Dietary fiber — a category of carbohydrates that aren’t easily broken down by the digestive system — has long been touted for various health benefits, from promoting bowel regularity to reducing your risk of heart disease.
But the role of fiber in diabetes, particularly its effect on blood glucose control, has been a source of interest for many researchers. A number of studies over the years have found a connection between intake of certain types of fiber and blood glucose levels, but the variety of fiber types and doses in these studies have made it difficult to draw strong conclusions or recommendations.
New overview of studies on fiber
To overcome the limitations of any one study on fiber supplements and blood glucose control, a research team based at the University of Toronto in Canada analyzed data from 28 different studies that lasted at least 3 weeks and looked at outcomes in people with Type 2 diabetes.
In each study, participants took a supplement containing a form of soluble fiber called viscous fiber. This type of fiber forms a gel when it dissolves in water, and it’s widely found in both food and certain fiber supplements.
Published in January 2019 in the journal Diabetes Care, the researchers’ analysis found that at the median (middle of the group) dose among the 28 studies — about 13 grams per day of viscous fiber — participants saw an average reduction in HbA1c (a measure of long-term blood glucose control) of 0.58 percent.
This HbA1c reduction, the researchers note, is greater than the 0.3 percent threshold the U.S. Food and Drug Administration (FDA) looks for when evaluating new diabetes drugs. The researchers also found improvements in fasting blood glucose and insulin sensitivity from taking the median fiber dose.
Should you take a fiber supplement?
Based on the results of the latest analysis, there’s a clear benefit from taking a viscous fiber supplement on blood glucose control in people with Type 2 diabetes.
Each study included in the analysis looked at the effects of taking the fiber supplement in addition to any diabetes medications the participants were already taking. Thus all measured outcomes were in comparison with not taking fiber, rather than with fiber stacked up against an alternative treatment.
So it’s unknown whether fiber might be a good alternative to certain diabetes drugs or other treatment recommendations, such as following an exercise program or making dietary changes.
It’s also unknown whether you could get a similar — or even greater — benefit from including foods containing viscous fiber in your diet, compared with taking a supplement. Participants weren’t told to modify their diets in any of the included studies.
Because it can be tested as an isolated intervention at a measured dose, a fiber supplement is much easier to study than dietary changes that result in a certain fiber intake. But it’s conceivable that dietary changes could lead to even more drastic blood glucose improvements, since they could reduce intake of easily digested carbohydrate while increasing fiber intake.
So if you want to do something simple that could improve your blood glucose control, a viscous fiber supplement may be worth considering. But talk to your doctor about the role of fiber in your diet more generally, and about how various dietary changes might be good for your diabetes.