Abstract
BackgroundWhile food pricing is a promising strategy to improve diet, the prospective impact of food pricing on diet has not been systematically quantified.ObjectiveTo quantify the prospective effect of changes in food prices on dietary consumption.DesignWe systematically searched online databases for interventional or prospective observational studies of price change and diet; we also searched for studies evaluating adiposity as a secondary outcome. Studies were excluded if price data were collected before 1990. Data were extracted independently and in duplicate. Findings were pooled using DerSimonian-Laird's random effects model. Pre-specified sources of heterogeneity were analyzed using meta-regression; and potential for publication bias, by funnel plots, Begg's and Egger's tests.ResultsFrom 3,163 identified abstracts, 23 interventional studies and 7 prospective cohorts with 37 intervention arms met inclusion criteria. In pooled analyses, a 10% decrease in price (i.e., subsidy) increased consumption of healthful foods by 12% (95%CI = 10–15%; N = 22 studies/intervention arms) whereas a 10% increase price (i.e. tax) decreased consumption of unhealthful foods by 6% (95%CI = 4–8%; N = 15). By food group, subsidies increased intake of fruits and vegetables by 14% (95%CI = 11–17%; N = 9); and other healthful foods, by 16% (95%CI = 10–23%; N = 10); without significant effects on more healthful beverages (-3%; 95%CI = -16-11%; N = 3). Each 10% price increase reduced sugar-sweetened beverage intake by 7% (95%CI = 3–10%; N = 5); fast foods, by 3% (95%CI = 1–5%; N = 3); and other unhealthful foods, by 9% (95%CI = 6–12%; N = 3). Changes in price of fruits and vegetables reduced body mass index (-0.04 kg/m2 per 10% price decrease, 95%CI = -0.08–0 kg/m2; N = 4); price changes for sugar-sweetened beverages or fast foods did not significantly alter body mass index, based on 4 studies. Meta-regression identified direction of price change (tax vs. subsidy), number of intervention components, intervention duration, and study quality score as significant sources of heterogeneity (P-heterogeneity<0.05 each). Evidence for publication bias was not observed.ConclusionsThese prospective results, largely from interventional studies, support efficacy of subsidies to increase consumption of healthful foods; and taxation to reduce intake of unhealthful beverages and foods. Use of subsidies and combined multicomponent interventions appear most effective.
Highlights
To address these key gaps in knowledge, we systematically investigated and quantified the prospective, empirical effects of change in food price on dietary consumption, and how key additional interventions might modify these effects
We followed the recommendations of the Meta-analysis of Observational Studies in Epidemiology (MOOSE)[15] and of Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)[16] guidelines in all stages of the design, implementation, and reporting of this meta-analysis (S1 File)
We included studies of multicomponent interventions if studies reported the effect of the price change separately or if the price change was a major component of the intervention
Summary
Poor diets are the leading risk factor for mortality and morbidity globally.[1, 2] The World Health Organization and the United Nations General Assembly have called for adoption and implementation of evidence-based government policies to improve diet.[3,4,5,6] Whereas fiscal measures such as taxation and subsidies have been proposed as effective strategies,[3,4,5,6] most prior evidence of their efficacy for changing diet is derived from cross-sectional modeling studies.[7,8,9] Such studies provide important information on potential effects of fiscal policies, but may have more limited ability to draw conclusions about the prospective effect of actual price changes on actual changes in consumption. While food pricing is a promising strategy to improve diet, the prospective impact of food pricing on diet has not been systematically quantified
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