Is dietary fibre the key to a longer life?

Wednesday, 27 May 2020

Recent studies from University of Otago have shown that eating more dietary fibre improves life expectancy.

About the research

One study using data collected from 8300 adults with type 1 or type 2 diabetes found those with a higher fibre intake had a significant reduction in premature mortality compared to those eating lower levels of fibre.

Dr Andrew Reynolds says people consuming 35g of fibre per day have 35% less risk of dying early compared with people who eat 19 grams of fibre per day.

His advice is to increase fibre intakes by eating more wholegrains, legumes, vegetables, and whole fruit.

New ways to add fibre

“Try a few different ways to increase your fibre intake, and see what works best for you,” Dr Reynolds said.

“If you eat white bread or rolls, try changing to wholegrain. Try brown rice, brown pasta, or add half a tin of legumes to meals.

“Try an extra vegetable with your main meal – fresh, frozen, or canned are all good choices.”

The health benefits of fibre

The research team also analysed 42 trials with 1789 participants where adults with prediabetes, type 1 or type 2 diabetes were given more fibre and wholegrains for at least six weeks.

They found consistent improvements in blood glucose control, cholesterol levels and reductions in body weight when participants increased their fibre intake.

Professor Jim Mann who has been involved in diabetes research for over 40 years said “When our controlled studies confirmed the benefits of dietary fibre four decades ago, we never suspected that they would be quite so impressive,” he says.

“It has taken 40 years of research and these meta analyses to be able to show that this dietary treatment can have an effect as striking as that produced by medications.”

Not all fibre is created equal

In the second study, researchers found not all foods that contain fibre are created equal.

While wholegrains are an important source of fibre, their benefits may be diluted when heavily processed.

In this study, Dr Reynolds and Prof. Mann led a trial in adults with type 2 diabetes to consider the effects of food processing on the health benefits of wholegrains.

Participants ate minimally processed foods for one fortnight, then more processed foods  for another fortnight.

“Wholegrain foods are widely perceived to be beneficial, but many products available on the supermarket shelves are ultra-processed,” says Prof. Mann.

Researchers used cutting edge glucose monitors to record participant blood glucose levels during the two-week intervention periods.

Results showed improved blood glucose levels after meals and reduced variability of blood glucose levels throughout the day when they consumed the minimally processed wholegrains.

The results were most striking after breakfast, as that was when most of the wholegrains were consumed.

Something unexpected

Participants were asked not to lose weight by eating less during the trial. Results showed their average weight increased after two weeks of eating processed wholegrains and decreased after eating minimally processed wholegrains.

These two studies, along with previous research, confirm high fibre foods are important in managing conditions like diabetes.

“We are now beginning to understand that how foods are processed is important. For wholegrains when you finely mill them you can remove their benefits,” he concluded.

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