Quality not quantity: Study links minimally processed, high-fibre diets with reduced mortality
A series of systematic reviews and meta-analyses conducted by researchers in New Zealand have linked the high consumption of fibre – from wholegrains, whole fruits, vegetables and pulses – with a reduction in non-communicable disease.
According to the study, published in The Lancet, relevant clinical trials and cohort studies conducted over the past 40 years indicate that the incident of certain diseases, and deaths from those diseases, were reduced when participants increased their fibre and wholegrain consumption.
“We looked at total mortality as well as at cancer mortality, cardiovascular disease mortality, as well as at coronary heart, and stroke mortality,” lead author Andrew Reynolds told FoodNavigator.
“For incidents, we [also looked at] type 2 diabetes and a number of cancers, including breast, colorectal, prostate, endometrial, and oesophageal. All of these diseases are non-communicable – the main killers at the moment in the world,” he added.
The study also indicated a reduction in participants’ body weight and total cholesterol, which the University of Otago researcher said is a “nice complement, because our body weight and total cholesterol are big disposing factors for those sorts of diseases we looked at in the cohorts.”
A focus on quality
Dietary fibre is attracting increased attention from researchers of late, whether through suggested links between low dietary fibre intake and depressive symptoms, or fibre’s potential influence on the microbiome.
However, according to Reynolds, most people do not consume enough fibre in their day-to-day life. “Typically, at least half of the people in the world have less than 20 g of fibre a day.”
“The evidence from our paper suggests that most of the benefits really kick in from 25 g – 29 g of fibre, with more benefits beyond that,” he added.
Reasons behind the inadequate consumption of fibre may vary, Reynolds explained. “There are cultural norms, wherein white rice or really refined flour might be highly prized for different reasons,” he explained.
The message about the importance of fibre is also “boring” or dated, he continued. “It’s not new, there’s not an app to go with it…it’s a funny message to sell.
“We all know that fibre is good for us, and what we’re trying to do is to reintroduce that into the discussion [with a focus on] how many things it actually improves.”
Fibre, which is found in carbohydrates, may also have been ignored in intentionally low-carbohydrate diets, such as the ketogenic (keto) diet which is high-fat, moderate-protein and low-carbohydrate.
The study authors, however, are more concerned with the quality, rather than quantity, of carbohydrates. “It is too simplistic to only talk about low carbohydrate or high carbohydrate, when it is the quality of the carbohydrate that is really important.”
“A low carb diet could be full of fibre, but it could also be a high sugar, low-carb diet, where the only carbohydrate you’re having is sugar – so the body would respond differently to those.”
Food industry collaboration
So what role do food manufacturers have in all this? As “fundamental players” in what people eat, Reynolds urged food manufacturers to work closely with “those working in evidence-based health”.
“This work will need to look at the preservation of intact grains and fibres into foods that have a long shelf life and are palatable without the addition of added sugars, saturated fats, and sodium,” he said.
The study, which was commissioned by the World Health Organization (WHO), will be used to inform the organisation’s carbohydrate recommendations. The dietary guidelines are due to be released in the coming year.
Source: The Lancet
Published online: 10 January 2019
‘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