The Effect of Soluble Fiber to Reduce Post-prandial Glycemic Excursion in Adults With Cystic Fibrosis

With improved survival, the clinical spectrum of cystic fibrosis (CF), a complex multi systemic disease, continue to evolve. A major emerging complication is CF related diabetes (CFRD). CFRD is a major co-morbidity occurring in 20% of adolescents and 40-50% of adults and is mainly due to reduced insulin secretion. Patients who develop CFRD are at increase risk of morbidity and mortality and they are also facing an increased medical burden with insulin therapy, the only recommended treatment. Because accelerated decline in weight and/or pulmonary function start 2 to 4 years before CFRD onset and that this period is characterized by frequent Post-Prandial Glycemic (PPG) excursions, the role of these PPG excursions in clinical deterioration have been investigated. The investigators have shown that higher PPG excursions are associated with lower pulmonary function and others have shown that PPG excursions predicts future CFRD risk. Food overconsumption is discouraged in other forms of diabetes to avoid overweight or obesity, but also to prevent an increase in insulin demand. In contrast, nutritional approach for patients with CF focuses on high-energy high-fat diet to meet increased energy requirements. In combination with an appropriate pancreatic enzyme supplementation, this approach contributes significantly to the improved nutritional status, lung function and survival of patients. However, such diet also contributes to increased PPG excursions. Based on the beneficial effects of nutrition therapy to improve PPG in other forms of pre-diabetes and diabetes, extending such benefits to patients with CF is important. In the context of high CF treatment burden, such approach should however be simple and not inducing weight loss. The investigators aim to test the feasibility and the effectiveness of a viscous fiber supplement to reduce PPG in adult patients with CF. Using a randomized crossover design, the investigators will study the impact of two doses of a viscous fiber supplement as compared to a placebo in controlled conditions, in 22 patients, over 8 hours, at the research center with 2 standardized mixed-meals: breakfast and lunch on PPG excursions.