Trying to improve your blood sugar by eating more fiber? A new study shows that one healthy swap — switching to a high-fiber oat bread — may not be enough on its own.
Researchers across Germany, Norway and Sweden followed nearly 200 adults at risk of developing type 2 diabetes. For 16 weeks, participants replaced their regular bread with either a fiber-rich oat bread or a whole-grain wheat bread, eating at least three slices a day, six days a week.
The oat bread was enriched with a type of soluble fiber called beta-glucan, found naturally in oats. This fiber has been shown in earlier lab studies to lower blood sugar and cholesterol after meals. But those studies were done under controlled conditions, with carefully timed and measured meals.
In this real-world study, people ate the bread as they normally would at home — with different meals, at different times and alongside other foods.
The result? No meaningful improvements in blood sugar, insulin, cholesterol or other health markers were seen, despite the bread meeting European health standards for beta-glucan content.
“We designed a high-fiber ß-glucan enriched oat bread specifically for this study, aiming to test whether a simple dietary swap could yield measurable health benefits in everyday life,” said lead researcher Dr. Therese Hjorth. “However, our findings suggest that changing just one food item — even one with proven short-term benefits — is not enough to improve long-term glycemic control.”
Other researchers agree: relying on one “superfood” isn’t a magic bullet.
“Our study underscores the importance of a whole-diet approach rather than relying on single-food substitutions,” said Professor Jutta Dierkes, a co-author on the study.
And while high-fiber foods like oat bread can be helpful, they work best as part of broader eating habits.
“Functional foods like β-glucan-enriched bread can assist in consuming a healthy diet,” said Professor Anette Buyken, “yet broader dietary changes as well as environments facilitating healthy choices are needed to achieve meaningful health outcomes.”
The study was published in Clinical Nutrition and led by researchers from the University of Bergen, Chalmers University of Technology, Nofima and other institutions. It was funded by national research councils in Norway, Sweden and Germany through a European health initiative called A Healthy Diet for a Healthy Life.