Are interventions to promote healthy eating equally effective for all? Systematic review of socioeconomic inequalities in impact.
BACKGROUND
Interventions to promote healthy eating make a potentially powerful contribution to the primary prevention of non communicable diseases. It is not known whether healthy eating interventions are equally effective among all sections of the population, nor whether they narrow or widen the health gap between rich and poor. We undertook a systematic review of interventions to promote healthy eating to identify whether impacts differ by socioeconomic position (SEP).


METHODS
We searched five bibliographic databases using a pre-piloted search strategy. Retrieved articles were screened independently by two reviewers. Healthier diets were defined as the reduced intake of salt, sugar, trans-fats, saturated fat, total fat, or total calories, or increased consumption of fruit, vegetables and wholegrain. Studies were only included if quantitative results were presented by a measure of SEP. Extracted data were categorised with a modified version of the "4Ps" marketing mix, expanded to 6 "Ps": "Price, Place, Product, Prescriptive, Promotion, and Person".


RESULTS
Our search identified 31,887 articles. Following screening, 36 studies were included: 18 "Price" interventions, 6 "Place" interventions, 1 "Product" intervention, zero "Prescriptive" interventions, 4 "Promotion" interventions, and 18 "Person" interventions. "Price" interventions were most effective in groups with lower SEP, and may therefore appear likely to reduce inequalities. All interventions that combined taxes and subsidies consistently decreased inequalities. Conversely, interventions categorised as "Person" had a greater impact with increasing SEP, and may therefore appear likely to reduce inequalities. All four dietary counselling interventions appear likely to widen inequalities. We did not find any "Prescriptive" interventions and only one "Product" intervention that presented differential results and had no impact by SEP. More "Place" interventions were identified and none of these interventions were judged as likely to widen inequalities.


CONCLUSIONS
Interventions categorised by a "6 Ps" framework show differential effects on healthy eating outcomes by SEP. "Upstream" interventions categorised as "Price" appeared to decrease inequalities, and "downstream" "Person" interventions, especially dietary counselling seemed to increase inequalities. However the vast majority of studies identified did not explore differential effects by SEP. Interventions aimed at improving population health should be routinely evaluated for differential socioeconomic impact.
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. rmcgill@liv.ac.uk.
Rory
R
McGill
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. e.anwar@liv.ac.uk.
Elspeth
E
Anwar
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. lorton@liv.ac.uk.
Lois
L
Orton
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. bromley@liv.ac.uk.
Helen
H
Bromley
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. ffionlw@liverpool.ac.uk.
Ffion
F
Lloyd-Williams
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. moflaher@liverpool.ac.uk.
Martin
M
O'Flaherty
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. dctr@exchange.liv.ac.uk.
David
D
Taylor-Robinson
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. mdlgc106@liverpool.ac.uk.
Maria
M
Guzman-Castillo
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. duncan.gillespie@sheffield.ac.uk.
Duncan
D
Gillespie
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. patriciamoreira1111@hotmail.com.
Patricia
P
Moreira
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. allenk@liverpool.ac.uk.
Kirk
K
Allen
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. hysen001@liverpool.ac.uk.
Lirije
L
Hyseni
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. Nicola.calder@hegroup.co.uk.
Nicola
N
Calder
Public and Environmental Health Research Unit, London School of Hygiene and Tropical Medicine, Liverpool, UK. mark.petticrew@lshtm.ac.uk.
Mark
M
Petticrew
UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge, UK. Martin.White@mrc-epid.cam.ac.uk.|Institute of Health and Society, Newcastle University, Newcastle upon Tyne, UK. Martin.White@mrc-epid.cam.ac.uk.
Martin
M
White
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. mmw@liverpool.ac.uk.
Margaret
M
Whitehead
Department of Public Health and Policy, University of Liverpool, Liverpool, UK. capewell@liverpool.ac.uk.
Simon
S
Capewell
D003132:Commerce; D004032:Diet; D005247:Feeding Behavior; D006266:Health Education / Q000458:organization & administration*; D006293:Health Promotion / Q000458:organization & administration*; D006801:Humans; D040541:Marketing / Q000458:organization & administration*; D012959:Socioeconomic Factors; D014675:Vegetables