Impact of Taxation and Subsidies on the Nutrition Quality of Purchases in an Online Experimental Supermarket, Overall and by Income Level: a Randomized Control Trial

Scientific context The increase in the consumption of unhealthy food coupled with a suboptimal consumption of healthier options have increased the risk of non-communicable diseases (NCD) worldwide. Among other public policies to address the rise in NCD -such as front of pack labelling, regulation of food and beverages in schools, marketing regulations targeted to children- taxation has been recognized as a cost-effective strategy to reduce consumption of taxed products. Although subsidies have been used to reduce food insecurity, with the rise in NCD associated with unhealthy diets, studies have explored the feasibility of combining subsidies to incentivize the consumption healthy food with taxes on unhealthy options. The impact of prices on dietary behaviour of consumers has been demonstrated in experimental designs as well as in economic analysis of observational data on purchases. Although some experimental studies have been used to study the impact of taxation and subsidies among specific populations in France, none has evaluated the impact in the general population.

Objective The aim of the study is to evaluate the impact of implementing taxes on unhealthy food and beverages and subsidies to healthy food, separately and combined, on the nutritional quality of purchases, overall and by income level, in an experimental online supermarket.

Intervention description: The intervention includes taxation of lower nutritional quality products (identified using the front-of-pack nutrition label Nutri-Score - classes D and E) and/or subsidies for products of higher nutritional quality (identified as raw products or Nutri-Score A and B).

Design The intervention will be a parallel arm randomized trial stratified by income against a control situation with no changes in prices and the presence of the Nutri-Score on-pack for all pre-packed products in all interventions (control, taxes and subsidies).

Expected public health impact: This study will allow to investigate the potential synergistic effect on the nutritional quality of food choices of combining taxation and income-based subsidies in a context of social inequalities in rising non-communicable disease associated with poor diets. Following a proportional universalism perspective, income-based subsidies can mitigate the regressivity of taxation according to income. As no countries have implemented this combination of fiscal policies to improve diets, the results of this study will contribute to the scientific knowledge on the topic and will provide preliminary results to decision makers.