Supplementary Material for: A Randomised Crossover Trial: The Effect of Inulin on Glucose Homeostasis in Subtypes of Prediabetes

Background: Fermentable carbohydrates (FCHO) have been shown to improve insulin sensitivity in normoglycaemic and insulin-resistant subjects. However, there are no data on subjects with prediabetes. We aimed to investigate the effect of the FCHO inulin, on glucose homeostasis in subjects with prediabetes. Methods: In a double-blind and placebo-controlled crossover study, 40 volunteers with prediabetes were randomly allocated to take 30 g/day of inulin or cellulose for 2 weeks in a crossover trial, following a 4-week dose-escalation run-in. Fasting insulin and glucose were measured for all subjects. Fifteen of the 40 subjects also underwent a meal tolerance test to assess insulin sensitivity, free fatty acids and glucagon-like peptide-1 concentrations. A subanalysis was carried out to examine any differences between the prediabetes subtypes. Results: Inulin was associated with a significant increase in (0-30 min)incremental AUC (iAUC) for insulin (treatment: p < 0.04) and (0-60 min)iAUC for insulin (treatment: p < 0.04) compared to control. There was a significant reduction in insulin resistance measured by the homeostatic model assessment in the isolated-impaired fasting glucose (p < 0.05) but not in the isolated-impaired glucose tolerance groups (p = 0.59). Conclusion: The FCHO, inulin, may have unique metabolic effects that are of particular benefit to people at risk of diabetes, which warrant further investigation.