Validation of preferred salt concentration in soup based on a randomized blinded experiment in multiple regions in Japan—influence of umami (l-glutamate) on saltiness and palatability of low-salt solutions

Abstract

Sodium reduction is an important public health goal. Individual and population approaches are necessary for reducing the sodium content of processed foods and meals. The aim of the present study is to affirm the effect of monosodium L-glutamate (MSG), an umami substance, on the saltiness or palatability of low-salt solutions and to explore the preferred salt concentration in soup. Five hundred and eighty-four healthy participants from nineteen regions in Japan tasted 0.3, 0.6, and 0.9% NaCl solutions with or without 0.3% MSG. Evaluations of saltiness and palatability for each solution were conducted using a visual analog scale in a double-blinded randomized manner. Saltiness gradually increased depending on the concentration of NaCl. The saltiness of the 0.3% NaCl solution with MSG was rated significantly higher than that without MSG. The palatability ratings were higher for the solutions with MSG than for those without MSG for all NaCl concentrations. In particular, the palatability rating of the 0.3% NaCl solution with MSG was twice as high as that without MSG and was significantly higher than that of the other five test solutions. Furthermore, these results were observed to be approximately the same, irrespective of sex, age, region, etc. Salt reduction is believed to result in a loss of palatability. However, our results suggest that umami can compensate for the loss of palatability caused by salt reduction and that the addition of an appropriate amount of an umami substance can facilitate salt reduction from 0.9 to 0.3% without sacrificing palatability.

Umami and salt reduction

“…In the present study [3], MSG appeared to elevate palatability at three different salt concentrations in both students and health seminar participants in all areas of Japan where the study was done ( Supplementary Figs. 1-B and 2-B) [3].…”

“…In the present study [3], MSG appeared to elevate palatability at three different salt concentrations in both students and health seminar participants in all areas of Japan where the study was done ( Supplementary Figs. 1-B and 2-B) [3]. On the other hand, an MSG-induced increase in saltiness was observed only for the 0.3% salt solution but not for the 0.6 or 0.9% salt solutions (Supplementary Figs.…”

“…On the other hand, an MSG-induced increase in saltiness was observed only for the 0.3% salt solution but not for the 0.6 or 0.9% salt solutions (Supplementary Figs. 1-A and 2-A) [3]. This effect of MSG was lower for the health seminar participants than for the students.…”

“…Tasting umami flavors may be a unique sensory function to ameliorate the palatability of foods. Hayabuchi et al demonstrated that an umami substance, monosodium L-glutamate (MSG), ameliorated the decrease in palatability caused by salt reduction in students from eight universities and adult attendees of eleven health seminars in Japan (n = 584) [3]. The study participants were within a wide range of ages (19 to >70 years old), and examinations were performed in Tohoku (the northern area of Japan) to Kyushu (the southern area of Japan).…”

“…On the other hand, European populations utilize umami from tomatoes, cheese, and ham. Thus, umami helps salt reduction worldwide; There are many reports from investigators around the world suggesting that the addition of umami into food allows for salt reduction, as mentioned in the discussion by Hayabuchi et al [3]. In 2010, the Institute of Medicine of the National Academies (IOM) mentioned in their booklet Strategies to reduce sodium intake in the United States that "It is possible to replace some of the salt in foods with other taste or flavor compounds or through other flavor strategies or techniques.…”