Differences in dynamic perception of salty taste intensity between young and older adults

Abstract

In super-aged societies, high salt intake substantially increases the risk of stroke and cardiovascular disease. Perceived low salty taste often prompts the addition of table salt to food. However, it remains unclear how older adults perceive the nature and intensity of salty taste in the mouth and brain. We compared the perceptions of salty taste intensities of older adults with those of young adults. Participants were 74 healthy adults: 31 older (age, 60–81 years [65.0 ± 5.5 SD]) and 43 young (age, 21–39 years [25.0 ± 3.6 SD]). Our research project comprises three sequential experiments. This article reports on the first two, which were (1) static and (2) dynamic sensory evaluations of taste perceptions in the mouth. Participants assessed the taste of 0.3 M and 0.5 M sodium chloride solutions in two types of sensory evaluations: (1) a cup tasting test, in which they sipped the solution from cups, spat it out, and rated static salty taste intensity, and (2) a time-intensity sensory evaluation, in which the solutions were delivered to participants’ tongues through a custom-made delivery system while they recorded dynamic taste intensities on a hand-held meter. Older adults perceived significantly lower taste intensities than young adults (p = 0.004 and p < 0.001 for 0.3 M and 0.5 M, respectively). Reaction timings for both solutions did not differ, but the slopes for both concentrations were significantly lower for older adults than for young adults (p < 0.001). Using a standardized system allowed us to evaluate and directly compare real-time feedback on taste intensities according to age. This study is the first to characterize the time-intensity profiles of salty taste intensity in older adults. Our findings show that older adults do not take longer to recognize a salty taste, but their perception of taste intensity slowly increases, and yet remains lower than that of young adults. This suggests that older adults should be aware of the tendency to add more salt to their food to compensate for their low perceptions of salty taste. We would like to suggest them to savor and chew sufficiently during eating to optimize the perceived salty taste. Furthermore, our results offer a reference for ordinary citizens’ taste-intensity perceptions; our standardized system could be usefully integrated into clinical follow-up examinations and treatments.

Differences in time–intensity sensory profiles of sweet taste intensity of glucose between older and young adults

“…We also recorded a decline in perceived sweet taste intensity during washing out. These data are not reported in this paper because the disappearance of the sweet sensation was not physiological but artificial ( Figure 3 ) ( 37 ).…”

“…The young adult group comprised 50 individuals [25 men, 25 women; age, 21–34 years (26.7 ± 3.3); BMI, 21.7 ± 3.0 kg/m 2 ] ( Table 1 ). This study included 16 older adults and 8 young adults included in a previous study ( 37 ). This study was a preliminary study, therefore, we set the number of participants per group tentatively.…”

“…The experiment started with the 0.6 M glucose solution (the lower concentration solution) and we then delivered the 1.5 M solution by the same method. Only one concentration within one session was used ( 37 ). A session consists of 10 pairs of glucose and distilled water delivery for 10 s each ( Figure 3 ).…”

“…The rotary dial consisted of a variable resistor and a 13 mm diameter knob. The scale on the dial corresponded to a taste intensity, ranging from 0 (no taste) to 10 (strongest taste imaginable) ( 37 , 40 ). A computer-controlled taste solution delivery system connected to the intra-oral device was synchronized with the time–intensity evaluation meter, and participants’ perceptions were monitored in real-time ( 37 , 40 ).…”

“…Previous studies have attempted to characterize the temporal aspects of taste perception in young adults, in terms of time–intensity evaluations ( 29 – 36 ). However, there have been no previous studies of time–intensity sensory evaluation of taste in older adults except for a study of salty taste, which showed that the perception of dynamic taste intensity in older adults increases slowly ( 37 ). Hence, we hypothesized that older adults perceive sweet taste intensity more slowly than young adults.…”