The influence of sugar taxes and front-of-package nutrition labels on consumer purchasing behaviours: a randomized experimental marketplace

Abstract

Background: Poor dietary intake remains one of the leading causes of non-communicable disease in Canada and globally. In response, sugar taxes and front-of-package (FOP) nutrition labelling systems are increasingly being implemented around the world with the intention of improving dietary intake and reducing the associated health and economic impacts of diet-related non-communicable disease. However, there is relatively little experimental data on how these strategies influence consumer behaviour and how different policy measures—such as taxes and FOP labels—may interact. In addition, policymakers who implement these measures must decide what type of tax structure or FOP format to use; however, the relative impact of different tax structures or FOP labels on food and beverage purchases remains unclear. Objectives: This dissertation examined the following research questions: (1) do different FOP labels and sugar taxes influence consumer purchases of sugars, sodium, saturated fats, or energy?; (2) do different sociodemographic or individual characteristics moderate the effects of FOP labels and sugar taxes on participants’ purchasing of sugars, sodium, saturated fats, or energy?; (3) how do consumers’ purchases of specific product categories vary across different FOP labelling systems?; and (4) how do consumers’ purchases of specific product categories vary across different sugar taxation formats? Methods: An experimental marketplace study was conducted from March 12 – May 20, 2018. A final sample of 3,584 Canadians 13 years and older participated in the 5 (FOP label condition) × 8 (tax condition) between-within group experiment. Participants received $5 and were presented with images of 20 beverages and 20 snack foods available for purchase. Participants were randomized to one of five FOP label conditions (no label; ‘high in’ nutrient symbol; multiple traffic light (MTL); health star rating (HSR); nutrition grade) and completed eight within-subject purchasing tasks with different taxation conditions (beverages: no tax, 20% tax on sugar-sweetened beverages (SSBs), 20% tax on sugary drinks, tiered tax on SSBs, tiered tax on sugary drinks; snack foods: no tax, 20% tax on high-sugar foods, tiered tax on high-sugar foods). Upon conclusion, one of eight selections was randomly chosen for purchase, and participants received the product and any change from the $5. In Paper 1, analyses compared the sugars, sodium, saturated fats and calorie content of participants’ purchases across tax and labelling conditions. Paper 2 investigated the main and moderating effects of individual-level characteristics on participants’ purchases of sugars, sodium, saturated fats and calories. Paper 3 evaluated participants’ purchases of five specific product categories that received conflicting ratings across FOP label conditions. Paper 4 assessed the impact of the tax conditions on participants’ purchases of two relevant product categories (moderately sugary beverages and 100% fruit juice). Results: Paper 1 – Overall, there were significant differences in the nutrient levels of participants’ purchases across several of the experimental conditions. Compared to those who saw no FOP label, participants who viewed the ‘high in’ symbol purchased less sugar (− 2.5 g), saturated fat (− 0.09 g), and calories (− 12.6 kcal) in the beverage purchasing tasks, and less sodium (− 13.5 mg) and calories (− 8.9 kcal) in the food tasks. All taxes resulted in substantial reductions in mean sugars (− 1.4 to − 4.7 g) and calories (− 5.3 to − 19.8 kcal) purchased, and in some cases, reductions in sodium (− 2.5 to − 6.6 mg) and saturated fat (− 0.03 to − 0.08 g). Taxes that included 100% fruit juice (‘sugary drink’ taxes) produced greater reductions in sugars and calories than those that did not. Paper 2 – There were few moderating effects of individual-level characteristics on the nutrient content of participants’ purchases. Participants who were younger, male, and more frequent consumers of sugary drinks tended to purchase products containing more sugars, sodium, saturated fats and calories. Sex and age moderated the relationship between tax condition and sugars or calories purchased: female participants were more responsive to a tax that included fruit juice compared to males, and younger participants were more responsive to all sugar tax conditions compared to older participants. Reported thirst and education level also moderated the relationship between tax condition and calories purchased. Paper 3 – Participants’ purchases of products that received conflicting ratings varied across some FOP label conditions. Participants who saw the HSR were more likely to purchase 100% fruit juice (compared to MTL) and cheese snacks (compared to no label and ‘high in’). The ‘high in’ label led to fewer purchases of chocolate milk compared to no label. Diet beverage purchases were higher in all FOP conditions relative to no label. Paper 4 – Participants’ responses to the different tax structures were as hypothesized. The odds of purchasing a moderately sugary beverage were higher under tiered versus non-tiered taxes, while purchases of high sugary beverages differed very little under tiered versus non-tiered. The odds of purchasing 100% fruit juice were lower when these products were included in a tax versus when they were not. Conclusions: This study expands the evidence indicating that sugar taxation and FOP labelling strategies can promote healthy food and beverage choices. All sugar taxes were effective at reducing the sugars and energy content of participants’ beverage and snack food purchases; however, some formats, including those that taxed 100% fruit juice, were more effective than others. The results suggest that two key tax formats are likely to function as hypothesized: taxes that include 100% fruit juice products may lead to fewer purchases of fruit juice, and taxes that incorporate multiple tiers may encourage purchases of moderately sugary products to a greater extent than non-tiered formats. The FOP nutrition labels demonstrated smaller—but nevertheless meaningful—effect sizes relative to the taxes, and results were more variable across formats, with the ‘high in’ FOP labels exhibiting the greatest impact. Results also suggest that, despite some similarities, existing FOP systems differ in the extent to which they promote or dissuade common food categories. ‘High in’ and MTL systems may more effectively discourage purchases of products contributing negative nutrients than HSR or nutrition grade systems. Few individual-level characteristics moderated the effects of sugar taxes or FOP labels on nutrients purchased in this study, suggesting that these policies may produce similar effects across key sociodemographic groups. Overall, the results of this experimental study are consistent with evidence from other studies in suggesting that both taxes and FOP nutrition labels have the potential to generate meaningful reductions in the intake of sugars and other nutrients of public health concern. The magnitude of effects observed in this study suggest that sugar taxes and ‘high in’ labels could significantly reduce non-communicable disease at a population level, but would generate even greater improvements when implemented alongside other strategies to improve the food environment.