Study: Glycemic Index Education Leads To Better Diabetes Control

COLUMBUS, Ohio – Nine weeks of education about the glycemic index in foods is enough to encourage adults with type 2 diabetes to adopt better dietary habits that result in improvements to their health, recent research suggests.

Participants in a clinical trial attended weekly sessions to learn about the potential benefits of low-glycemic-index foods – carbohydrates that are digested slowly and are less likely to spike blood-sugar levels than are carbohydrates that have a high glycemic index.

After nine weeks, the participants had adopted a lower glycemic-index diet and recorded lower weight, smaller waists and improved blood sugar levels.

And when they were tested again another nine weeks later – during which they received no additional education – the participants had maintained most of those benefits.

The research addresses a controversy in the nutrition community, where some practitioners believe the principles behind maintaining a low-glycemic-index diet are too complicated for average consumers.

“We found that with education, people with diabetes were able to adopt a lower glycemic-index diet. And it had a significant improvement in their weight control and glucose control,” said Carla Miller, senior author of the study and an associate professor of human nutrition at Ohio State University.

“A vast majority of people with diabetes don’t get sufficient education about their condition when they are diagnosed. And yet for many patients, that’s the only time they receive nutrition education. What they really need is continued education and support to help them maintain good control.”

The research is published in a recent issue of the journal Public Health Nutrition.

In the study, people with diabetes were randomized into one of two groups. One group participated in the nine-week intervention immediately, and the other group waited for nine weeks before undergoing the same intervention.

After nine weeks of intervention, participants in the first group lost, on average, about 2.3 kilograms (5.1 pounds), decreased their waist circumference by 2.9 centimeters (1.1 inches), reduced their body mass index, a ratio of weight to height, by almost a point and lowered their blood glucose concentration after eating.

The 103 participants who completed the study were between the ages of 40 and 70 years, had been diagnosed with type 2 diabetes for at least one year, and did not require insulin therapy for diabetes management. For the most part, participants were already doing a good job of controlling their blood glucose levels.

Each group education session lasted between 90 minutes and two hours. Session topics included self-monitoring food intake and portion sizes, carbohydrate counting and maintaining behavioral change. Overall, the intervention emphasized selecting lower-glycemic-index foods instead of restricting overall carbohydrate intake.

The glycemic index is represented by a scale from 1 to 100. Foods that tend to slow the speed of digestion and prevent rapid increases in blood sugar include many vegetables, whole grains, dairy foods, nuts and seeds, beans and fruits. They are considered low-glycemic-index foods if they have an index of 55 or fewer points. Foods with a point value of 100 are the equivalent of pure glucose.

“The emphasis historically has been to control how much carbohydrate people with diabetes eat rather than the type of carbohydrate they choose. And the controversy has been that the glycemic index is so complicated, it’s just another thing that we are asking people to worry about,” Miller said. “And they do have to balance many different variables to get all of these blood parameters under control. That’s another reason they need a lot more education than they receive.”

Health measures and diet and physical activity information were collected before and after the intervention period. During the intervention, participants tested their blood glucose levels before and after meals four days per week. To track the participants’ food choices, researchers made periodic unannounced phone calls and asked patients to recall what they had eaten in the previous 24 hours.

After nine weeks of intervention, participants in the first group lost, on average, about 2.3 kilograms (5.1 pounds), decreased their waist circumference by 2.9 centimeters (1.1 inches), reduced their body mass index, a ratio of weight to height, by almost a point and lowered their blood glucose concentration after eating by almost 18 milligrams per deciliter. Experts suggest blood glucose after eating should remain below 180 milligrams per deciliter in people with diabetes.

Another nine weeks later, even with no additional intervention, these participants had maintained those health benefits, with the exception of an average slight gain in waist circumference among women.

The participants who waited nine weeks for the intervention recorded similar health improvements after they attended the education sessions.

But Miller noted that while they waited, this group also gained weight and recorded expansions of their waists – yet another sign that education can’t start soon enough for many patients with diabetes.

“They had a trajectory of change that was getting worse,” she said. “People with diabetes do need continued support to sustain optimal glycemic control because the disease progresses as they live longer.”

Based on self-reports of food choices, the study showed that participants’ fiber intake improved and they ate less fat. And they did not restrict carbohydrates, but instead made different carbohydrate choices.

“We were not putting people on a strict diet. They consumed the same amount of carbohydrate that they normally would, but selected lower glycemic-index foods within that carbohydrate allotment,” Miller said. “That addresses another controversy in nutrition. People with diabetes do not have to go on a low-carb diet, which typically is accompanied by a high intake of fat.

“What these participants ate was closer to the dietary guidelines generally recommend for Americans, with less than 30 percent of calories coming from fat. The quantity of carbohydrate does matter to some extent, but the type of carbohydrate makes a big difference.”

This research was supported by a Hertzler Grant for Intervention Research from the American Dietetic Association Foundation, the California Raisin Marketing Board and a grant from the National Institutes of Health. 

Co-authors of the study were Melissa Davis Gutschall, Diane Mitchell and Frank Lawrence, all of Pennsylvania State University.

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Contact: Carla Miller, (614) 292-1391; CMiller@ehe.osu.edu

Written by Emily Caldwell, (614) 292-8310; caldwell.151@osu.edu