Granola Bar Not Enough to Prevent Exercise-Induced Blood Glucose Drop in Type 1 Diabetes

October 01, 2013

By Anne Harding

NEW YORK (Reuters Health) Oct 01 - Blood glucose drops sharply in type 1 diabetes patients on intensified insulin regimens with even moderate exercise, according to new findings presented last week in Barcelona at the European Association for the Study of Diabetes' annual meeting.

And supplementation with 10, 20, or 40 grams of carbohydrate from a granola bar was not enough to prevent patients from developing hypoglycemia, Dr. Michael Nauck, head of the Diabeteszentrum Bad Lauterberg in Germany and one of the study's authors, told Reuters Health.

"Until now everyone believed that this should be sufficient to prevent any reduction in glucose and hypoglycemia, and it didn't," he said.

Dr. Nauck and his team tested the effects of different amounts of carbohydrate supplementation in type 1 diabetes by using a prospective cross-over design. Twenty-four patients on intensified insulin regimens participated in one afternoon session without physical activity and three afternoon sessions in which they hiked 4 kilometers (about 60 minutes of walking). In random order on physical activity afternoons, the study participants had either no additional carbohydrates; 10 grams of carbohydrates; or 20 grams of carbohydrates at the beginning of the hike and 30 minutes later. The investigators tested study participants' blood glucose five times throughout the day.

No matter what type of carbohydrate regimen patients were given, their blood glucose fell to the same degree, from an average of 175 mg/dL at 2 p.m., when the walk began, to 100-110 mg/dL at 2:30 p.m.

Hypoglycemic episodes that occurred during and after exercise were often asymptomatic, and only detected by blood glucose testing. This is likely because sweating and an increased heart rate occur with both physical activity and low blood glucose, Dr. Nauck said. "During physical activity you probably cannot detect symptomatic episodes of hypoglycemia," he said. "Probably you just have to take your blood sugar every once in a while while you are exercising, otherwise you will never know."

While he and his colleagues expected blood glucose to drop with exercise, "everyone was surprised about the magnitude," he said. "The diabetes world until now had not known about that."

Based on the findings, Dr. Nauck said, people with type 1 diabetes who are on intensified insulin regimens should consume some rapidly absorbable carbohydrates before exercise, for example fruit juice or Coke. "Usually all these sweetened drinks have 10 grams of carbohydrates per 100 milliliters, and we believe you should have at least 200 maybe even 300 milliliters of such a drink," he said.

And with more-intense, longer-duration exercise, more compensation is likely needed, he added.

"This is a rather rough recommendation giving a broad range because it is different from person to person," Dr. Nauck said. For example, fitness level and body weight are both likely to affect the amount of glucose compensation a person needs, he said. And when someone exercises soon after a meal, he said, it is likely better to reduce the insulin dose given with the meal, rather than adding supplementary glucose.

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