Oral Cooling and Carbonation Increase the Perception of Drinking and Thirst Quenching in Thirsty Adults

Fluid ingestion is necessary for life, and thirst sensations are a prime motivator to drink. There is evidence of the influence of oropharyngeal stimulation on thirst and water intake in both animals and humans, but how those oral sensory cues impact thirst and ultimately the amount of liquid ingested is not well understood. We investigated which sensory trait(s) of a beverage influence the thirst quenching efficacy of ingested liquids and the perceived amount ingested. We deprived healthy individuals of liquid and food overnight (> 12 hours) to make them thirsty. After asking them to drink a fixed volume (400 mL) of an experimental beverage presenting one or two specific sensory traits, we determined the volume ingested of additional plain, ‘still’, room temperature water to assess their residual thirst and, by extension, the thirst-quenching properties of the experimental beverage. In a second study, participants were asked to drink the experimental beverages from an opaque container through a straw and estimate the volume ingested. We found that among several oro-sensory traits, the perceptions of coldness, induced either by cold water (thermally) or by l-menthol (chemically), and the feeling of oral carbonation, strongly enhance the thirst quenching properties of a beverage in water-deprived humans (additional water intake after the 400 ml experimental beverage was reduced by up to 50%). When blinded to the volume of liquid consumed, individual’s estimation of ingested volume is increased (~22%) by perceived oral cold and carbonation, raising the idea that cold and perhaps CO2 induced-irritation sensations are included in how we normally encode water in the mouth and how we estimate the quantity of volume swallowed. These findings have implications for addressing inadequate hydration state in populations such as the elderly.

体液摄入是生命存续的必要条件，口渴感知是驱动个体饮水的核心动机。已有研究证实，口咽部刺激对动物与人类的口渴感受及摄水量存在影响，但此类口腔感官信号如何作用于口渴感知，并最终影响液体摄入量，目前尚未得到充分阐明。我们针对实验饮料的何种感官特征能够影响摄入液体的解渴功效，以及个体对摄入液体量的主观感知这一问题展开了研究。我们将健康受试者隔夜禁食禁水（时长超过12小时），使其处于口渴状态。随后让受试者饮用固定体积（400 mL）的实验饮料，该饮料仅具备一种或两种特定感官特征。之后，我们通过测量受试者额外饮用的常温无气清水体积，来评估其残余口渴程度，并以此间接推断实验饮料的解渴性能。在第二项实验中，受试者通过吸管从不透明容器中饮用实验饮料，并对其摄入的液体体积进行主观估算。我们发现，在多项口腔感官特征中，由冷水（热学途径）或左旋薄荷醇（化学途径）介导的口腔冷感，以及口腔碳酸化感受，能够显著增强缺水状态下人类受试者的饮料解渴功效——在饮用400 mL实验饮料后，受试者额外摄水量最多可降低50%。当受试者对自身已摄入的液体体积不知情时，口腔冷感与碳酸化感受会使其对摄入体积的主观估算值提升约22%，这提示我们，冷感乃至二氧化碳诱导的刺激感，均参与了我们对口腔内水分的编码过程，以及对吞咽液体体积的主观估算机制。上述研究结果可为解决老年群体等人群的水合不足问题提供理论参考。