Historically, salt has provided a great service to humanity, facilitating the development of agriculture and conservation techniques (4), taxation and exchanges of goods and services (4–6), and the increase of taste values in processed foods (6). Salt and dietary sodium enhance food taste, flavor, texture, mouthfeel, and palatability; it reduces bacterial growth in meats, cheeses, and other animal products, and it also enhances hedonic attraction to vegetables among children (5, 7). Finally, iodized salt has proved to be a successful tool for iodine deficiency prevention: due to its ubiquitous use, women and infants who use iodized salt display sufficient iodine levels (8–11). Similar logic was applied to salt fluoridation (12, 13).

An excessive intake of dietary sodium and salt, however, constitutes a major challenge to public health globally, particularly touching low-and middle-income countries (3, 14–16). Analyzing the ‘Global Burden of Disease, Injuries, and Risk Factor study’ (GBD) 2013 and 2017 to identify emerging public health challenges, GBD 2013 Risk Factors Collaborators observed that diets high in sodium contribute to the risk factors for multiple noncommunicable diseases, with visible increase from 2011 onwards (17), mostly in Asian countries (18). According to the authors, the minimum risk of sodium intake approaches 5 g per day, which is also the amount recommended by the WHO. However, the current mean of salt intake in the WHO member states is almost twice the recommended value despite the agreement to reduce the intake of salt by 30% by 2025 (1, 6, 19–21). Salt overconsumption is a significant factor increasing blood pressure and leading to cardiovascular and kidney disease (6, 22). It is one of the top two dietary risk factors contributing to 1.65 million cardiovascular-related deaths each year (17, 18, 23, 24). Mostly touched by hypertension are low-and middle-income countries (25), where awareness of the dangers of salt and sodium remains low (14, 15, 26, 27).

This ambivalent position of salt in human diet (both as a necessity element and as a danger if consumed in large amounts) makes it challenging to develop effective guidelines for public health interventions. The intake of dietary sodium derives from three sources: [1] processed or manufactured foods (e.g., bread, soup, snacks, and restaurant meals); [2] salt contained in foods (e.g., celery, artichoke); and [3] discretionary salt (DS) added by consumers during cooking, food preparation and/or at the table (28). Most of the research data on salt and sodium overconsumption today concerns sodium and salt in products and processed foods (5, 29) since they are major contributors of sodium intake, particularly breads, processed meats, and sauces (30). However, these data must be accompanied by an understanding of exact consumer practices of sodium intake in order to provide a basis for effective sodium reduction campaigns. For example, Blanco-Metzler et al. (31) qualitative exploratory study in Costa Rica, where cardiovascular diseases have been the leading cause of deaths, demonstrates that most of the sodium intake daily came from domestic consumption. The authors relate this phenomenon to the beliefs that food cannot be consumed without salt, to the habits of salting generously, and the lack of awareness that processed foods already contain sodium (ibidem).

The midpoint of the WHO public health campaign for the decrease of dietary sodium consumption shows that low-income countries are still far from reaching an international goal (3, 32). Building on this point, we propose to revisit existing approaches to reducing salt consumption from an eater-oriented perspective, taking into account social, cultural, nutritional, interactional, and hedonic influences. Our argument also follows Kwong et al.’s warning that existing methods of measuring daily salt intake (24 h urinary collections, spot urine collection, dietary recall, food frequency questionnaires (FFQs), dietary records, household budget surveys) do not produce consistent results (3). By conducting a scoping review of existing studies at the crossroads of salt consumption and public health, we categorize studies from nutrition, health management, clinics, cultural anthropology, and sociology, thus building an interdisciplinary documentary base of sodium consumption factors. This documentary base proposes an eater-oriented framework to categorize data on salt overconsumption, linking nutritional knowledge with social sciences to facilitate heterogeneous and eater-oriented knowledge and evidence production. We suggest that databases built though this framework and grounded into the context of a particular country may provide fruitful evidence for effective public health guidelines for dietary sodium reduction in the second half of the WHO 2013 campaign aiming to decrease the amount of sodium consumed by 30% by 2025.

According to Durazzo and Lucarini, a better understanding of the frontier between diet and health requires new databases, especially in the perspective of factors contributing to chronic illnesses (33). This need is dictated, among others, by the search of adequate food policies, by promotion of nutritional knowledge among the consumers, and by the proven effects of balanced diet on the general health level. In this frame of reference, a collection of articles on the topic of databases and nutrition was published in Frontiers in March 2022 under the direction of Durazzo and Lucarini. This collection has presented new types of databases, dealing not only with nutritional components (for example, systematizing the types of low-or no-calorie sweeteners in products and beverages (34)), but also those linking nutritional and social characteristics to understand contemporary food scapes (for example, a database studying modernization of Malaysian food patterns (35)).

According to Leonelli, data is material artefacts which can be mobilized in a specific context of knowledge production (36). Databases thus are information infrastructures, which, according to most practitioners, should represent an open archive of knowledge for the use of many different scientific disciplines (37). According to Bowker, a “working archive” of a database is a tool for management (public health management, in our case), and it requires that “social, political, and organizational context is interwoven with statistics, classification systems and observational results in a generative fashion” (37). Since the distribution of data into the categories largely depends on the context, classification systems are doing social and political work (37).

We build on this perspective, arguing that the current state of affairs in the global campaign for dietary sodium reduction requires new flexible databases. In other words, nutritional classification of sodium consumption factors cannot be translated into an adequate policy, without taking into consideration the social, cultural, and psychological processes influencing salt consumption. We thus argue for the need of categorizing data on salt and sodium consumption around eaters’ practices and relations, rather than around disciplinary or nutritional research questions. Such an eater-oriented approach is useful not only for building comprehensive interdisciplinary health interventions, but also for rendering nutritional knowledge accessible for non-scientific audiences, thus contributing to the increase of consumers’ nutritional knowledge. Our argument resonates with Poulain et al.’s (35) observation that nutritional surveys and studies take an eating individual separately from their context, while the latter provides sociological and ethnological insights into the food habits. Leaving aside the social dimension of food consumption, however, can result in ineffective, and sometimes even contra-effective food policies and regulations. Therefore, linking nutritional knowledge with psycho-socio-cultural determinants requires new flexible knowledge frameworks.

Bowker (37) argues for flexible databases which are “as rich ontologically as the social and natural worlds they map (…)” (ibidem), as databases “shape the world in its image”. Through the analysis of three experimental databases, Wateron (38) has demonstrated that flexible heterogeneous databases include an exposure of the intentions, reflexivity, and policy inscribed inside them, which can be heuristic. In the case of sodium consumption, an effective database would include, at the same time, the interaction of salt with human (linking, perception learning, and body effects), its material dimensions (compositions, formats, and presentation), socio-economic issues (distributions of populations groups most at risk for sodium overconsumption), cultural influences (recipes, traditions, beliefs, and symbolic significations), common salt practices and routines, and knowledge about/attitudes toward food manufacturing and nutritional messages. Our article makes the first step in this direction, building a documentary base² which would merge factors of salt consumption with eaters’ relations and practices, as well as metadata which shapes their representation (methods, units of analysis, subject framing, and geographical distribution of existing knowledge), to suggest guiding categories for salt reduction. In the following section we will expose in detail the process of our documentary base construction.

We have chosen a scoping review approach to answer to our objective of rethinking salt consumption factors through an eater-oriented approach. Scoping reviews aid to explore the range, extent, and nature of existing research approaches, to summarize evidence from multiple disciplines, and to identify research gaps or openings (39, 40), which is necessary for proposing a novel eater-oriented knowledge framework. Tricco et al. (40) and Peters et al. (41) precise that scoping reviews are useful to answer broad research questions, aiming not to compare but rather to describe existing body of work on the issue and present a type of knowledge synthesis. Therefore, scoping review is consistent with our purpose of identifying the openings for eater-oriented databases on salt consumption. Through the exploratory scoping review are able to extract existing nutritional, socio-economic, cultural, material, and socio-psychological determinants and descriptors of salt consumption, synthesizing them into the eater-oriented categories, and relating them to particular methodologies, data sources, and links with nutritional recommendations. The review was conducted within the framework of a French interdisciplinary project Sal&Mieux: Optimizing the use of discretionary salt, however, the scope of our reviewed was broader than only discretionary salt, with interest in the overall appearance of salt in human eating practices. To watch for the review rigor, we have adopted a PRISMA extension for scoping reviews, PRISMA-ScR (40), following the best practices for scoping reviews, identified by Peters et al. (41), as well as the use of scoping reviews in food studies (42–44).

Our search strategy was to extract studies which articulate salt consumption and public health from eater’s perspective across disciplines: health and epidemiology, behavioral and social sciences, nutrition and public health management. The stacked bar chart of disciplinary fields and journals selected for review represents the diversity of disciplines taken into account (Figure 1). The scale of search was limited to articles in English or French³ published between 2000 and 2022. The search line in English was: (“Salt*” OR “Sodium”) AND “Consumption”; (“Salt*” OR “Sodium”) AND “Consumption” AND “Home”; “Salt*” AND ((“Home*” NEAR “Table” OR “Cook*)); “Discretionary salt”; (“Salt*” OR “Sodium”) AND “Consumption” AND “Health”; (“Salt*” OR “Sodium”) AND “Nutrition.” We have used several search engines: general (Google Scholar); specialized in health (ScienceDirect, NCBI PMC, PubMed); specialized in human and social sciences (Persée, CAIRN, JStore and ISIDORE). After the initial search, we have removed the duplicates and searched manually for studies appearing the reference lists of works already included. Eight criteria were used to facilitate the manual search and watch for the diversity of evidence: [1] search engines; [2] combinations of keywords; [3] publication dates; [4] publication outlets; [5] scientific disciplines; [6] research themes; [7] types of data and study designs; [8] the countries of residence of concerned population. We have finally compared our results to the existing reviews on salt and dietary sodium consumption, watching for the inclusion of the major works on the topic.

In the initial screening phase, two researchers⁴ have reviewed the titles, abstracts, and keywords from the resulting documents, coupling them with two expert interviews (with a restaurant chef and his apprentice) and assembling results into a report (45). The report was discussed by a larger scientific consortium of Sal&Mieux to identify eligibility criteria and objectives for the current review article⁵. The further steps, performed by three researchers⁶, consisted of returning to the full texts of the articles from the report and introducing publications from 2021 and 2022, obtained via the same research protocol. We have identified bibliometric data and bibliographic data of each document: authors, types of publication, publication year, DOI, numbers of quotes, summary, methodology, population, countries/territories of origin, institutions). The documents were exported to Zotero software (Zotero version: 6.0.13) for screening for eligibility and categorization.

The following criteria were used for screening for eligibility: 1. original data, 2. scientific or otherwise credible data sources (such as national cohort reports), 3. citated elsewhere, 4. significant sampling size, 5. the study articulates salt consumption and public health. We have also made sure that the retained articles have not been updated by subsequent research results published by the same authors, using a similar methodology and based on a similar sample. All documents, including those left out of the review pool, have been discussed by three researchers⁷ to reach agreement on the pertinence of these works for the research objectives.

We have excluded reports from public agencies, scientific book chapters, and non-peer-reviewed articles. However, we have retained institutional reports based on nutritional epidemiological surveys in France (2, 46, 47) since they have largely informed the initial discussion within the scientific consortium of Sal&Mieux. Although there exists ‘gray literature’ on the use of salt by consumers (by agro-industrial companies or food distributors), we could not access it to include in our exploratory literature review. Our selection, therefore, includes only the sources accessible through academic databases.

We have retained 71 published peer-reviewed articles in French and English based on original data, published between 2000 and 2022. The older articles from medical and experimental sciences (prior to the year 2000) were also included if they marked an emergence of themes, sub-fields, and experimental designs still heavily referred to in contemporary research works (n = 12). Publications from the experimental sciences were selected if they provided insights into the specific salting practices and consumers’ food habits. We also retained physiological works on hedonic acceptability of salt decrease, the regulation of the appetite for salty products, and on the effects of physical activity on such appetite. The studies dealing with the influence of peers or families, as well with the expression of individual food preferences in different contexts were also retained (e.g., parental control, collective influences).

Our next step was to synthesize and categorize retained articles from an eater-oriented perspective, that is on the basis of relations and practices at the frontier of food, diet and health. The goal was to come up with new flexible categories, speaking to everyday eaters’ practices and capable to contain heterogenous multidisciplinary data.

First, we created a descriptive form to extract authors, journal type, disciplinary fields, population and sampling size, salt/sodium sources discussed, methodology and data type, and key findings for each included article. Second, this descriptive form was enriched by two ad-hoc columns: 1. Though what kind of relations/what practices is salt becoming an object of study (what we called “relational features”), and 2. How the study links salt consumption with nutritional recommendations. The entries in these columns were done by three authors⁸ in a collective iterative discussion, after reaching a consensus, as the data was entered into the descriptive form. Finally followed the second round of reading, structured by the relational features and links with nutritional recommendations. In this round, we have synthesized six knowledge fields, ten links with nutritional recommendations, nine relational features, and four thematic categories which describe salt consumption. This was done through a discussion and consensus among the authors. The final result of our categorization process is an eater-oriented documentary base of salt consumption factors, which is accessible in Supplementary Table 1. The following section describes this documentary base in more details.

Five different sources of salt intake, or modalities of salt presence in eaters’ diet, were identified:

To obtain an overview of daily sodium intake from the consumers, the data was mostly collected via dietary recalls before converting food intakes into nutrients, using standard food composition tables¹⁰ (n = 7). Other methodologies included 24-h urine collection tests¹¹ (n = 10) or both dietary recalls and urine collection tests (54–56). One study used data modelling to assess the potential impact of reformulated products on the population salt intake (48). Out of the 39 studies that included table salt use, 21 used frequency scales (from never to always), binary yes/no questions about salt use in general or self-perceived quantities (from too little to too much) to determine salting habits. Some studies only focused on the use of table salt (TS) and cooking salt (CS; n = 7) (51). Some studied baby-food seasoning (57); table salt compensation (28, 58), and the use of a salt shaker (59). Six groups of authors focused on salty foodstuffs only (SF; e.g., industrial food, salty snacks, bread, spreads and dressings) (60–65).

We have extracted from the retained articles nine non-exclusive relational features, that is through what type of relations or practices does the problem of salt consumption emerge:

In some instances, we have accompanied each relational feature with a more specific connotation, such as ‘caregiving practices’, ‘DS use’, ‘commercial value’.

Finally, four ad hoc categories synthesize existing knowledge into the dietary sodium consumption factors: [1] “Socio-demographic and cultural descriptors of salt consumers”; [2] “Knowledge, attitudes, and beliefs on nutritional norms”; [3] “Salt practices associated with dietary or medical regimes”; [4] “Salt materialities: interactions and contexts.” The categories are formulated from the articles’ keywords, titles, research questions and findings. Some formulations, such as ‘descriptors of salt consumers’ or ‘knowledge, attitudes, beliefs’ are taken directly from keywords, titles or results. Others are formulated after reading into summary by three researchers¹². In the latter case, ‘salt materialities’ refer to the translation of salt performances and figuration of salt as both material and symbolic object configured in practice. This is inspired by Bowker and Star’s analysis of classification as a product of action and relations, creating boundaries between communities of practice (66).

The Table 1 synthesizes our corpus through the categories resulting from the scoping review. It includes [1] The four thematic categories. [2] Sampling (representative or randomized). [3] The sources of sodium intake investigated. [4] The type of data or methodology. [5] The relational features with references. The columns and rows of this table were adjusted to map the studies that have similarities to each other.

In each category, we have identified six knowledge fields which articulate salt consumption and health:

We have also identified ten different strategic and methodological approaches to the issue of excessive sodium consumption, which we called ‘links with nutritional recommendations’:

The Table 2 demonstrates the intersections between the research fields represented by specific journals, links with nutritional recommendations, and types of population concerned in the thematic category [1] “Socio-demographic and cultural descriptors of salt consumers.”

In this section we will briefly discuss each thematic category of salt consumption factors, providing an overview of existing knowledge. As the aim of this article is a scoping review to propose an interdisciplinary and eater-oriented knowledge framework, we will not discuss each article individually. The findings of the individual articles can be found in the documentary base presented in the Supplementary Table 1.