Eating manners is considered a major factor in type 2 diabetes. Recently, ambient food temperature has attracted some attention in the understanding of diabetes in Asian populations. A study published in ’Nutrition and Diabetes’ investigated various responses of glucose-regulating hormones to cold and hot glucose solutions in normal subjects and subjects with type 2 diabetes.

The crossover, self-controlled study, normal subjects (N = 19) and patients with type 2 diabetes (N = 22) were included and randomly assigned to a hot (50 °C) or a cold (8 °C) oral glucose-tolerance test (OGTT). On the subsequent day, the cohort was switched to the OGTT at the other temperature. Blood glucose, insulin, GIP, glucagon-like peptide-1 (GLP-1), and cortisol were measured at 0, 5, 10, 30, 60, and 120 min during each OGTT. After the hot OGTT, all subjects ingested hot (>42 °C) food and water for that day, and ingested food and water at room temperature (≤24 °C) for the day after cold OGTT. All participants had continuous glucose monitoring (CGM) throughout the study.

The study revealed that compared to cold OGTT, blood glucose was significantly higher with hot OGTT in both groups (both P < 0.05). Insulin and GLP-1 levels were significantly higher in hot OGTT in normal subjects only (both P < 0.05). The GIP and cortisol responses did not differ with temperature in both groups. CGM showed that normal subjects had significantly higher 24-h mean glucose (MBG) (6.11 ± 0.13 vs. 5.84 ± 0.11 mmol/L, P = 0.021), and standard deviation of MBG with hot meals (0.59 ± 0.06 vs. 0.48 ± 0.05 mmol/L, P = 0.043), T2DM patients had higher MBG only (8.46 ± 0.38 vs. 8.88 ± 0.39 mmol/L, P = 0.022).

The authors summarized that compared with cold glucose solution, hot glucose solution increased the blood glucose, blood insulin levels, and GLP-1 levels. In patients with type 2 diabetes, GLP-1 response in hot OGTT was diminished for as yet unknown reasons.