An examination into the effect of genetic taste status and intensity of carbonation on swallowing and palatability in healthy young adults
Authors: Barry Eva , Regan Julie 
Published: June 2021

Background

Dysphagia is a highly prevalent condition and affects a wide range of cohorts. A common compensatory strategy to manage dysphagia is diet modification. However, this technique is often associated with poor patient quality of life and adverse long‐term effects. Carbonated liquids have shown promise as an alternative compensatory strategy for the management of dysphagia.

Aims

To examine the effect of genetic taste status and intensity of carbonation on swallowing and palatability in a healthy young adult population. To examine the palatability of carbonated liquids over time.

Methods & Procedures

A total of 35 healthy young adults were recruited for this prospective, quantitative cohort study. They each drank 150 ml of still water (SW), lightly carbonated water (LCW) and highly carbonated water (HCW). Swallow function, palatability and genetic taste status were assessed using the timed water swallow test, the hedonic general labelled magnitude scale and participant ratings of the bitterness of propylthiouracil strips, respectively. Participants were divided into groups of supertasters, moderate tasters and non‐tasters.

Outcomes & Results

A significant difference was found between SW and HCW on three tests of swallow function. Average time per swallow increased (p = 0.03), average swallow velocity decreased (p = 0.001) and average volume per swallow decreased (p = 0.017) on HCW compared with SW. HCW had a greater impact on swallow function than LCW. A significant mean difference in palatability ratings was found across intensity levels of carbonated fluids (p = 0.002), specifically between SW and HCW (p = 0.001). HCW was less palatable than SW. The palatability of carbonated liquids, investigated within a subgroup of five participants, did not decrease after a 24‐h period during which participants only drank carbonated liquids (p = 0.102). A significant difference was found between supertasters’ (n = 9) (mean = 13.33) and non‐tasters’ (n = 20) (mean = –24.5) palatability ratings of HCW (p = 0.03). Despite differences in swallow function between SW and HCW, no differences were detected between supertasters’ and non‐tasters’ swallow function on SW, LCW or HCW.

Conclusions & Implications

Carbonated liquids have the ability to alter swallow function in a healthy young adult population; however, liquids must be highly carbonated in order to have an effect. Additionally, highly carbonated liquids are less palatable than SW, but the palatability of carbonated liquids does not decrease over time. Furthermore, supertasters find HCW more palatable than non‐tasters. These findings suggest that carbonated liquids alter swallowing in a healthy population. Further research in a clinical population is needed to better understand the potential role of sensory stimulation as a dysphagia intervention.

What this paper adds

What is already known on the subject

Several studies have found that carbonated liquids have the ability to alter swallow function in both healthy and clinical populations. However, there is a lack of evidence around the optimum intensity of CO2 in carbonated liquids and the palatability of carbonated liquids as well as the palatability of carbonated fluids over time.

What this paper adds to existing knowledge

The findings from this study suggest that carbonated liquids can alter swallow function in a healthy young adult population, but liquids must be highly carbonated in order to have an effect. HCW is less palatable than SW, but the palatability of carbonated liquids does not decrease over time. Additionally, supertasters find HCW more palatable than non‐supertasters (non‐tasters).

What are the potential or actual clinical implications of this work?

The findings from this study suggest that carbonated liquids may be suitable for use as a sensory stimulation technique for people with dysphagia, as their palatability does not decrease over time; however, further research in a clinical population is needed in order to determine this. Additionally, intensity of stimulus is an important factor to consider during dysphagia evaluation to identify what intensity is required to optimize swallowing.