Consuming more fiber may help improve life expectancy for diabetics according to two recent studies from researchers at the University of Otago in New Zealand.
 
Type 2 diabetes has reached epidemic proportions worldwide, is associated with serious medical complications, and increases the risk of dying from COVID-19.
 
The two recent studies have shown eating more dietary fiber improves life expectancy, although food processing may remove these benefits.
 
One study, a review published in Plos Medicine, used data collected from 8,300 adults with type 1 or type 2 diabetes to show that those with a higher fiber intake faced a significant reduction in premature mortality compared to those eating the least fiber.
 
Lead author Dr. Andrew Reynolds, National Heart Foundation Fellow of the Department of Medicine, said compared with the New Zealand average of 19 grams of fiber per day, those consuming 35 grams per day have a 35% reduced risk of dying early.
 
His advice to increase fiber intakes by eating more whole grains, legumes, vegetables, and whole fruit applies to people across the globe, Reynolds said.
 
The research team also analyzed 42 trials with 1,789 participants where adults with prediabetes, type 1 or type 2 diabetes were given more fiber and whole grains for at least six weeks.
 
They found consistent improvements in blood glucose control, cholesterol levels and reductions in body weight when adults with prediabetes, type 1 or type 2 diabetes increased their fiber or whole grain intake.
 
Senior author Professor Jim Mann, from the Department of Medicine and Director of the Healthier Lives National Science Challenge, has been involved in diabetes research for over 40 years and led the first controlled trials of high fiber diets in diabetes in the 1970s.
 
“When our controlled studies confirmed the benefits of dietary fiber four decades ago, we never suspected that they would be quite so impressive,” he said. “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.”
 
In the second study, researchers found not all foods that contain fiber are created equal; while whole grains are an important source of fiber, their benefits may be diluted when heavily processed.
 
For this study, to be published in Diabetes Care, Reynolds and Mann led a trial in adults with type 2 diabetes living in Dunedin to consider the effects of food processing on the health benefits of whole grains.
 
Participants ate minimally-processed whole grain foods such as whole grain oats and chunky grainy bread for one fortnight, then more processed whole grain foods such as instant oats and whole meal bread for another fortnight.
 
“Whole grain foods are now widely perceived to be beneficial, but increasingly products available on the supermarket shelves are ultra-processed,” said Mann.
 
Researchers used cutting edge glucose monitors to record participant blood glucose levels over the day and night 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 participants consumed the minimally processed whole grains.
 
The results were most striking after breakfast, as that was when most of the whole grains were consumed. Researchers also observed something unexpected. Although participants were asked not to lose weight by eating less during the trial, results showed their average weight increased slightly after two weeks of eating processed whole grains, and decreased slightly after eating minimally processed whole grains.
 
These two studies, along with previous research, confirm choosing high fiber foods like whole grains, whole fruit, dark leafy greens or legumes is good for everyone, and important in managing diseases such as type 1 or type 2 diabetes, said Reynolds.
 
“However, we are now beginning to understand that how foods are processed is also important, and for whole grains when you finely mill them you can remove their benefits,” he concluded.