Barriers, Enablers, and Perceptions on Dietary Salt Reduction in the Out-of-Home Sectors: A Scoping Review

In this review, we have investigated the perceptions, barriers, and enabling factors that were responsible for a dietary salt reduction in the out-of-home sectors. For this purpose, we examined different knowledge databases such as Google Scholar, Ebscohost, MEDLINE (PubMed), Ovid, and Cochrane Library for research articles from September to December 2020. The inclusion criteria for the research articles were that they had to be published in English and had to be a qualitative or quantitative study that was conducted after 2010. These studies also had to report the various enablers, barriers, and perceptions regarding salt reduction in the out-of-home sectors. After implementing the inclusion criteria, we successfully screened a total of 440 studies, out of which 65 articles fulfilled all the criteria. The perceived barriers that hindered salt reduction among the out-of-home sectors included lack of menu and food variabilities, loss of sales due to salt reduction, lack of technical skills for implementing the salt reduction processes for cooking or reformulation, and an absence of environmental and systemic support for reducing the salt concentration. Furthermore, the enablers for salt reduction included the intervention programs, easy accessibility to salt substitutes, salt intake measurement, educational availability, and a gradual reduction in the salt levels. With regards to the behavior or perceptions, the effect of organizational and individual characteristics on their salt intake were reported. The majority of the people were not aware of their salt intake or the effect of salt on their health. These people also believed that low salt food was recognized as tasteless. In conclusion, the enablers, barriers, and perceptions regarding salt reduction in the out-of-home sectors were multifaceted. Therefore, for the implementation of the strategies, policies, and initiatives for addressing the barriers, the policymakers need to encourage a multisectoral collaboration for reducing the salt intake in the population.


Introduction
A majority of the countries, worldwide, have undertaken steps to decrease the salt intake in their population. Most of the salt reduction strategies such as legislation, reformulation, and salt reduction intervention programmes were suggested by the industries as well as governmental and non-governmental organizations [1,2]. Despite the probable health benefits of a low salt intake, very few researchers have investigated the implementation of the salt reduction intervention for achieving a sustained reduction of salt intake among the Low-and Middle-Income Countries (LMICs) [3,4]. It was noted that translational research could help in determining the available intervention steps which were effective and suitable for various contexts. In an earlier study, the researchers concluded that based on the moderate quality of the evidence, the population-level interventions could improve the salt-related behaviour of the people [5].
A systematic review conducted by Cappuccio et al. (2015) indicated that some of the successful policies included comprehensiveness, which involved health education, population monitoring, and reformulation for decreasing the salt concentration included in the processed foods (responsible for ≥75% of the daily salt intake) [6]. These populationbased salt reduction policies were rapid, equitable, powerful, and enabled cost saving.
The United Kingdom developed an excellent and popular national salt reduction strategy in 2003. These policies included three major factors, i.e., improved nutrition labelling, consumer awareness campaigns, and a government-backed salt reduction model which set low salt targets for more than 85 different food categories that had to be achieved by the food manufacturers within a specified time frame [7]. This resulted in a 15% decrease in the salt intake within the population in the United Kingdom (from 9.5 to 8.1 g/day, in the period ranging from 2001 to 2011) [7]. Very few studies have shown that salt intake was influenced by income. Azizan et al. (2020) carried out an intervention study and noted that dietary modification could improve the nutritional intake such as the salt intake and the biochemical profile of the low-income urban population suffering from hypertension in Malaysia [8].
The out-of-home sector consists of the outlets which serve foods and drinks for immediate consumption or take away. This sector includes formal and informal sections. A formal out-of-home sector that includes the licensed and registered cafes, restaurants, school/work canteens, fast food outlets, takeaways, food delivery services or hotel restaurants. On the other hand, the informal out-of-home sector includes street hawkers, food vendors, and food delivery services [9].
Commonly, many people worldwide, are choosing to dine outside their homes [10,11]. A survey was carried out in the USA, which showed that ≥50% of the adults eat out more than 3 times per week, while 35% of the adults eat fast food meals at least 2 times every week [12]. In 2012, another study was conducted in China, where the researchers determined the relationship between the nutritional status of the residents and the onset of chronic diseases. The researchers noted that 35.5% of the residents, aged above 6 years preferred dining out. Out of these, 42.2% were urban residents, while 28.5% of the people were rural residents [13]. The home-cooked meals were regarded as healthier compared to those purchased from out-of-home places [14,15]. Furthermore, the out-of-home meals contained higher levels of salt, added sugar and saturated fats, while they were also low in vitamins, fiber, and minerals compared to the home-cooked meals [16]. The research question for this review paper is "What are the barriers, enablers and perceptions on dietary salt reduction in the out-of-home sectors?" Hence, this review was carried out for identifying the different barriers, motivators, and perceptions of the people regarding the reduction of dietary salt levels in out-of-home meals. This review would also help in identifying the different strategies that can be used for salt levels reduction.

Materials and Methods
In this study, the researchers have adopted the framework proposed by Arksey and O'Malley (2005) for scoping different reviews [17], along with the enhanced and adapted methodologies proposed by Levac et al. (2010) and Daudt et al. (2013) [18,19]. Based on all these frameworks, the researchers implemented five stages, such as (i) Identifying research questions; (ii) Determining important studies; (iii) Selection of the studies; (iv) Charting data; and (v) Collating, summarizing, and presenting all the results. This framework is the most commonly used framework in the scoping review. The researchers did not use ethical registration since this was a scoping review.

Identification of the Relevant Study
A search strategy was developed collectively. Regular discussions and meetings were conducted for determining the significance of all citations and resolving disagreements. The first author (V.M.) primarily conducted the search and two co-authors (Y.X.Y. and S.N.S.) independently searched using the same keywords. Consolidation of articles to be included in the review was done among these three authors. Some inclusion criteria were set before selecting the citations. These criteria stated that the study must be published in the English language, must be peer-reviewed or grey literature, and must be published between 1 January 2010 and 31 December 2020. These reports must also describe and highlight the enablers, barriers, and perceptions related to the sodium or salt reduction amongst the people, along with the steps undertaken by the policymakers or out-of-home sectors for implementing these steps. On the other hand, the studies that were not original editorials, book chapters, research articles, reviews, opinions, and commentaries or did not include new information and knowledge were not included in this review. Moreover, the studies that presented only summaries of earlier reports were not included in the review.
Perceived barriers are defined as a person's estimation of the level of challenge of social, personal, environmental, and economic obstacles to a specified behavior or their desired goal status on that behavior [20]. While, enablers are defined as the one that enables another to achieve an end in salt reduction strategies [3].
The search strategy used in this study was a combination of various keywords such as (Barriers OR enablers OR perceptions OR facilitators) AND (salt OR sodium reduction)) AND (out-of-home OR street OR restaurants OR cafeteria OR work place OR food industries). The synonyms and keywords generated after using the search terms are presented in Table 1. The search strategy was implemented on different databases such as Google Scholar, Ebscohost, MEDLINE (PubMed), Ovid, and Cochrane Library. After using the inclusion and exclusion criteria, the search yielded 440 studies, out of which 65 articles (three qualitative and 62 quantitative studies) fulfilled all the criteria. Figure 1 presents the flow chart diagram implemented in the study.  Table 2 presents a summary of the study characteristics included in the review. Thereafter, the researchers extracted and tabulated each abstract and full text of the final 65 studies included after the final analysis, for highlighting the year, survey, country, study design, participants, methodologies, results, and conclusions (Supplementary Materials Table S1). We analyzed every study for categorizing the studies into three major themes, i.e., barriers, enablers, and perceptions.   Table 2 presents a summary of the study characteristics included in the review. Thereafter, the researchers extracted and tabulated each abstract and full text of the final 65 studies included after the final analysis, for highlighting the year, survey, country, study design, participants, methodologies, results, and conclusions (Supplementary Materials Table S1). We analyzed every study for categorizing the studies into three major themes, i.e., barriers, enablers, and perceptions. The central and state governments (n = 4); the India Office and the South East Asia Regional Office of the World Health Organization (n = 5); the Indian Council of Medical Research (n = 2); the World Bank (n = 1); food manufacturers (n = 6); the academia (n = 10); the National Institute of Nutrition (NIN) (n = 3); the civil society (n = 4); community members (n = 7) from the urban and rural areas [22] Table 3 summarizes the findings related to barriers, enablers, and perceptions of dietary salt reduction in the out-of-home sectors.    The majority (82%) was willing to reduce sodium in restaurant foods under the support of local government and they desired the promotion of participating restaurants and education on cooking skills to reduce sodium [62] Note: UK: United Kingdom; USA: United States of America.

Barriers of Dietary Salt Reduction in the Out-of-Home Sectors
The findings for the barriers which prevented salt reduction in the out-of-home sectors included the lack of menu and food variabilities, lack of technical skills for cooking, profit loss due to salt-reduced foods, lack of technical expertise for reformulation, and other factors as listed in Table 3.

Enablers of Dietary Salt Reduction in the Out-of-Home Sectors
Enablers are described as factors that help in the implementation of salt reduction programmes, strategies, initiatives, and interventions for various out-of-home sectors. Enabling factors that encouraged a salt reduction in the out-of-home sectors included the salt reduction intervention program, food analysis studies, salt substitute accessibility, gradual reduction of salt approach, training availability, and other factors which were categorized separately as listed in Table 3.

Perceptions of Dietary Salt Intake in the Out-of-Home Sectors
The perceptions of people on salt intake in out-of-home sectors are shown in Table 3. These included the negative effects of a high salt diet, low salt foods recognized as tasteless, and individual or organizational characteristics effects in salt reduction.

Discussion
The out-of-home sectors that have been considered in this review include catering operators, food industries, school children, workplace organizations, and food industries. Food industries worked hand-in-hand with the policymakers and implemented interventions for decreasing the total salt content. The majority of the interventions which targeted the foodservice settings and work places were implemented in the USA, South Korea, and China [21,31,63].

Dietary Salt Intake and Sources
The studies carried out in the USA showed that salt was added to the diet from different packaged/non-packaged foods or foods sourced from out-of-home settings. This was responsible for a total of 67-70% of the salt intake among the population [64,65]. Similarly, studies conducted in the European Union indicated that the people had a higher salt intake, wherein 75-80% of the salt intake was due to the consumption of processed foods, 10-15% of the salt was added during the cooking process or at the table, while 5-10% of the salt was naturally present in different food items. However, in developing and LMIC countries, the salt that was used for seasoning played a vital role [29,83]. A recent study showed that the intake of salt was increasing amongst the Chinese population [78]. A majority of the processed foods that were available in the Chinese local supermarkets were high in salt content [84].
This scoping review noted that a majority of the countries such as the UK, USA, Australia, European countries, South Korea, and Brazil have set a few national voluntary targets [45,48]. This was implemented after many reformulation efforts were carried out in the food products such as meat, dairy products, bread, and soups [29,46,58]. This was considered a very effective intervention as it helped in averting 0.7-1.9 million deaths in 10 years using a modelling approach, as proposed by Coxson et al. (2013) [82]. Moreover, mandatory salt reduction targets using legislation were achieved in South Africa for many food products [28].

Barriers for Dietary Salt Reduction
A lack of availability of low salt foods, lesser food choices or menu variability and incomprehensive salt data were regarded as major barriers that affected the out-of-home sectors in this review. These issues were attributed to a lack of technical skills for reformulation and cooking low salt foods [26]. An absence of food analysis techniques for measuring the salt concentration in the foods was also an issue.
Issues related to the lack of technical skills in preparing or producing low salt foods have to be resolved as they can lead to food safety problems, concerns regarding consumer acceptance, higher costs, and complications arising due to the use of various sodium alternatives. This can be a factor that could demotivate the food manufacturers in European countries [29]. In addition, several environmental factors such as pressure for maintaining profit margins and fear of decreased sales from the industrial sectors act as barriers that prevent the production of low salt foods [21,22,47]. Many of the barriers listed in this scoping review are dependent on capacity building and can easily be eliminated through proper training, intervention or education as highlighted in the Enablers findings.

Enablers for Dietary Salt Reduction
The effective intervention strategies include product substitutions [25], recipe modification [40], social marketing approach [39], comparing the salt concentration in different pre-packaged foods based on the available data such as sales-weighted sodium concentration and sodium data presented on the Nutrition Facts panel provided in the restaurants and point of purchase, offering low salt foods and encouraging the consumers to buy low sodium food products.
Salt substitutes that are used for reformulating the food products such as potassium chloride can be used for replacing the sodium chloride salts in various products [33,79]. Additionally, potassium citrate can be used for replacing salt in different types of bread [34] or herbs can be used as a salt substitute while cooking foods at home [33]. Salt substitutes such as potassium chloride could reduce dietary sodium intake and cause an increase in dietary potassium results in the decreased incidence of hypertension [79]. Reformulating food products to lower sodium levels using potassium chloride may actually result in positive health effects in the general population [79]. The limited availability of different low salt food products in the supermarkets, cafeteria, work-places, vending machines, and kiosks is attributed to the inability of the food manufacturing companies in reformulating their food products [48] or a lack of technical skills by the workers and chefs. Hence, the policymakers need to develop policies to reformulate the foods using various salt substitutes [41] and provide technical training to the different personnel with regards to food preparation, food procurement or marketing [63]. In one wholesale survey study, the researchers noted that when people were offered nine types of low salt bread that were prepared using potassium citrate, they accepted the products and did not voice any complaints regarding the flavor changes. They further stated that the respondents were unaware of salt substitution and reduction [34]. This study indicated that it is possible to reduce the salt concentration in foods using appropriate salt substitutes, without altering the taste of the food.
For ensuring salt reduction, the policymakers have to carry out a food analysis study and update their databases to provide information related to the salt content in the packed foods or food acquired from out-of-home sectors to monitor and compare the salt targets and provide better food labels [74]. The salt concentrations can be measured after a 24 h urine analysis along with the blood pressure after 6 months of three educational interventions among 155 of 10-12 years old school children. This helps in determining if the salt reduction intervention is effective or not [33]. It is important to identify the partners having a shared experience and common objectives and who aim for a sustainable salt reduction [40].
Effective legislation is one of the salt reduction strategies that has been implemented in many countries such as South Africa, Argentina, Belgium, Bulgaria, Netherlands, Portugal, and Paraguay [23,75,[85][86][87]. For instance, South Africa and Argentina have set the maximum total sodium levels for 13 and 18 categories of food products, respectively that started in 2013 [85,88]. The other countries have also implemented the legislation on salt reduction through the regulation by setting the maximum level of sodium content in food products such as breads, cheese, meat, and poultry [75,86,87].
Appropriate training must be provided to the staff for food preparation, food procurement, and marketing [63]. It helped the employees improve their skills and learn new techniques for preparing low salt food such as in the Korean catering firms [21]. The staff should also be trained to improve their knowledge for reducing salt intake [43].
Other enabling factors which helped in reducing the salt intake included the maintenance of customer demands, implementation of effective strategies, and support. Monitoring and establishing a partnership between the state, local, and national health organizations is necessary [48]. The psychological characteristics of the stakeholders and environmental factors also play a vital role in decreasing salt intake. A supportive social setting helps in improving the dietary habits of the people who eat foods with a higher salt concentration [62].

Perceptions on Dietary Salt Reduction
A study by Ma et al. (2014) indicated that very few people in the USA are aware of the dangers of taking high salt-content foods and display a lack of knowledge regarding the salt content in the packaged food products [63]. This issue can be resolved by implementing education-based intervention strategies such as community awareness campaigns, schoolbased education, and media campaign regarding salt reduction [57].
Furthermore, individual and organizational characteristics play a vital role in salt intake. Mallia et al. (2012) conducted a survey that showed that 90% of the respondents added salt to their dishes for improving the flavor and taste of the foods [49]. With regards to gender, many of the women add salt to the foods during cooking compared to the men who add more salt to their food on the table. Moreover, many women believed that salt added during cooking was the major source of salt in their diet. The study indicated that the Greek adults aged from 25 to 34, 35 to 44, and 45 to 54 years had a better knowledge regarding the harmful effects of salt on their health in comparison to respondents above 55 years of age [66]. With regards to individual knowledge, one-third of the Australian adults (32%) stated that they added salt to their plates on the table. Seventy three percent of the respondents stated that they had seen or heard the salt reduction messages [55]. Some of the factors which contributed to a higher salt intake included age and gender (which could not be modified), in addition to knowledge, attitude, and practices followed by the individuals that can be modified and improved by education [7,89,90].
Very few studies were conducted in the LMICs, particularly in the South-East Asian regions. The cost-effectiveness of implementing salt reduction strategies in these countries was not reported. Hence, a detailed and comprehensive study needs to be carried out in the future. A majority of the barriers, enablers, and perceptions of the individuals highlighted in this scoping review can help the governments and policymakers in the LMIC regions for developing, implementing or monitoring the strategies and policies for reducing the salt intake among the people.

Conclusions
This review defined the various barriers affecting the implementation of salt reduction strategies, which were (1) Lack of menu and food variabilities, (2) Lack of technical skills for cooking with lower salt, (3) Profit loss due to loss of sales, and (4) Lack of technical expertise for reformulation. The enablers themes are (1) Salt reduction intervention, (2) Food analysis studies and salt intake measurement, (3) Salt substitute accessibility, and (4) Gradual reduction of salt approach and Training availability. The perceptions themes are (1) Individual or organizational characteristics effects on salt intake, (2) Negative effects of high salt diet, and (3) Low salt food was recognized as tasteless. It was seen that the barriers, enablers, and perceptions regarding the dietary salt reduction in the out-of-home sectors were multifaceted. It is important to implement strategies, policies, and initiatives for addressing the barriers. For this purpose, a multisectoral collaboration from different stakeholders such as policymakers, food industries, catering operators, and food vendors is necessary to reduce the salt intake in the out-of-home sectors.