Dietary fiber intakes and insulin requirements in pregnant women with type 1 diabetes

OBJECTIVE: To determine whether higher dietary fiber intake (water soluble and insoluble) is associated with lower insulin requirements and better glycemic control in pregnant women with type 1 diabetes consuming a self-selected diet. DESIGN: A longitudinal, observational study. SUBJECTS: Pregnant women (n=141) with type 1 diabetes participating in an interdisciplinary program examining the effects of glycemic control on pregnancy outcome (Diabetes and Pregnancy Program, University of Cincinnati Medical Center). MEASUREMENTS: We determined total, water soluble and insoluble fiber intakes from 3-day food records kept each trimester during pregnancy. Outcome measures were insulin dose, pre-meal blood glucose, and glycated hemoglobin concentrations. STATISTICAL ANALYSES: Correlation coefficients, multiple regression, mixed-model analysis of variance. RESULTS: Mean intakes (g/day) of total, water soluble fiber, and insoluble fiber were 14.0 (range, 1.8-33.1), 4.8 (range, 0.6-10.5) and 9.0 (range, 1.1-24.0), respectively. In the second and third trimesters of pregnancy, insulin requirements were inversely associated with total, water soluble, and insoluble fiber intakes; the correlation coefficients ranged from -0.22 to -0.17 (P=.02 to .08). Insulin requirements associated with a higher fiber intake (20.5 g/day) were 16% to 18% lower than for a lower fiber intake (8.1 g/day). These relations remained after adjustment for body weight, disease severity and duration, insulin type, and study year in the second (P=.03 to .10) but not in the third trimester. Pre-meal blood glucose and glycated hemoglobin concentrations were not associated with fiber intake. CONCLUSIONS: Among pregnant women with type 1 diabetes, higher fiber intake is associated with lower daily insulin requirements. Dietary fiber intake should be considered when counseling patients about the management of blood glucose concentrations.