer, a new study has found.
The study was commissioned by the World Health Organization (WHO) in order to help inform the development of new recommendations for optimal daily fibre intake when it comes to providing protection against non-communicable diseases.
Non-communicable diseases, also known as chronic diseases, tend to be of long durations and occur as a result of a combination of genetic, physiological, environmental and behavioural factors. They include cancer, heart disease, diabetes and respiratory diseases, such as asthma.
According to the WHO, chronic diseases kill 41 million people every year - which is 71% of all deaths globally.
As part of this study, researchers analysed 185 observational studies involving 135 million people, and 58 clinical trials involving 4,635 adults. These studies involved initially healthy participants, so the findings cannot be applied to those with existing chronic diseases.
The researchers found that for every 8g increase of dietary fibre consumed each day, there was a 5-27% decrease in the incidence and total deaths from coronary heart disease, type 2 diabetes and colorectal cancer.
Protection against stroke and breast cancer also increased.
While the consumption of 25-29g of fibre per day was adequate, the findings suggest that a higher daily intake could offer even greater protection.
When it came to whole grains, the researchers found that for every 15g increase consumed per day, there was a 2-19% decrease in the incidence and total deaths from coronary heart disease, type 2 diabetes and colorectal cancer.
A higher intake of whole grains was linked with an overall reduction in chronic disease risk of 13-33% - which is equivalent to 26 fewer deaths per 1,000 people.
"The health benefits of fibre are supported by over 100 years of research into its chemistry, physical properties, physiology and 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 and can favourably influence lipid and glucose levels.
"The breakdown of fibre in the large bowel by the resident bacteria has additional wide-ranging effects including protection from colorectal cancer," explained one of the study authors, Prof Jim Mann, of the University of Otago in New Zealand.
He insisted that these 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," he said.
The researchers added that while their study did not find any risks associated with dietary fibre, a high intake could negatively impact people with low iron or mineral levels, as high levels of whole grains can further reduce levels of iron.
They also noted that their study looked mainly at foods rich in naturally occurring fibre, rather than synthetic fibre, such as powders, that can be added to foods.
Foods rich in fibre include fruits, such as raspberries, bananas and apples (with skin on), and vegetables such as broccoli, turnip and sweetcorn. Other fibre-rich foods include brown rice, wholemeal bread, bran flakes, quinoa, lentils, baked beans, almonds and pistachios.
Whole grain foods refer to any foods made from cereal grains such as wheat, rice, oats and barley. They include brown rice, whole grain bread, popcorn, whole wheat cereals, whole wheat pasta and whole wheat crackers.
Details of these findings are published in the journal, The Lancet.