Objective: Reducing salt intake is a priority action for addressing the worldwide crisis of non-communicable diseases, and its various public approaches should be developed.
Educational background music (BGM) on reducing salt intake may nudge consumers at a canteen in choosing healthier meals or discretionary seasonings.
Design: The study design is a small-scale community trial that compared the control and the intervention periods.

Subjects: Subjects were unspecified consumers at a university canteen

Interventions: We displayed visual materials at a university canteen for 5 weeks (control period) and then broadcasted BGM for another 5 weeks (intervention period).

Measures of outcome: The consumption amount of discretionary seasonings and of soup in noodles and the consumption number of soup bowls and of noodles among the consumers, and the changes in the four above mentioned indices during both periods were compared by Mann-Whitney U test.
Results: Reductions in the consumption number of soup bowls and noodles were higher in the intervention period than those in the control period with statistical significance (median values: -7.5 and 5.4 per 100 rice consumers, p = 0.01; ratios to rice consumers, -0.02 and 0.10, p = 0.02, respectively).

Conclusion: Using a dietary education song on salt intake as BGM may be effective in influencing individuals toward healthier menu choices rather than seasoning behavior at a university's canteen.

Keywords: Behavior modification, BGM, Population approach, Reduced salt diet,Health education

Cardiovascular diseases (CVDs) and cancers are the leading causes of death globally [1]. Excessive salt or salted food intake is a major risk factor for both CVD (due to high blood pressure) and gastric cancer [2]. Reducing salt intake was indicated as the second priority action for addressing the crisis of non-communicable diseases (NCDs), including CVDs and cancer, in the UN High-Level Meeting on NCDs, 2011 [3]. Based on the report that the major sources of salt intake in the UK were processed foods, such as bread, cereals, and meat products (83% of the total salt intake) [4], the UK government and food industry collaborated to reduce the salt content in these foods. Eventually, they succeeded in reducing approximately 1 g salt/day in the average intake during 2000-2008 [5]. However, this strategy may be unsuitable for countries with different dietary patterns: for instance, bread and processed meat intakes were only 39 and 13 g/day in Japan, respectively [6], despite it being 87 and 62 g/day in the UK, respectively [7]. This approach by the UK government led to a reduction of only 1 g salt/day even in countries where the intake of these processed foods is relatively high; however, this approach may have little impact in countries where intake of these processed foods is lower. Therefore, an additional population approach to reduce salt intake should be considered for both the countries. Particularly, in countries, such as Japan, Korea, and China, where the primary sources of salt equivalent are soups and discretionary seasonings added to homemade foods or to cooked food already at the table (i.e., soy sauce and miso), public approaches raising the individuals' awareness on reducing salt intake may be effective [8].

A song regarding the appropriate amount of salt intake consisting of interesting sound and lyrics that encourage salt intake reduction was developed and provided as an educational tool by the government of Nara Prefecture [9]. The effect of background music (BGM) without words or of unspecified category on eating behavior was only examined consumption amount, such as the total energy intake [10-12], and the results were inconsistent. To the best of our knowledge, the effect of a music on dietary education consisted of interesting sound and lyrics about dietary modification has not yet been examined. Some large-scale approaches using mass media, such as television (TV) and radio, to promote salt intake reduction have been reported [13]. Using educational songs as BGM is potentially becoming more frequent and versatile approach in food purchasing and/or eating environments (e.g., canteens in workplaces and schools) to nudge consumers toward healthier choices.
Thus, we examined the effect of a dietary educational song regarding the appropriate amount of salt intake as BGM on individual behavioral modification at a university canteen. This was conducted by comparing the control and intervention periods.

We examined the effect of using a dietary educational song regarding the appropriate amount of salt intake as BGM on the users' behavioral modifications based on the sales record or leftover meals among unspecified consumer during the control and intervention periods in a university canteen in Japan. This intervention trial was approved by the Nara Women's University Institutional Review Board for epidemiological study (Approved on 16 June 2016). The study information was notified by means of posters, instead of personalized informed consent, at the canteen entrance because the assemblage of the subjects consisted of unspecified customers at the canteen.
Lunch time during weekdays (5 weeks) was set as the experimental period from June 2016 to August 2016 (control period) and from November 2016 to December 2016 (intervention period) (Figure 1). With regard to the possible replacement of the canteen users by admission and graduation and on comparability caused by different menu styles between different facilities, we scheduled control and intervention periods in different seasons.
During the control period, we displayed posters and tabletop notes, and distributed leaflets, illustrating the Japanese Food Guide Spinning Top [14], as conventional visual manners, at the canteen. Conversely, during the intervention period, we additionally broadcasted the dietary educational song as BGM at the entrance of the canteen.

We evaluated the following four indices in the canteen per each day of the week during the 5 weekdays before the start and end of the periods: (1) consumption amount of discretionary seasonings added per consumer, (2) consumption amount of soup in noodles (%) per canteen, (3) consumption number of soup bowls, and (4) consumption number of noodles per capita.
First, to determine the consumption amount of seasonings at the table (per 100 consumers) as a discretionary seasoning behavior, bottled soy sauce, ponzu (sour-tasting soy sauce), sauce (thickened Worcestershire sauce), and dressings were weighed before and after lunchtime. The differences were considered as the gross consumption of the day of each seasoning. These gross consumptions were divided by the number of canteen consumers during lunchtime based on the point-of-sale (POS) system. Second, the consumption amount of soup in noodles (%) was determined by the difference between the total amount of soup provided and total amount of leftover soup in the canteen.
We classified the noodle menu into the following three types according to the recipe and bowl size for eating: Japanese, curry, and Chinese noodles. To determine the amount of leftover soup, we distributed measurement papers to the consumers who ordered noodles. Thereafter, either the consumers themselves or we measured the depths of leftover soups (in mm), and we then collected the measurement papers. We developed formulas to estimate the amount (ml) of leftover soup by depth (mm) measured according to the three aforementioned menu types. We poured water into the bowls and measured its amount (ml) and depth (mm) of the water in the bowls and then performed quadratic regression. Consequently, we obtained the following formulas: (1) amount of leftover soup in Japanese noodles (ml) = 0.121 x [depth (mm)]2 + 5.244 x depth (mm); (2) amount of leftover soup in curry noodles (ml) = 0.095 x [depth (mm)]2 + 3.986 x depth (mm); and (3) amount of leftover soup in Chinese noodles (ml) = 0.161 x [depth (mm)]2 + 6.778 x depth (mm) (Figure 2). The amounts of leftover soups were summed per each three menu types. We did not measure the leftover amount of cold Japanese noodles due to the different forms of bowls used. Third, the consumption number of soup bowls (salty taste) was obtained from the POS system. To evaluate the behavior on the discretional selection of soup by the consumers, the consumption number of lunch set with miso soup was excluded from both the number of soup bowls and the total number of consumers. Then consumption number of soup bowls per 100 consumers of the day was calculated. Additionally, to evaluate the proportion of consumers who selected soup bowls with rice and to adjust the difference of lunch set provided (rice, main dish, some vegetable dishs, and soup) between the control and intervention periods, the consumption number of soup bowls was divided by the number of rice (including bowl rice [bowl of rice with food on top] and excluding curry rice) sold. Fourth, the consumption number of noodles, including cold Japanese noodles, was obtained from the data in the POS system. We determined the consumption number of noodles per 100 consumers of the day. The ratio of the consumption number of noodles to that of rice was determined to evaluate the influence on the consumers' menu selection for "staple food" (grain). In other words, we evaluated whether the consumers modified their menu choice from foods with higher salt content (noodles) to foods with less salt content (rice) as their staple food.

We compared the changes between the control and intervention periods. In this study, we assessed the changes in salt intake on a mass level, rather than on an individual level, in the said canteen during weekdays (Monday-Friday). In both the control and intervention periods, changes were calculated between each day's control and intervention periods. The differences in the changes between the control (n = 5 days) and intervention periods (n = 5 days) were analyzed by Mann- Whitney U test. We used the IBM SPSS Statistics 21.0 (IBM Japan, Ltd.) for all statistical analyses. The significance level was set at <5% (two-sided test).

We examined the effect of using the dietary education song regarding the appropriate amount of salt intake as BGM in a university canteen by comparing the consumption amount of discretionary seasonings and noodle soups or choices of salty tasting menu between the intervention and control periods.
The reductions in the consumption amount of discretionary seasonings and soups in noodles were not statistically larger in the intervention period than those in the control period. In contrast, the consumption numbers of soup bowl with rice and of noodles
as the staple diet were decreased in the intervention period than those in the control period, and these were considered statistically significant. These results suggest that using the dietary education song as BGM at a canteen influences the individual's choice on salty tasting menu rather than the salt intake behaviors at the table. Furthermore, as a potential mechanism of the influences for groups, the BGM might work as a trigger of the group dynamics toward healthier choices, although it is unclear whether the effects can be explained by the synchronization of brain activity and/or being on the same wavelength [15].
To our knowledge, this is the first study that examined the effect of using a dietary education song regarding salt intake as BGM. Some reports on nationwide campaigns focused on the reducing salt intake and increasing the awareness using mass media (TV, radio, newspapers, and billboards) by the UK and Ireland governments as a large-scale population approach are available [5, 16-18]. However, such approach may potentially lack versatility or regionality and continuity. An intervention using a song regarding the appropriate amount of salt intake is available on a smaller scale such as in municipalities and canteens in workplaces or schools. This type of intervention can be advantageous to reduce salt intake. Using educational songs as BGM is potentially becoming a more versatile approach in the food environment, including canteens in workplaces and schools.
The results of our study demonstrate that using a dietary education song regarding the appropriate amount of salt intake as BGM at a canteen influences the consumers to avoid noodles and soup bowls on their menu choices. This suggests that such measures will help the population in reducing salt intake in the Asian diet culture because soups such as miso soup and noodle soup comprise relatively major diet sources for Asian people [19-20]. In Japan, miso soup and noodle soup contribute to 16.4% of salt intake [19]. In Korea, people consume an excessive amount of salt from soup or stew [20]. Therefore, the food choices of canteen consumers or supermarket shoppers can be nudged toward healthier meal selections [21,22] using educational song as BGM based on the behavioral and economic theories of decision-making "nudge" [23].

Using a dietary education song regarding the appropriate amount of salt intake as BGM is effective in influencing the individuals regarding their menu choice rather than the behavior of discretional seasoning at the table in a university canteen.

RT conceptualized, supervised, and administrated the project. SM and YT performed formal analysis. SM wrote the first draft. YS, HN, and RT performed investigation. All authors reviewed and commented on subsequent drafts of manuscript.

The authors are grateful to the Nara prefectural office and Nara Women's University co-operative association's cafeteria. We also appreciate the assistance from the members of the public health nutrition laboratory, Nara Women's University. This research received JSPS KAKENHI Grant Numbers 19K20146. The authors declare no conflict of interest.

1. He FJ, Macgregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens. 2009;23(6):363-384.
2. Takachi R, Inoue M, Shimazu T, Sasazuki S, Ishihara J,et al. Consumption of sodium and salted foods in relation to cancer and cardiovascular disease: the Japan Public Health Center-based Prospective Study. Am J Clin Nutr. 2010;91(2):456-464.
3. Beaglehole R, Bonita R, Horton R,Adams C, Alleyne G, et al. Priority actions for the non-communicable disease crisis. Lancet.
2011;377(9775):1438-1447.
4. Science Advisory Committee on Nutrition. Salt and Health. Public Health England. 2003.
5. Wyness LA, Butriss JL, Stanner SA. Reducing the population's sodium intake: the UK Food Standards Agency's salt reduction programme. Public Health Nutr. 2012; 15(2):254-261.
6. Ministry of Health, Labor and Welfare. National Health and Nutrition Survey in Japan (2016) [in Japanese]. 2017.
7. Public Health England and the Food Standars Agency. National Diet and Nutrition Survey Results from Years 1, 2, 3 and 4 (combined) fo the Rolling Programme (2008/2009 - 2011/2012). 2014.
8. Brown IJ, Tzoulaki I, Candeias V, Elliott P. Salt intakes around the world: implications for public health. Int J Epidemiol. 2009;38(3):791-813.
9. Nara Prefecture. Tools for reduced salt [in Japanese]. 2015.

10. Peneau S, Mekhmoukh A, Chapelot D, et al. Influence of environmental factors on food intake and choice of beverage during meals in teenagers:a laboratory study. Br J Nutr. 2009;102(12):1854-1859.
11. Stroebele N, De Castro JM. Listening to music while eating is related to increases in people's food intake and meal duration. Appetite. 2006;47(3):285-289.
12. Mamalaki E, Zachari K, Karfopoulou E, Zervas E, Yannakoulia M. Presence of music while eating: Effects on energy intake, eating rate and appetite sensations. Physiol Behav. 2017;168:31-33.
13. Trieu K, Mcmahon E, Santos JA, et al. Review of behaviour change interventions to reduce population salt intake. Int J Behav Nutr Phys Act. 2017;14(1):17.
14. Yoshiike N, Hayashi F, Takemi Y, Mizoguchi K, Seino F. A new food guide in Japan: the Japanese food guide Spinning Top. Nutr Rev. 2007;65(4):149-154.
15. Goede N, Engelbregt H. Op dezelfde golflengte [in Netherlandish]. GGZ Vaktijdschrift.2018;1(2):6-8.
16. He FJ, Brinsden HC, Macgregor GA. Salt reduction in the United Kingdom: a successful experiment in public health. J Hum Hypertens. 2014;28(6):345-352.
17. Millett C, Laverty AA, Stylianou N, Bibbins-Domingo K, Pape UJ. Impacts of a national strategy to reduce population salt intake in England: serial cross sectional study. PLoS One. 2012;7(1):e29836.
18. Safefood. Safefood Advertising and Corporate image tracking research wave 7.2006.
19. Anderson CA, Appel LJ, Okuda N, et al. Dietary sources of sodium in China, Japan, the United Kingdom, and the United States, women and men aged 40 to 59 years: the INTERMAP study. J Am Diet Assoc. 2010;110(5):736-745.
20. Kim GH, Lee HM. Frequent consumption of certain fast foods may be associated with an enhanced preference for salt taste. J Hum Nutr Diet. 2009;22(5):475-480.
21. Friis R, Skov LR, Olsen A, et al. Comparison of three nudge interventions (priming, default option, and perceived variety) to promote vegetable consumption in a self-service buffet setting. PLoS One. 2017;12(5):e0176028.
22. Quigley M. Nudging for health: on public policy and designing choice architecture. Med Law Rev. 2013;21(4):588-621.
23. Thaler R, Sunstein C. Nudge: Improving Decisions about Health, Wealth and Happiness. Yale University Press.2008.
24. El Ansari W, Stock C, John J, et al. Health promoting behaviours and lifestyle characteristics of students at seven universities in the UK. Cent Eur J Public Health. 2011;19(4):197-204.
25. Tanton J, Dodd LJ, Woodfield L, Mabhala M. Eating Behaviours of British University Students: A Cluster Analysis on a Neglected Issue. Adv Prev Med.2015:639239.