We used a sophisticated thermosensor to measure both core (eardrum) and extremity (toe) temperature, and then took the average values to compare the four conditions across thirteen subjects. We found that carbonated water had a significant effect on decreased extremity temperature over still water. More importantly, the effects were apparent the minute the carbonation hit the mouth. Heart rate measurements taken to examine autonomous nervous system function also revealed a temporary increase just with mouth stimulation—an increase that was significant compared to the other three conditions. These results suggest that mouth stimulation from carbonated water signals the brain and the autonomic nervous system, effectively decreasing extremity temperature while increasing heart rate.

Both cold carbonated water and cold still water lower the body temperature when swallowed. However, we found that the sensory stimulation caused by carbonated water in the mouth produces additional effects that decrease body temperature. Drinking carbonated water in addition to wearing cooler clothes can thus help alleviate discomfort during the hot summer months—which is great news for office energy conservation efforts!