Introduction

Non-sugar sweeteners (NSS) are a functional class of food additives (FA) defined in Brazil as substances other than sugars that provide a sweet taste to foods and beverages [1]. Originally developed as non-caloric substitutes for sugars [2] they are currently in widespread use, mainly as a component of ultra-processed food products (UPFP), either alone or combined with added sugars [3].

UPFP is a food category defined by the Nova classification [4] and the presence of a NSS is considered a marker to identify UPFP, as they belong to the class of food additives with cosmetic functions. Those types of food additives are used to make the final product palatable or hyper-palatable, and include substances such as flavorings, flavor enhancers, colorings, emulsifiers, emulsifying salts, thickeners, antifoaming, bulking, carbonating, foaming, gelling and glazing agents, besides NSS [3]. Global UPFP consumption has increased over the past decade, and a consolidated body of scientific evidence associates these products with negative health outcomes [5–11]. These findings support the recommendations of the Brazilian Dietary Guidelines, which advise avoiding the consumption of UPFP and prioritizing fresh or minimally processed foods, as well as culinary preparations made from them [12].

In response to growing evidence and following a systematic review and meta-analysis on NSS use [13], the World Health Organization (WHO) published new guidelines in 2023 conditionally recommending against the use of NSS for weight control or to reduce the risk of developing non-communicable diseases (NCD) [14]. These guidelines underscores two gaps in Brazil’s labeling policy: the presence of NSS is currently disclosed only in the ingredients list, a section that is often difficult for consumers to locate and interpret [15], and the absence of NSS-specific information in the mandatory front-of-package nutrition labels (FoPNL). Recent evidence associates the consumption of NSS with potential health risks [13], such as glucose intolerance and alterations in the intestinal microbiota, which can lead to metabolic abnormalities (including pancreatic endocrine dysfunction [16–18]. NSS intake has been associated with the worsening of kidney disease [19], as well as an increased risk of cancer [20] and adverse cardiovascular outcomes [21]. Specifically, the consumption of aspartame, sucralose, saccharin and acesulfame potassium are associated with alterations in normal physiological processes involved in the absorption and metabolism of nutrients, contributing to increased abdominal adiposity and body mass index (BMI) in adults and older individuals [22–24].

Given the potential health risks associated with NSS, developing effective strategies to highlight this information on product labels is crucial. Warning labels are an effective strategy to empower consumers by enhancing their understanding of the composition of packaged food products and supporting healthier food choices [25–27], by mitigating the influence of health and nutrition claims [28]. For a warning to effectively communicate risk, it must include graphic elements that enhance visibility and comprehension [29]. Since the environment of a product package includes branding, marketing elements and nutrition claims [30], warning labels must clearly stand out by using specific design features such as shape, size, typography, and layout to ensure visibility, readability, and comprehension [31]. Color also plays a critical role, with black being the most used color for regulatory warnings in nutrition labeling. The literature further suggests that such messages should begin with a signal word, such as “Attention” or “Caution” [32–35].

Based on a public health and consumer rights approach, Argentina and Mexico have enacted legislation mandating warnings (cautionary legend) for the presence of NSS in packaged foods and beverages [36,37]. These NSS warnings are accompanied by advice against children’s consumption and displayed in a black rectangle, with white lettering, making it stand out compared to other packaging elements.

To consider a labeling proposal within the Brazilian FoPNL context, it is necessary to connect with the Chilean experience. Chile was the first country to approve and implement a FoPNL for nutrients in excess (e.g., High in sodium) [38]. The Chilean Food Labeling and Advertising Law represents a significant advancement in this area; however, it lacks a warning to indicate the presence of NSS. Following its implementation, the country experienced widespread UPFP reformulation, characterized by the total or partial replacement of added sugars with NSS, to keep the sweet taste of products. As a result, an increasing number of UPFP became available without the “high in sugar” FoPNL [39,40]. In 2020, Brazil approved a new nutrition labelling regulation, which mandates a FoPNL featuring a magnifying glass icon and the expression “high in” for three nutrients of concern: added sugar, saturated fat and sodium [41,42]. Similar to Chile, the Brazilian FoPNL does not include a warning for NSS and based on the Chilean experience, it is expected that the same reformulation will occur in the Brazilian market.

To uphold the right to information and in light of WHO guidelines and the NSS labeling models in Argentina and Mexico, it is essential to develop a specific NSS labelling strategy for the Brazilian population. This strategy should ensure clear, visible and easy-to-interpret information, enabling consumers to make more informed and potentially healthier food choices. In this context, the present study aimed to evaluate experts’ opinions on specific attributes of proposed NSS warning labels designed to inform consumers about the presence of NSS in packaged foods and beverages sold in Brazil.

Materials and methods

Material and procedures

The panel of experts was conducted online on October 3, 2023, from 4 pm to 6 pm, via the Google Meet platform. The session was moderated by four researchers involved in the study. An online questionnaire, administered via Google Forms during the meeting, was used to collect individual responses. Experts provided consent for your participation by completing the consent form previously sent. The entire meeting was recorded and transcribed for subsequent content analysis.

The two-hour meeting was divided into three sessions (30 minutes each), in addition to an initial moment (15 minutes) to greet the experts’ and firm the agreements, and a final moment (15 minutes) to close the session. The sessions were interconnected, with the outcomes of one influencing the next. To conduct the panel, a mediation guide (S1 File) was developed, covering the following topics: evaluation of the warning message for NSS, evaluation of label readability and evaluation of label visibility in the context of packaging.

Different Google Forms (S2 File) were developed and shared through the meeting chat during each session. Experts submitted their responses anonymously prior to group discussions. Since the session involved the evaluation of visual elements (e.g., label mockups), participants were required to use a laptop or desktop computer. In each session, a Google Form link was shared with the participants and, after completing the questionnaire individually, the experts presented and justified their choices in a group debate. Transition to the next session required agreement on the previous topic, as each step built upon the previous findings. The first session aimed to evaluate the content of the warning message for non-sugar sweeteners, the second to evaluate the readability of the chosen message within a warning model, and the third to evaluate the visibility of the message within a warning model in the context of product mockup packaging.

The first session (evaluation of the NSS warning message) aimed to identify the most appropriate sentence for the NSS warning label, based on the expert’s opinions (Fig 1).

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Fig 1. Sentences to be evaluated by the experts based on the best message to indicate the presence of NSS in food products.

https://doi.org/10.1371/journal.pone.0331302.g001

Based on the first session’s discussion, the second session addressed label readability. Experts assessed the visual presentation of the NSS warning label, with an emphasis on readability and attention capture. Participants were shown different label formats and asked to indicate which version was more readable and more attention-grabbing (Fig 2).

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Fig 2. Examples of NSS warning labels to evaluate the readability and attention by the experts.

Note: The texts in Portuguese language are the same as those shown in Fig 1.

https://doi.org/10.1371/journal.pone.0331302.g002

The third and last session (assessment of label visibility in the context of packaging) aimed to analyze NSS warning labels on food and beverage mockups, positioned in different locations. Two previous studies were considered to select the food categories of the mockups: Brazilian Household Budget Survey (Pesquisa de Orçamentos Familiares – POF) from 2008–2009 and from 2017–2018 [45], and a Chilean study, which brings the food categories whose use of NSS increased after the implementation of the Food Labeling and Advertising Law [40]. Four product categories were chosen: ready to drink fruit juice, sandwich biscuit, dairy drink and fermented milk. Labels were shown in the following positions: (A) main panel near the FoPNL, (B) main panel near the product name, and (C) back panel near the ingredient list and allergen warnings (Fig 3).

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Fig 3. Food and beverage mockups with different positions of NSS warning label.

(A) main panel and near the FoPNL. (B) main panel and near to sales denomination. (C) back panel and near to list of ingredients and allergen warning.

https://doi.org/10.1371/journal.pone.0331302.g003

In the final form, experts were asked to individually rank each label configuration based on visibility and attention. The session concluded with a final group discussion, informed by the ranking results.

Data analysis

Results

The panel was formed by 10 experts from different knowledge areas, such as: nutrition (n = 4), social communication (n = 1); information design (n = 1), law (n = 1), pharmacy (n = 1), medicine (n = 1) and psychology (n = 1). Participants were from different Brazilian macroregions: Southeast (n = 5), South (n = 2), Northeast (n = 1) and Central-West (n = 1).

Based on the results of the individual questionnaire and the collective discussion, some changes in expert opinion were observed. The predefined questions in the Google Forms focused on technical attributes of design (readability, visibility and attention) and health (perception of healthiness and health risk). In contrast, the collective discussion introduced and prioritized emerging aspects, such as inferences about Brazilian consumers’ opinions, design and the expert’s technical personal preference.

Regarding the NSS warning label message, “ATTENTION: CONTAINS NON-SUGAR SWEETENER: NOT RECOMMENDED FOR CHILDREN AND FOR WEIGHT CONTROL” (“ATENÇÃO: CONTÉM EDULCORANTE - NÃO RECOMENDADO PARA CRIANÇAS E PARA CONTROLE DE PESO”, in Portuguese) was selected in the individual questionnaire as the one that makes products seem less healthy (n = 4), makes products seem more harmful to health (n = 6) and attracts the most attention (n = 6). The second most selected message was “ATTENTION: CONTAINS NON-SUGAR SWEETENER” (ATENÇÃO: CONTÉM EDULCORANTE, in Portuguese), with the following responses: makes products seem less healthy (n = 3), makes products seem more harmful to health (n = 1) and attracts the most attention (n = 2).

During the collective discussion, the message “ATTENTION: CONTAINS SWEETENER” (“ATENÇÃO: CONTÉM EDULCORANTE”, in Portuguese) was selected as the most appropriate. The shift in experts’ opinion was attributed to several concerns: how Brazilian consumers would interpret a lengthy message, the potential for the message’s size to either draw or deter consumer attention in the packaging context, and whether a non-recommendation statement could broaden or narrow the target audience of the warning.

Given the interconnected structure of the sessions, the second session presented two NSS warning label variations, both using the message “ATTENTION: CONTAINS NON-SUGAR SWEETENERS” (“ATENÇÃO: CONTÉM EDULCORANTE”, in Portuguese). The difference between the proposals was in typographic emphasis: one version had the entire sentence in bold, while the other emphasized in bold only the word “attention” (“atenção”, in Portuguese), as illustrated in Fig 2. No consensus was reached in this session, so both versions were carried forward to the next one.

In the third session, the same two warning proposals were displayed in the context of packaging (Fig 3). Based on both individual questionnaire (Table 1) and the collective discussion, the position next to the FoPNL was considered the most appropriate.

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Table 1. Ranking of NSS warning positions on labels.

https://doi.org/10.1371/journal.pone.0331302.t001

Considering the content analysis of the collective discussion, the most frequently referenced codes were: attributes of NSS warning labels (n = 26), the attribute of the word “attention” attracting attention (n = 17), use of the word “attention” as a signal (n = 11), and the notion of non-recommendation for NSS consumption (n = 11). The most frequent codes were related to the specific characteristics of the warning label proposals, the design elements and the message of non-recommendation. Conversely, the least frequently referenced codes were: perception of healthiness and/or health risk (n = 7), inference about consumers opinions (n = 9), and expert’s personal preference/opinion (n = 9), as shown in Table 2. The limited number of references about perception of healthiness and/or health risk is noteworthy, given that is one of the technical attributes experts were asked to evaluate and considering that seven of the participants were health professionals.

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Table 2. Codes, subcodes, description and number of references that emerged through the content analysis of the panel of experts.

https://doi.org/10.1371/journal.pone.0331302.t002

Discussion

In Brazil, food labeling regulation is coordinated by Anvisa, the national agency responsible for regulating, overseeing and inspecting products and services that pose potential risks to public health. The regulatory process includes the contributions from government, academia, civil society organizations and industry. The most recent review of nutrition labeling regulations, which lasted six years, approved the mandatory FOPNL [41,42]. Despite this, a specific warning for NSS was not adopted with Anvisa stating that NSS labeling would be defined in the MERCOSUR agenda. Currently, Anvisa is leading a new regulatory agenda to revise NSS labeling and use, which is a concrete window of opportunity to discuss this topic. In 2024, the agency published a regulatory discussion paper and held technical meetings with stakeholders, including the food industry, academia and civil society, which highlights the potential for improvement of NSS labeling and proposes the inclusion of a front-of-package warning, particularly addressing contraindications for children [47]. The results of this study will be presented in due course within the ongoing regulatory process, with the aim of informing decisions related to public health and the right to information. It is important to recognize that this proposal may be vulnerable to industry interference, as evidenced during the nutrition labeling process [48]. In addition to the labeling proposal, it is essential that the government commits to implementing public awareness campaigns on the topic, particularly to educate the population about the true meaning of the term “edulcorante”.

The use of food additives in products has been increasingly studied in the last decade. A study assessing the list of ingredients of foods and beverages available on the Brazilian market identified that of 9,856 products, 20.6% contain no food additives, 11.6% contained one additive, 19.8% contained between two and three, 23.2% contained between four and five and 24.8% six or more. The study also identified patterns of food additives combinations, with the fifth pattern being exclusively represented by NSS, which was associated with the following product categories: sugar and other non-caloric sweeteners, fruit-flavored drinks and other beverages. Currently, the most frequent food additives category in products sold in Brazil is flavoring [49]. This highlights the importance of improving information about NSS, particularly since such details are currently confined to the ingredients list, which, despite being regulated, pose comprehension barriers for many consumers [15].

Several factors support the call for more transparent labeling of NSS in Brazil. These include the Chilean experience [39,40]; increasing evidence on the potential health risks associated with NSS consumption [13]; the WHO`s conditional recommendation regarding NSS intake [14]; and the absence of any specific NSS warning in the current Brazilian FoPNL system [41,42].

In contrast to regulated information, advertising claims on packaging often receive greater visual emphasis. Evidence shows that visual elements on labels interfere in the perception of products’ healthiness [50,51], while FoPNL implementation has been linked to decreased perception of healthiness. To date, however, there are no studies that evaluated Brazilian consumers’ perception of NSS warning labels.

One study involving 448 Brazilian consumers found that FoPNL reduced the perceived healthfulness of certain packaged products (e.g., chocolate milk with granola, mate tea with cookies). However, familiar brands and textual nutritional marketing claims also have a significant effect on the perception of healthiness [52]. This demonstrates that while FoPNL helps consumers identify highlighted nutrients, marketing strategies still shape perceived healthfulness.

In Mexico, studies have found that NSS warning labels reduce parents’ perceptions of a product’s healthfulness more effectively than excess sugar warning alone [53], and the presence of NSS warning influences the healthiness perception of beverages for youth [54]. Such findings support the potential role of NSS-specific warning labels in improving consumer understanding of product nutrition content. It is important to highlight that the presence of NSS in a product characterizes it as an UPFP, a group consistently associated with negative health outcomes [5–11].

While evidence on NSS-specific labeling remains limited, data from Mexico suggest that such labels can reduce the perceived healthiness of UPFPs. Given the likelihood that UPFPs in Brazil may be reformulated by replacing added sugars with NSS following FoPNL implementation, it is crucial to ensure that consumers are provided with clear, accessible information.

The findings from this expert panel represent the initial phase of a broader study designed to assess the effectiveness of NSS warning labels in enabling the identification of NSS in packaged foods and beverages in Brazil. These results will inform the subsequent phase, which involves conducting focus groups with consumers from three distinct regions of the country. Data obtained from the qualitative phases will guide the design of a final quantitative study involving a nationally representative sample of Brazilian consumers.

This study has limitations. Conducting the expert’s panel virtually may have hindered the ability to fully capture non-verbal communication, which could indicate unspoken disagreement, especially in instances where a dominant view was expressed by most participants. Although consensus was not a requirement, it was reached in first and third session. In the second session, the absence of consensus was not detrimental, as it resulted in two proposals being forwarded to session three for further analysis. Additionally, despite efforts to diversify the group, it was challenging to recruit experts from different fields across the country with specific expertise on the topic. Nonetheless, purposive sampling enabled the inclusion of a diverse panel of professionals based in various Brazilian cities.

Conclusion

The study provides interdisciplinary evidence and expert insight, to support the development of NSS warning labels in Brazil. Considering the individual questionnaire and the content analysis of collective discussion, the experts’ decision about the most appropriate NSS warning label was: “attention: contains non-sugar sweetener - not recommended to children and for weight control” (Atenção: contém edulcorante – não recomendado para crianças e para controle de peso, in Portuguese) and “attention: contains non-sugar sweetener” (Atenção: contém edulcorante, in Portuguese). Experts recommended that these messages be displayed in bold and positioned on the main panel, near the FoPNL.

Supporting information

Acknowledgments

To all the experts who voluntarily participated in the panel and shared their knowledge of this study and to the Pan American Health Organization (PAHO).