Roasting intensity of naturally low-caffeine Laurina coffee modulates glucose metabolism and redox balance in humans

Coffee consumption is negatively associated with risk of type 2 diabetes and cardiovascular mortality. Coffee roasting can greatly modify the quality-quantitative characteristics of bioactive compounds. We compared the effects of two different roasting intensities of the same naturally low-caffeine Arabica coffee variety (Laurina) on glucose and lipid metabolism as well as oxidative stress.We performed a double-blind, crossover intervention study. Fourteen healthy male volunteers consumed four cups daily of light roasted coffee (LRC) and dark roasted coffee (DRC), each for 1 wk (intervention period 1 and 2 respectively). One wk washout, with total abstinence from coffee and other possible caffeine sources, preceded each intervention. Data were collected at the end of washout and intervention periods.Changes between washout and intervention periods in glucose concentrations at 2 h post–oral glucose tolerance test, were significantly lower after DRC than LRC intake (−0.6 ± 0.3 and 0.4 ± 0.3 mmol/L, P < 0.03). Changes in β-cell function, assessed as insulin secretion-sensitivity index-2, were significantly greater after DRC than LRC (34.7 ± 25.0 and −18.8 ± 21.0, P = 0.03). The initial (30 min) post–oral glucose tolerance test area under the curve of glucagon-like peptide-1 was 24± 9% greater (P = 0.03) after DRC than LRC. LRC or DRC did not affect insulin sensitivity. Changes from basal of reduced-to-oxidized glutathione ratio (GSH/GSSG) in erythrocytes were significantly greater after DRC than LRC (+1437 ± 371 and −152 ± 30, P < 0.05). The omega-3 index in erythrocyte membranes was 16± 4% greater (P < 0.001) after DRC than LRC.DRC consumption improved postload glucose metabolism by increasing incretin and insulin secretions. DRC compared to LRC improved redox balance and increased omega-3 fatty acids. Thus, we suggest greater metabolic benefits related to DRC.