Nutri-Score, multiple traffic light and incomplete nutrition labelling on food packages: Effects on consumers’ accuracy in identifying healthier snack options

Highlights

• Consumers’ intuitive evaluation of the healthiness of snack foods is fairly accurate.

• FOP labels lead to greater accuracy in healthiness evaluations.

• The Nutri-Score label has the greatest effect on perceived healthiness.

• The Nutri-Score label is less effective when only displayed on some of the products.

• The effect of FOP labels also depends on the standard used to determine product healthiness.

Abstract

Front-of-package (FOP) nutrition labels are designed to help consumers evaluate the healthiness of foods and to promote healthier food choices. In this study, an online experiment with Swiss consumers (N = 1313) was conducted to compare the effects of different nutrition label formats on consumers’ evaluations of snack food healthiness. Participants were asked to select the healthier option in 105 pairwise comparisons of 15 salty snacks. The participants were randomly assigned to one of five conditions: the FOP presented with (1) the nutrition facts table, (2) the multiple traffic light (MTL), (3) the Nutri-Score, (4) the Nutri-Score on half of the products, or (5) no nutrition information (control). The consumers’ evaluations of the snacks’ healthiness were fairly accurate, even without being given nutrition information on the packaging. The Nutri-Score led to the greatest accuracy in identifying the healthier of two snacks (when using the British FSA/Ofcom nutrient profiling score to determine product healthiness); however, this had only a minimal effect on the evaluation when only some of the products were labelled. Both FOP labels were superior to the FOP with and without the nutrition facts. This indicates that for maximum effectiveness, the labelling of all available products is needed. The perceived usefulness and public support of mandatory implementation were higher for the MTL than for the Nutri-Score label; however, for the latter, perceived usefulness and public acceptance were higher among the participants who became familiar with the label during the experiment than among those who did not.

Introduction

When grocery shopping, consumers are confronted with many different kinds of information on product packaging. In view of the increasingly unhealthy dietary habits in many countries (e.g. increased consumption of energy-dense, highly processed foods and snack products; Jones and Richardson, 2007, Mattes, 2018, WHO, 2003), the provision of unambiguous and comprehensible nutrition information is important. Nutrition labels, particularly those with front-of-package (FOP) positioning, are intended to help consumers evaluate the healthiness of processed foods and thus enable informed food choices (WHO, 2003). In addition to this, it is hoped that the presence of labels on food packages will create an incentive for the food industry to reformulate their products and offer healthier options (Kanter, Vanderlee, & Vandevijvere, 2018) in order to avoid adverse effects on the marketing of their products and negative evaluations of the products themselves.

In recent decades, various nutrition label formats have been introduced (Kanter et al., 2018). These differ in several respects: the types of nutrients on which they focus (e.g., highlighting only critical nutrients or also considering health-promoting nutrients), the kind of presentation/design features they use (e.g., using numbers, colour codes, shapes, or letters), and how directive they are (Hodkins et al., 2009). The mandatory nutrition facts table on the back of the package can be considered a nondirective label because it provides detailed numerical information about the nutritional components of a product without explicitly evaluating the product’s healthiness. Semidirective nutrition labels, such as the multiple traffic light (MTL) signpost, use visual cues such as colour codes or symbols to communicate an evaluation of the product’s critical nutrient content. On the MTL label, each nutrient attribute (the amount of fat, saturated fatty acids, sugar, and salt/sodium) is represented by a separate symbol that indicates whether the amount is low (green), medium (amber), or high (red). These labels do not provide a global evaluation of the product’s healthiness. Directive labels, by contrast, provide a summary evaluation of the healthiness of a product without any detailed information. These summary labels include simple labels placed only on foods that meet certain healthiness criteria (e.g., Keyhole, Green Tick, and Choices labels) and graded labels (e.g., Nutri-Score and Health Star Rating labels) (Julia & Hercberg, 2017).

According to epidemiological nutrition research, healthy diets contain plenty of fruit, vegetables, fibre, plant-based sources of fat and protein, and low amounts of fat, saturated fat, total sugar, and salt, among others (Willett & Stampfer, 2013). A relatively new method, nutrient profiling (NP), enables the evaluation and ranking of food products according to the healthiness of their nutritional composition (WHO, 2017). Various NP models exist, such as the Ofcom/FSA NP model (Food Standards Agency, 2011) and the Health Canada Surveillance Tool (HCST) tier system (Health Canada, 2014). Each of these models includes a different number of health-relevant nutrients and serves as a basis for the classification schemes on nutrition labels and the determination of food-related health taxes (Rayner, 2017). Currently, there is no consensus regarding which model should be considered the gold standard for objectively defining the healthiness of foods (Poon et al., 2018). However, the Ofcom/FSA NP model is one of the most well-known and well-validated models (Rayner, 2017), and it is considered the gold standard by a growing number of countries and food producers, which are introducing the Nutri-Score (the label based on this model) to communicate the healthiness of products to consumers in a simple way.

Numerous studies have evaluated the impact of different nutrition labels on consumers’ perceptions of the healthiness of foods and have sought to determine which of the available formats is the best means of communicating nutrition information (e.g., Borgmeier and Westenhoefer, 2009, Egnell et al., 2018, Gorski Findling et al., 2018, Hawley et al., 2013, Hersey et al., 2013, Hodkins et al., 2009, Jones and Richardson, 2007, Julia and Hercberg, 2017, Roberto et al., 2012, Siegrist et al., 2019, Watson et al., 2014).

Studies based on eye-tracking methods have suggested that compared to the standard nutrition facts panel, FOP labels, especially those that use a traffic light system, are better able to catch consumers’ attention and direct their attention to the nutrients most relevant to healthiness assessments (Becker et al., 2015, Jones and Richardson, 2007, van Herpen and Trijp, 2011). This may be due to the more prominent placement of such FOP labels and their design features (Becker et al., 2015). Similarly, the results of another eye-tracking study (Siegrist, Leins-Hess, & Keller, 2015) suggest that the visual information processing of the MTL label is more efficient overall than that of the Guideline Daily Amounts (GDA) and the nutrition facts table; in this study, the MTL label was processed more quickly than the GDA label (but less quickly than the nutrition facts table), and participants focussed on more relevant information when reading both the MTL label and the GDA than when reading the nutrition facts table. The nutrition facts table contains only numerical information, which can be difficult to understand, especially for consumers who have limited literacy skills (Campos et al., 2011, Roberto and Khandpur, 2014). Consequently, several studies that compared different label formats have found that the MTL system resulted in more accurate healthiness evaluations compared to no label and other label formats, such as the GDA and the simple ‘healthier choice’ tick (Borgmeier and Westenhoefer, 2009, Roberto et al., 2012); however, other studies did not find substantial differences between different types of FOP labels (Hodgkins et al., 2015, Watson et al., 2014). More recent studies have included the new Nutri-Score label, which was developed in France (Julia & Hercberg, 2017). This label provides a graded, colour-coded summary evaluation of a product’s healthiness, ranging from dark-green A (healthiest) to dark-red E (least healthy) and considers the content of various health-promoting and critical ingredients. Previous findings have suggested that this label is easier for consumers to understand and results in more accurate healthiness evaluations than the MTL and other labelling systems (Ducrot et al., 2015, Egnell et al., 2018). However, Gorski Findling et al. (2018) found that the MTL led to greater accuracy in identifying the healthier of two foods compared to a labelling scheme based on 0–3 stars, another type of graded summary label.

Previous studies have differed widely in terms of their design, the labels (or versions of labels) compared, the food categories used, and how the stimuli were presented to the consumers. For example, many previous studies did not use real brands available in supermarkets (Borgmeier and Westenhoefer, 2009, Egnell et al., 2018, Watson et al., 2014) or presented labels only, without the products themselves (Hieke and Wilczynski, 2012, Jones and Richardson, 2007); both of these scenarios make the decision situation less realistic. Furthermore, few studies so far have included the Nutri-Score label (Julia & Hercberg, 2017). One study investigated the effect of the Nutri-Score on the healthiness of food purchases in experimental supermarkets (Julia et al., 2016) but found no effect for salty snacks. To the best of our knowledge, no studies have investigated the impact of nutrition labels on consumers’ perceptions of the healthiness of a realistic set of salty snack foods from existing brands.

The results of all the studies we are aware of were based on the assumption that all available products carry a label and can therefore be compared by consumers. However, in many cases, the implementation of nutrition labels is not mandatory (Buttriss, 2018, Kanter et al., 2018); thus, it is likely that situations occur in which only some of the available products are labelled. In Switzerland, for example, the French food company Danone recently began to place the Nutri-Score label on all their dairy products (Danone, 2019), whereas other producers of dairy products have not implemented it. This raises the question of whether nutrition labels such as the Nutri-Score are equally effective when they are not present on all available products. To the best of our knowledge, no previous studies have investigated the effectiveness of a nutrition label under the condition of incomplete labelling.

The present study had several aims. The first was to compare two interpretive FOP nutrition labels (MTL and Nutri-Score) in terms of their effect on consumers’ healthiness evaluation of salty snacks, as well as to compare these labels with the standard nutrition facts table and the absence of nutrition information. In order to create a relatively realistic shopping-choice situation (with high ecological validity), a range of snacks offered by the same Swiss retailer, all of which are real brands available at stores, were used. We focussed on salty snacks because this product category is highly relevant, considering that snacking contributes nearly one-third to European consumers’ daily energy intake (Mattes, 2018). In addition, salty snacks usually contain critical amounts of sodium, fats, and sugar (Foundation, 2016). Nevertheless, this product category offers some variability in terms of healthiness, which makes it appropriate for the purpose of the present study. The second aim of this study was to investigate whether the effectiveness of the Nutri-Score label differs when it appears on only some products. Moreover, this study explored, among a representative sample of Swiss consumers, the perceived usefulness of the Nutri-Score and the MTL labels compared to the nutrition facts table and the ingredients list, as well as public support for the mandatory introduction of these two labels.