Challenges in the dietary treatment of cystic fibrosis related diabetes mellitus

Cystic fibrosis related diabetes mellitus is an increasingly recognized problem as survival in patients with cystic fibrosis improves. In a 5 year retrospective study of 627 children and adults attending Toronto cystic fibrosis clinics, we identified 57 (9%) patients with cystic fibrosis related diabetes mellitus; four (1.3%) of 301 children (<18 years) and 53 (16%) of 326 adults. The development of this complication of cystic fibrosis is associated with increased mortality, deteriorations in both respiratory and nutritional status, and the development of late microvascular, but not macrovascular, diabetic complications. Unfortunately, systematic review of the literature provides few well designed studies that provide sound evidence for clinical practice. Recommendations are therefore often based on anecdote, rather than physiological or outcomes research. Dietary therapy combines the principles of the dietary management of both cystic fibrosis and diabetes mellitus, but emphasizes the need for a high energy diet (> 100% of recommended daily intake) in patients with cystic fibrosis related diabetes mellitus. The importance of calories from fat is emphasized, with no restriction on total carbohydrate intake. Insulin intake mirrors carbohydrate intake. Routine dietary therapy is straightforward, but challenges occur due to both complications of cystic fibrosis and advancing disease. If a patient with cystic fibrosis related diabetes mellitus is malnourished, overnight enteral tube feeding is often used, with an adjusted insulin regimen. There is a great need for both physiological and outcomes research to provide sound scientific evidence for the dietary treatment of cystic fibrosis related diabetes mellitus. (C) 2000 Harcourt Publishers Ltd.