Metabolic response to cereal fiber supplementation in subjects with prediabetes is depending on baseline glycemic and anthropometric status (OptiFiT)

Aims:

Within the Optimal Fibre Trial, intake of insoluble oat fibers was shown to significantly reduce glycemia. This effect might be modulated by presence or absence of impaired glycemic response and/or obesity (Hjorth et al., 2017, DOI: 10.3945/ajcn.117.155200, 10.1002/oby.22004). The OptiFiT cohort is appropriate for a stratified analysis.

Methods:

180 Caucasian participants with impaired glucose tolerance (IGT) were double-blindly randomized between twice daily insoluble, little fermentable oat fiber (15 g/day) taken as a drink or placebo supplementation for 2 years (n = 89 and 91, respectively). Once yearly, they underwent fasting blood sampling, oGTT and full anthropometry.

At baseline, out of 136 subjects (PP), 72 (54%) showed additionally impaired fasting glucose (IFG) and 87 were (62%) classified as obese (BMI> 30).

Based on those two parameters, we performed a stratified per-protocol and intention-to-treat analysis of metabolic effects.

Results:

The NFG+IGT (n = 64) as well as the non-obese subgroup (n = 49) did not show significant differences between fiber and placebo groups concerning metabolic, anthropometric and inflammatory parameters.

Within the IFG+IGT stratum (n = 72), 2-h glucose, CRP, HbA1c and GGT decreased significantly stronger in the fiber group (adjusted for weight change).

In obese subjects (n = 87), a significant superiority for fiber intervention was present regarding change in HbA1c and leukocyte count.

An ITT analysis did not reveal any results differing from PP analysis.

Conclusions:

Cereal fiber improves glycemic metabolism, with pronounced effectiveness in subjects with impaired fasting glucose and/or obesity. Cereal fiber supplementation in staple food should be considered as a treatment option.