Prebiotic Inulin Supplementation and Peripheral Insulin Sensitivity in adults at Elevated Risk for Type 2 Diabetes: A Pilot Randomized Controlled Trial
What this study found
Inulin did not improve peripheral insulin sensitivity or skeletal muscle metabolic flexibility versus placebo after 6 weeks on a controlled diet; insulin sensitivity indices (SI, Sg, AIRg, DI) unchanged; fasting insulin decreased with inulin but not after adjusting for baseline; HOMA-IR reductions were not significant after adjustment; no changes in glucose oxidation, fat oxidation, or substrate metabolism; Bifidobacteria increased with inulin; intestinal permeability and endotoxin remained unchanged; conclusion: inulin supplementation at 10 g/day for 6 weeks does not improve glucose…
- Study & population
- Randomized, double-blind, placebo-controlled feeding trial; adults aged 40–75 years with BMI 25–39.9 kg/m^2, overweight/obese at increased risk for type 2 diabetes; 24 randomized, 22 completed; predominantly female and Caucasian.
- Intervention
- Inulin 10 g/day vs maltodextrin placebo 10 g/day for 6 weeks; taken at breakfast dissolved in 16 oz water.
- Key limitation
- IVGTT data available for only 8 placebo and 9 inulin participants; small sample size (24 randomized, 22 completed); racially homogeneous and mostly female; short duration (6 weeks); controlled feeding with weight stability may limit generalizability; baseline fasting insulin higher in the inulin group; effects…
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Open PDFOriginal abstract
Prediabetes affects 84.1 million adults, and many will progress to type 2 diabetes (T2D). The objective of this proof-of-concept trial was to determine the efficacy of inulin supplementation to improve glucose metabolism and reduce T2D risk. Adults (n = 24; BMI: 31.3 ± 2.9 kg/m2; age: 54.4 ± 8.3 years) at risk for T2D were enrolled in this controlled feeding trial and consumed either inulin (10 g/day) or placebo (maltodextrin, 10 g/day) for six weeks. Assessments included peripheral insulin sensitivity, fasting glucose, and insulin, HOMA-IR, in vivo skeletal muscle substrate preference, Bifidobacteria copy number, intestinal permeability, and endotoxin concentrations. Participant retention was 92%. There were no baseline group differences except for fasting insulin (p = 0.003). The magnitude of reduction in fasting insulin concentrations with inulin (p = 0.003, inulin = Δ-2.9, placebo = Δ2.3) was attenuated after adjustment for baseline concentrations (p = 0.04). After adjusting for baseline values, reduction in HOMA-IR with inulin (inulin = Δ-0.40, placebo=Δ0.27; p = 0.004) remained significant. Bifidobacteria 16s increased (p = 0.04; inulin = Δ3.1e9, placebo = Δ-8.9e8) with inulin supplementation. Despite increases in gut Bifidobacteria, inulin supplementation did not improve peripheral insulin sensitivity. These findings question the need for larger investigations of inulin and insulin sensitivity in this population.