Summary: A new study finds that oral sensations of coldness and carbonation help reduce thirst and can influence how much people drink.
Source: Monell Chemical Senses Center.
Understanding the sensory triggers that relieve thirst could improve hydration strategies for at-risk groups.
Researchers at the Monell Chemical Senses Center, together with collaborators, report that sensations of oral coldness and carbonation significantly reduce the subjective feeling of thirst. Because thirst relief and its timing play a major role in how much fluid a person consumes, these findings point to sensory-based approaches that may help increase fluid intake in populations at higher risk for dehydration, such as older adults, military personnel, and athletes.
Dehydration happens when the body loses more fluid than it takes in. Mild to moderate dehydration commonly causes thirst and headaches; severe dehydration requires prompt medical attention. People who are especially vulnerable include the elderly, soldiers in the field, athletes during intense activity, and manual laborers in hot environments.
“We have a good sense of what triggers thirst, but we need a clearer picture of what turns it off so we can better encourage at‑risk individuals to keep drinking,” said Paul A.S. Breslin, PhD, the study’s senior author and a sensory biologist at Monell.
Although rehydration ultimately relieves thirst, the sensation of thirst is often quenched and drinking stops long before the consumed liquid is absorbed into the bloodstream. Sensory signals in the mouth appear to play a key role in signaling that enough liquid has been taken. However, precisely which oral cues inform the brain about how much has been consumed has not been fully understood.
Published in the open access journal PLOS ONE, the study set out to identify which oral sensations affect thirst and alter subsequent drinking behavior.
Ninety‑eight healthy adults aged 20 to 50 participated. To ensure a strong thirst drive, participants fasted from food and drink overnight, then ate a light breakfast of toast and jelly. At that point they reported feeling strongly thirsty. Each participant was then given five minutes to drink 400 ml (13.5 oz) of an experimental beverage under one of four conditions: room-temperature plain water, cold plain water, room-temperature carbonated water, or cold carbonated water.
After a short break, participants were offered plain, room-temperature, non-carbonated water and allowed to drink as much as they wished. The volume consumed during this second, unrestricted phase served as a functional measure of how effectively the initial experimental beverage had quenched their thirst.
Results showed that a cold beverage relieved thirst more effectively than a room-temperature drink. Adding carbonation to a cold beverage produced an additional, measurable decrease in the amount of plain water participants drank afterward. In follow-up tests, other oral qualities—such as astringency, sweetness, or mild acidity—did not alter drinking behavior, supporting a specific role for perceived cold and carbonation in thirst reduction.
In a separate experiment, researchers produced the sensation of cold chemically, using l‑menthol, while serving water at room temperature. Menthol produced a thirst‑quenching effect comparable to that of genuinely cold water. “This indicates that it is the perceived coolness in the mouth that influences thirst relief, rather than temperature alone,” said Catherine Peyrot des Gachons, PhD, study lead and sensory biologist at Monell.
The investigators also tested whether oral cold and carbonation change people’s perception of how much they have drunk. When participants consumed experimental beverages from an opaque container and could not see the volume, sensations of cold and carbonation led them to estimate having consumed a larger volume—about 22% higher—than the actual amount. Combined with the reduced subsequent water intake observed in the main experiment (up to a 50% reduction), these results suggest that cold and carbonation are integrated into the oral encoding of drinking and influence both perceived and actual hydration behavior.
Breslin highlighted the broader implications: “Thirst signals a physiological need, but stopping drinking depends on sensory information that the brain integrates. Understanding those sensory cues gives us tools to design beverages or strategies that could help people maintain proper hydration.”
Contributors to the study included Michael Gleason and Siyu Zhang of Monell; Julie Avrillier of Monell and AgroSup Dijon Institut National Superieur, Dijon, France; Laure Algarra of Monell and AgroParisTech, Paris, France; and Emi Mura and Hajime Nagai of Suntory Global Innovation Center Limited, Osaka, Japan. Dr. Breslin also holds an appointment at Rutgers University School of Environmental and Biological Sciences.
Funding: The research received partial funding from a grant by the Suntory Global Innovation Center. Apart from the direct research contributions of authors Emi Mura and Hajime Nagai, Suntory did not participate in study design, data analysis, or interpretation.
Competing Interests: The authors have declared that no competing interests exist.
Abstract
Oral Cooling and Carbonation Increase the Perception of Drinking and Thirst Quenching in Thirsty Adults
Fluid intake is essential, and thirst is a primary motivator to drink. Oropharyngeal stimulation influences thirst and water intake, but the specific oral sensory cues that determine thirst relief and the amount consumed are not fully known. In this study, healthy adults deprived of food and liquid overnight drank a fixed volume (400 mL) of beverages designed to present specific sensory traits. Subsequent intake of additional plain, room‑temperature water served as a measure of residual thirst. The perceptions of coldness—whether produced thermally by cold water or chemically by l‑menthol—and the sensation of carbonation substantially enhanced the thirst‑quenching effects of a beverage, reducing subsequent water intake by up to half. When blind to consumed volume, perceived cold and carbonation also increased subjects’ estimates of how much they had drunk by about 22%. These findings suggest that oral cold and carbonation cues are incorporated into how humans encode drinking and estimate swallowed volume, with implications for improving hydration in vulnerable populations.
Study: “Oral Cooling and Carbonation Increase the Perception of Drinking and Thirst Quenching in Thirsty Adults” by Catherine Peyrot des Gachons et al., published online September 29, 2016 in PLOS ONE. DOI: 10.1371/journal.pone.0162261