The review draws on 40 years of observational studies and clinical trials to reveal a 15-30% decrease in all-cause and cardiovascular-related deaths when comparing higher fibre intake to the lowest.
Commissioned by the World Health Organization (WHO), the review also points to a 16-24% decrease in coronary heart disease, stroke, type 2 diabetes and colorectal cancer cases resulting from eating fibre-rich foods.
“Our findings provide convincing evidence for nutrition guidelines to focus on increasing dietary fibre and on replacing refined grains with whole grains,” said professor Jim Mann, study author based at the University of Otago, New Zealand.
“This reduces incidence risk and mortality from a broad range of important diseases.”
‘Added fibre’
The team, which include researchers from the University of Dundee in Scotland, point to the breakdown of fibre in the large bowel by the resident bacteria as key to fibre’s prebiotic effects.
“The principal function of the microbiome is digestion of fibre and other carbohydrates that escape breakdown in the small bowel, and it is the availability of fibre in the diet that dominates the metabolism of the gut microbiome and leads to protection from conditions such as colorectal cancer,” study said.
Recent research continues to show the health benefits associated with high fibre diets, with weight management, gut health and even mental health all high on the agenda for consumers.
Innova Market Insights revealed 33% of UK consumers have increased fibre consumption, with the majority citing digestive health.
The market research firm reported a 55% increase in fibre being added to sport nutrition products in the last five years.
Review details
Extracting data from 185 observational studies involving 4,635 healthy adult participants, the team focused on premature deaths from and incidence of coronary heart disease, cardiovascular disease and stroke, as well as incidence of type 2 diabetes and colorectal cancer.
Main findings attributed an eight gram (g) increase of dietary fibre per day with a 5-27% decrease in total deaths and incidences of coronary heart disease, type 2 diabetes and colorectal cancer.
Additionally protection against stroke, and breast cancer also increased as the researchers believed higher intakes of dietary fibre (more than 25-29g each day) could provide even greater protection.
“For every 15g increase of whole grains eaten per day, total deaths and incidences of coronary heart disease, type 2 diabetes and colorectal cancer decreased by 2-19%,” the study stated.
“Higher intakes of whole grains were associated with a 13-33% reduction in non-communicable disease (NCD) risk.”
The figures translated into 26 fewer deaths per 1,000 people from all-cause mortality and seven fewer cases of coronary heart disease per 1,000 people.
Remarking on the study’s findings, professor Gary Frost from Imperial College London, highlighted a number of considerations, commenting that total carbohydrate intake was not included in the systematic review and meta-analysis.
‘Caution advised’
“Second, although the absence of association between glycaemic index and load with non-communicable disease and risk factors is consistent with another recent systematic review, caution is needed when interpreting these data, as the number of studies is small and findings are heterogeneous,” he added.
“Third, the absence of quantifiable and objective biomarkers for assessing carbohydrate intake means dietary research relies on self-reported intake, which is prone to error and misreporting. Improving the accuracy of dietary assessment is a priority area for nutrition research.”
Professor Frost added that the analyses “Provided compelling evidence that dietary fibre and whole grain are major determinants of numerous health outcomes and should form part of public health policy”.
Current public health statistics are damning in populations and fibre intake particularly in industrialised nations with most people consuming less than 20 g of dietary fibre per day.
In 2015, the UK Scientific Advisory Committee on Nutrition recommended an increase in dietary fibre intake to 30 g per day, but only 9% of UK adults manage to reach this target. In the US, fibre intake among adults averages 15 g a day.
Naveed Sattar, professor of metabolic medicine at the University of Glasgow, said this was "an important paper which highlights better than before the potential value to health of higher dietary fibre intake".
"However, as with the vast majority of nutritional data, most of the evidence comes from observational studies and one has to be cautious about conclusions reached given the unavoidable biases they contain.
"That noted, this paper importantly also includes risk factor data from trials and the reductions in weight and other known causal risk factors such as blood pressure, cholesterol, etc seen with higher fibre (whole grain) diets, although modest do support the overall findings linking more fibre in the diet to less heart disease, diabetes, cancers, and potentially longer life.
"So I tend to believe the overall findings are directionally true and so concur with the authors conclusions when they write “recommendations to increase dietary fibre intake and to replace refined grains with whole grains is expected to benefit human health.”
Source: The Lancet
Published online: dx.doi.org/10.1016/
“Carbohydrate quality and human health: a series of systematic reviews and meta-analyses.”
Authors: Andrew Reynolds, Jim Mann, John Cummings, Nicola Winter, Evelyn Mete, Lisa Te Morenga.
