12 January - 20 June 2016

Sensory qualities that best quench thirst

Findings from a study by Monell Center and collaborators could guide sensory approaches to increase fluid intake in populations at risk from dehydration, including the elderly, soldiers, and athletes. The study published in PLOS One investigates which sensory traits of a drink impact thirst and the amount of liquid people drink.

Findings from a study by Monell Center and collaborators could guide sensory approaches to increase fluid intake in populations at risk from dehydration, including the elderly, soldiers, and athletes.  The study published in PLOS One investigates which sensory traits of a drink impact thirst and the amount of liquid people drink. 

Breslin et al. recruited 98 healthy participants aged between 20 and 50 years old. To make them thirsty, the participants were told to stop drinking and consuming food 12 hours prior to intervention.  The team prepared a number of beverages (distilled water, acidified, carbonated, and astringent and sweet beverages) at either room temperature (20-22oC) or refrigerated temperature (6oC). 

At each session, in order to increase thirst further, the participants consumed a standardised breakfast, with participants rating their level of thirst at a comparable level of “strong”.  After a rest period, the participants were instructed to drink 400 mL of an experimental beverage in less than 5 minutes.  After a short period of rest, the participants were offered as much still, room temperature, unflavoured water to drink as they wanted.  The amounts drunk was used by the scientists as an indicated of how well the experimental beverage had quenched the participants thirst.  The scientists found that the cold water reduced thirst more effectively than the room temperature water. Overall a participant drank less from the jug after the cold carbonated water.  Acidification was found to not reduce thirst beyond that of cold water, stringency and sweetness sensation neither reduced nor increased thirst compared to the thirst quenching effect of room temperature beverage.

To further examine the role of cold-sensitive receptors in the mouth on thirst, the team investigated the effect of chemically-induced oral cold sensation using l-menthol.  I-menthol was used to stimulate and sensitise the sensory cold receptor TRPM8.  Breslin et al. tested the hypothesis that “a beverage illusorily perceived as cool, but physically room temperature, quenches thirst more effectively than a room temperature beverage that is perceived to be room temperature”.  The team used a similar protocol to the first experiment but used a pre-treatment of menthol before the consumption of the experimental drinks.  They report that “the perception of coldness, induced by either cold water (thermally) or by l-menthol (chemically), and the feeling of oral carbonation, strongly enhances the thirst quenching properties of a beverage in water-deprived humans (additional water intake after 400 ml experimental beverage was reduced by up to 50%).”

When the participants were asked to drink the experimental drinks blinded, and estimate the volume drunk, individual’s estimation of ingested volume is increased by around 22% by perceived oral cold and carbonation.  They note that this suggests that “cold and CO2 induced-irritation sensation are included in how we normally encode water in the mouth and how we estimate the quantity of volume swallowed.” 

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