A Single Sauna Session Does Not Improve Postprandial Blood Glucose Handling in Individuals with Type 2 Diabetes Mellitus: A Cross-Over, Randomized, Controlled Trial

Abstract

Introduction Passive heat treatment has been suggested to improve glycaemic control in individuals with type 2 diabetes mellitus. Previous studies have predominantly focused on hot water immersion and traditional sauna bathing, as opposed to the more novel method of infrared-based sauna bathing. Here we assessed the impact of a single infrared sauna session on post-prandial glycaemic control in older individuals with type 2 diabetes mellitus. Methods In this randomized controlled crossover trial, 12 participants with type 2 diabetes mellitus (male/female: 10/2, age: 69±7 y, BMI: 27.5±2.9 kg/m2) rested in an infrared sauna twice: once in a heated condition (60°C) and once in a thermoneutral condition (21°C) for 40 min, immediately followed by a 2-h oral glucose tolerance test (OGTT). Venous blood samples were obtained to assess plasma glucose and insulin concentrations and to determine the whole-body composite insulin sensitivity index. Results Body core and leg skin temperature were higher following the heated condition compared to the thermoneutral condition (38.0±0.3 vs 36.6±0.2°C and 39.4±0.8 vs 31.3±0.8°C, respectively; P<0.001 for both). The incremental area under the curve (iAUC) of plasma glucose concentrations during the OGTT was higher after the heated condition compared to the thermoneutral condition (17.7±3.1 vs 14.8±2.8 mmol/L/120 min; <i>P</i><0.001). No differences were observed in plasma insulin concentrations (heated: 380±194 vs thermoneutral: 376±210 pmol/L/120 min; <i>P</i>=0.93) or whole-body composite insulin sensitivity indexes (4.5±2.8 vs 4.5±2.1; <i>P</i>=0.67). <b>Conclusions</b> A single infrared sauna session does not improve postprandial blood glucose handling in individuals with type 2 diabetes mellitus. Future studies should assess the effect of more prolonged application of infrared sauna bathing on daily glycaemic control.