Effectiveness of subsidies in promoting healthy food purchases and consumption: a review of field experiments

Objective: To systematically review evidence from field interventions on the effectiveness of monetary subsidies in promoting healthier food purchases and consumption. Design: Keyword and reference searches were conducted in five electronic databases: Cochrane Library, EconLit, MEDLINE, PsycINFO and Web of Science. Studies were included based on the following criteria: (i) intervention: field experiments; (ii) population: adolescents 12-17 years old or adults 18 years and older; (iii) design: randomized controlled trials, cohort studies or pre-post studies; (iv) subsidy: price discounts or vouchers for healthier foods; (v) outcome: food purchases or consumption; (vi) period: 1990-2012; and (vii) language: English. Twenty-four articles on twenty distinct experiments were included with study quality assessed using predefined methodological criteria. Setting: Interventions were conducted in seven countries: the USA (n 14), Canada (n 1), France (n 1), Germany (n 1), Netherlands (n 1), South Africa (n 1) and the UK (n 1). Subsidies applied to different types of foods such as fruits, vegetables and low-fat snacks sold in supermarkets, cafeterias, vending machines, farmers' markets or restaurants. Subjects: Interventions enrolled various population subgroups such as school/university students, metropolitan transit workers and low-income women. Results: All but one study found subsidies on healthier foods to significantly increase the purchase and consumption of promoted products. Study limitations include small and convenience samples, short intervention and follow-up duration, and lack of cost-effectiveness and overall diet assessment. Conclusions: Subsidizing healthier foods tends to be effective in modifying dietary behaviour. Future studies should examine its long-term effectiveness and cost-effectiveness at the population level and its impact on overall diet intake.