Diabetes researchers look at pizza to find slow and steady insulin delivery wins the race

May 3 2005

With its doughy, carbohydrate-dense crust and high fat content, pizza can wreak havoc in people with diabetes. A Penn State Diabetes Center study suggests a slow and steady insulin-dosing pattern may best combat the glucose-raising effects of that common favorite food.

"Keeping glucose levels from jumping too high or dipping too low may help to reduce the risk of cardiovascular disease, which has been connected to erratic glucose levels in those with diabetes," said Robert Gabbay, M.D., Ph.D., associate professor of medicine, Penn State College of Medicine, Penn State Milton S. Hershey Medical Center, and co-director, Penn State Diabetes Center. "Our study shows that after a high carbohydrate, high fat meal like the pizza used in this study, spacing out insulin given by an insulin pump in two doses, one of which is over an eight-hour period, may keep glucose levels in a more favorable range than a single dose of insulin or a double dose taken over a shorter period."

This study titled, "Optimal Insulin Pump Dosing and Postprandial Glycemia Following a Pizza Meal Using the Continuous Glucose Monitoring System," was published in the April issue of Diabetes Technology & Therapeutics.

The study was initiated thanks to Susan M. Jones, M.S., C.R.N.P., C.D.E., a nurse practitioner, and Jill L. Quarry, M.S., R.D., L.D.N., C.D.E., a dietitian, both of whom noted problems with their diabetes patients.

"We noticed that it was very difficult for those with diabetes who were using insulin pumps to maintain good glucose values when they ate pizza," Jones said. "Because pizza is a favorite food for so many people and good quality of life is eating what you want every now and again, we suggested a study to see how best to help those with diabetes enjoy this common favorite food while maintaining good glucose levels."

Twenty-six volunteers with type 1 diabetes were selected from the patient population at Penn State Hershey Medical Center and were outfitted with a new glucose monitoring system (CGMS®, Medtronic Minimed, Northridge, Ca.) that averages blood glucose levels every five minutes. For three days, volunteers ate an evening meal of plain cheese pizza with water. The size of the meal was based on the usual amount the person would eat, usually two or three slices, but was weighed and consistent each night.

Insulin amounts were based on the person's known individual needs and the amount was kept consistent each of the three days. The timing of the administration of the insulin, however, was varied each day. On day one, all of the insulin was given immediately prior to eating the meal. On day two, half of the insulin was given in one dose immediately before the meal with the other half given slowly via the continuous insulin pump over the subsequent four hours. On day three, half of the insulin was given in one dose immediately before the meal, and the other half was administered slowly via the pump over the following eight hours. Volunteers ingested nothing but water in the evenings after the pizza meal and maintained their normal diets throughout the rest of the day.

Mean glucose levels after eating the pizza were 133 mg/dl for the day one single dose of insulin, 145 mg/dl for the two-stage, four-hour administration of insulin, and 104 mg/dl for the two-stage, eight-hour administration of insulin. The suggested target glucose range is typically between 80 mg/dl and 124 mg/dl.

"This study is the first to examine the optimal timing of the dual-wave administration of insulin," Gabbay said. "We showed that the eight-hour extended dose of insulin better controlled post-meal glucose levels and did not decrease glucose levels enough to cause any hypoglycemic events, which is unusual. Blood glucose control after a pizza meal was improved by extending the time of delivery of insulin to eight hours without varying the total amount of insulin administered."

Gabbay cautions that this method of insulin delivery may not be applicable to all high-carbohydrate, high-fat foods.

"Pizza is a complex food and causes prolonged post-meal hyperglycemia," he said. "For now, generalization to food types other than pizza may best be based on foods that are known to cause the same type of prolonged hyperglycemia and not necessarily those that have only the same composition."

Gabbay said future studies will investigate whether the method works with foods of other compositions.

In addition to Gabbay, Jones and Quarry, the study team included Molly Caldwell-McMillan, M.D., Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, and David T. Mauger, Ph.D., Department of Health Evaluation Science, Penn State College of Medicine, Penn State Hershey Medical Center. This study was funded in part by Medtronic Minimed, Northridge, CA.

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