Intragastric administration of the bitter tastant quinine lowers the glycemic response to a nutrient drink without slowing gastric emptying in healthy men.
Level 2 - randomized trial
Individual randomized double-blind crossover trial in humans
PubMed 31774306 · doi:10.1152/ajpregu.00294.2019
What was done
In a two-part, double-blind, randomized crossover trial, healthy lean men (mean age 26 ± 2 years) received intragastric infusions of quinine (275 mg, 600 mg, or control) on three separate visits, 30 minutes before a challenge. In Part A (n = 15), participants consumed a mixed-nutrient drink; plasma glucose, insulin, glucagon, and GLP-1 concentrations were measured at baseline, after quinine alone, and for 2 hours post-drink, alongside gastric emptying. In Part B (n = 12), participants received an ad libitum buffet meal to quantify energy intake.
What was found
Quinine alone (275 mg and 600 mg) modestly stimulated insulin secretion (P < 0.05). Following the nutrient drink, both doses significantly reduced plasma glucose and stimulated insulin compared with control (P < 0.05). Quinine at 275 mg significantly stimulated GLP-1 (P < 0.05), whereas 600 mg showed non-significant trends to stimulate GLP-1 (P = 0.066) and glucagon (P = 0.073). Quinine did not affect gastric emptying of the drink or energy intake at the buffet meal. Absolute concentrations and effect sizes were not reported in the abstract.
Why it matters
This study demonstrates that activating gut bitter-taste receptors with intragastric quinine lowers postprandial blood glucose in humans, an effect driven by incretin and insulin secretion rather than delayed gastric emptying.
Limits
The study had a small sample size restricted entirely to young, healthy, lean men, limiting generalizability to females or populations with type 2 diabetes and obesity. It evaluated only acute, single-dose effects, and the abstract omits quantitative baseline and postprandial values. Quinine failed to demonstrate any reduction in energy intake.
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