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Soluble fiber may improve diabetes control

(Reuters Health) – People with diabetes who take soluble fiber supplements have slightly lower blood sugar than diabetics who don’t add this type of fiber to their diets, a research review finds.

Researchers focused on supplements containing viscous fiber, a type of soluble fiber that forms a thick gel when mixed with water. Foods like legumes, asparagus, oats, and flax contain viscous fiber; supplements with this type of fiber include guar gum, psyllium and pectin.

To examine the connection between viscous fiber supplements and blood sugar, researchers examined data from 28 clinical trials with a total of 1,394 participants with diabetes. People were randomly chosen to take viscous fiber supplements or to use other types of supplements without viscous fiber or no supplements at all.

Among the people taking viscous fiber supplements, half consumed doses above 13 grams daily, for periods ranging from three weeks to a year. Compared to participants who didn’t take viscous fiber, those who did had better blood sugar control. They had lower levels of hemoglobin A1c, which reflects average blood sugar over about three months. They also had lower blood sugar levels on an empty stomach, known as fasting glucose levels.

These results “suggest that intake of around 1 tablespoon of concentrated viscous fibers such as konjac, guar, pectin or psyllium would result in reductions in A1c and other diabetes risk factors,” said senior study author Dr. Vladimir Vuksan of St. Michael’s Hospital and the University of Toronto in Canada.

People with diabetes have long been advised to consume more fiber as one way to help lower their blood sugar. But many, particularly those who follow a typical Western diet with lots of meat and potatoes, don’t get anywhere near enough fiber to make a meaningful difference in diabetes, the study authors note in Diabetes Care.

Supplements have become an increasingly common way for these patients to get more fiber. While the reason viscous fiber seems to lower blood sugar isn’t clear, scientists think that it might work in a variety of ways, including improving microbial health in the gut.

Most trials in the study focused on hemoglobin A1c levels. Readings above 6.5 percent signal diabetes. Fiber supplements were associated with average A1c reductions of 0.58 percent, which is greater than the minimum 0.3 percent reduction the U.S. Food and Drug Administration looks for in evaluating new diabetes drugs, the study authors note.

In addition to HbA1c, other markers of diabetes including fasting glucose and insulin sensitivity were also improved.

One limitation of the analysis is that some studies were too small and brief to draw broad conclusions about the long-term impact of fiber supplements on all patients with diabetes.

It’s also possible that so-called publication bias, or the disclosure of only positive trial results, may have made fiber supplements appear more effective than they really are, the study authors note.

“These results suggest that viscous fiber supplements could be considered in the management of type 2 diabetes,” said Nour Makarem, a researcher at Columbia University Irving Medical Center in New York City who wasn’t involved in the study.

“However, additional studies are needed to further examine the effects of different types of fiber on blood glucose regulation and to comprehensively study the health effects and the optimization of incorporating viscous fiber supplements into a healthful diet pattern,” Marakem said by email.

SOURCE: Diabetes Care, online January 7, 2019.

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