The study aimed at assessing the effect of a decaffeinated green coffee extract, rich in hydroxycinnamates, oat beta-glucans or the combination of both bioactive compounds on overweight/obese subjects with hyperglycemia.

In a randomized, crossover, blind, three-arm study, volunteers consumed twice a day a nutraceutical providing 5 g/d beta-glucan (BG), 600 mg/d green coffee polyphenols (GC) or a combination of both (5 g/d BG + 600 mg/d GC). Each intervention stage lasted 8 weeks and was followed by a 4-week wash-out.

Blood, urine and fecal samples were obtained at the beginning and end of each intervention stage. Blood pressure, oral glucose tolerance test (OGTT) and body composition (body weight, anthropometry, bioimpedance) were measured at each control visit. Physical activity was controlled by accelerometry (1 week during each intervention stage). Energy expenditure was measured by calorimetry. Food intake was monitored by 3-d food records. Satiety was determined by subjective (VAS) and objective (weighting consumed food) records after consuming the nutraceutical during each intervention stage.

In a subset of volunteers (9), a pharmacokinetic study was performed to assess bioavailability and metabolism of polyphenols at the beginning and end of each intervention (GC and GC+BG only). In these volunteers, blood was taken at different times during 24 h; urine samples were also collected at different intervals during 24 h, and feces were obtained at 0 and 24 h approximately after consuming the nutraceuticals containing GC. A targeted metabolomic analysis was carried out in these samples. In these volunteers, incretins and hormones were also determined in blood samples.

Inclusion Criteria:

• Men and women, with BMI between 25-35 kg/m2
• Fasting blood glucose between 6,11-6,94 mmol/L (110-125 mg/dL) and/or
• Blood glucose between 7,77-11,04 mmol/L (140-199 mg/dL) 2 h after an oral glucose overload

Exclusion Criteria:

• Having other chronic pathologies different from overweight/obesity and prediabetes.
• On prescription drugs, hormones or dietary supplements (e.g. dietary fibre, pollen, vitamin complexes, etc.)
• Vegetarian
• Smoking
• Known hypersensibility/allergy to any of the tests products
• Pregnant women
• On dietary regimen or physical training to lose weight

Nutraceutical was provided in aluminum foil sachets marked A, B or C for blinding to participants. Aroma and flavor compounds were added to ensure similar organoleptic properties of the 3 nutraceuticals tested.