Background: Enteral formula feedings are frequently prescribed to cystic fibrosis (CF) patients to boost caloric intake. A substantial number of these patients are glucose intolerant and have severe respiratory compromise. Methods: To determine the effect of the carbohydrate content on glucose tolerance and respiratory function in glucose-intolerant CF patients with poor lung function, we examined the response to bolus feedings of five dietary supplements: a high-fat formula developed in our Clinical Research Center (CRC), Pulmocare, a high-carbohydrate formula developed in our CRC, Ensure Plus, and sugar-free Scandishake. Results: Glucose excursion in response to the formulas with the lowest carbohydrate content was significantly less than that found in response to formulas with higher carbohydrate content. Insulin levels were also markedly lower in response to the low-carbohydrate high-fat formulas. Glucose excursion, expressed as a percent of the response to the CRC high-fat formula, was 111% ± 12% for Pulmocare (p = NS), 202% ± 34% for Ensure Plus (p < .01), 227% ± 37% for CRC high carbohydrate (p = .001), and 357% ± 33% for sugar-free Scandishake (p < .001). CO2 production, O2 consumption, minute ventilation, and respiratory rate increased modestly but not significantly in response to all formulas. No significant differences were found between the formulas in regards to these parameters. There were no subjective complaints of dyspnea during any of the five studies. Conclusion: The carbohydrate content of liquid dietary supplements appears to be an important determinant of hyperglycemia in glucose-intolerant adult CF patients.
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