AMSTERDAM — Patients with type 1 diabetes often underestimate the amount of carbohydrates in their meals, Dr. Guido Freckmann reported at the annual meeting of the European Association for the Study of Diabetes.
The ability to accurately estimate the carbohydrate content is key to a patient's efficacy in making appropriate therapy decisions with insulin pump or basal-bolus insulin injection regimens. It is therefore of concern that underestimation by about 25% was typical in this study of 74 such patients, with warm meals and large meals presenting even greater potential for error, said Dr. Freckmann, of the Institute for Diabetes Technology in Ulm, Germany.
The study included 38 men and 36 women with a mean age of 44 years and mean diabetes duration of 21 years. Their mean hemoglobin A1c level was 7.2%. Twenty-six were on multiple daily injections and 48 were on insulin pump therapy.
Patients were given 24 different test meals—11 warm and 13 cold—in random order, including 8 breakfasts, 8 lunches, and 8 dinners ranging in carbohydrate content from 55 g to 164 g. Among the meals were a breakfast of rye bread, roll, margarine, ham sausage, Camembert, and yogurt containing 82 g of carbohydrate; a pizza lunch including mozzarella, basil, olive oil, and fruit, adding up to 138 g of carbs; and a dinner of baguette, tomato, mozzarella, and olive oil totaling 101 g of carbs.
Patients estimated the carbohydrate content of the meals to be a median of 75% compared with the actual content; estimates ranged from 53% to 127%. Warm meals prompted even more carb underestimation than cold (72% vs. 77%), and large meals were underestimated to a greater degree than were smaller meals, Dr. Freckmann reported.
Possible reasons include the fact that patients often don't count the carbs of vegetables and other low-carb items. It's also possible that some patients might compensate for the underestimate by adapting their individual insulin-to-carb ratio, thereby giving themselves sufficient insulin doses despite the carb underestimate, he said.
On the positive side, the degree of correct estimation was significantly improved—from 73% to 83%—among 35 patients who received training in carb counting.