Ice slurry ingestion reduces human brain temperature measured using non-invasive magnetic resonance spectroscopy

We previously reported that ice slurry ingestion reduced forehead skin temperature, thereby potentially reducing brain temperature (T_brain). Therefore, in the current study, we investigated the effect of ice slurry ingestion on T_brain using proton magnetic resonance spectroscopy, which is a robust, non-invasive method. Eight male participants ingested 7.5 g/kg of either a thermoneutral drink (37 °C; CON) or ice slurry (-1 °C; ICE) for about 5 min following a 15-min baseline period. Then, participants remained at rest for 30 min. As physiological indices, T_brain, rectal temperature (T_re), mean skin temperature, nude body mass, and urine specific gravity were measured. Subjective thermal sensation (TS) and thermal comfort (TC) were measured before and after the experiment. T_brain and T_re significantly reduced after ingestion of ICE compared with after ingestion of CON, and there was a significant correlation between T_brain and T_re. The other physiological indices were not significantly different between beverage conditions. TS and TC were significantly lower with ICE than with CON (p < 0.05). These results indicate that ice slurry ingestion can cool the brain, as well as the body's core.