Effects of price discounts and tailored nutrition education on supermarket purchases: a randomized controlled trial12345

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Background: Traditional methods to improve population diets have largely relied on individual responsibility, but there is growing interest in structural interventions such as pricing policies.

Objective: The aim was to evaluate the effect of price discounts and tailored nutrition education on supermarket food and nutrient purchases.

Design: A 2 × 2 factorial randomized controlled trial was conducted in 8 New Zealand supermarkets. A total of 1104 shoppers were randomly assigned to 1 of the following 4 interventions that were delivered over 6 mo: price discounts (12.5%) on healthier foods, tailored nutrition education, discounts plus education, or control (no intervention). The primary outcome was change in saturated fat purchased at 6 mo. Secondary outcomes were changes in other nutrients and foods purchased at 6 and 12 mo. Outcomes were assessed by using electronic scanner sales data.

Results: At 6 mo, the difference in saturated fat purchased for price discounts on healthier foods compared with that purchased for no discount on healthier foods was −0.02% (95% CI: −0.40%, 0.36%; P = 0.91). The corresponding difference for tailored nutrition education compared with that for no education was −0.09% (95% CI: −0.47%, 0.30%; P = 0.66). However, those subjects who were randomly assigned to receive price discounts bought significantly more predefined healthier foods at 6 mo (11% more; mean difference: 0.79 kg/wk; 95% CI: 0.43, 1.16; P < 0.001) and 12 mo (5% more; mean difference: 0.38 kg/wk; 95% CI: 0.01, 0.76; P = 0.045). Education had no effect on food purchases.

Conclusions: Neither price discounts nor tailored nutrition education had a significant effect on nutrients purchased. However, the significant and sustained effect of discounts on food purchases suggests that pricing strategies hold promise as a means to improve population diets.

Cited by (0)

1

From the Clinical Trials Research Unit, School of Population Health, The University of Auckland, Auckland, New Zealand (CNM, YJ, and HCE); MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, United Kingdom (CNM); the Department of Public Health, University of Otago, Wellington, Wellington South, New Zealand (TB); and the George Institute of International Health, Sydney, Australia (AR).

2

The SHOP trial results were presented at the International Society of Behavioral Nutrition and Physical Activity Annual Meeting in Cascais, Portugal, 17–20 June 2009.

3

The funding organizations had no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; or preparation, review, or approval of the manuscript.

4

Supported by the Health Research Council of New Zealand (06/379). CNM holds the Heart Foundation Senior Fellowship (grant no. 1380). HCE holds a Heart Foundation Postgraduate Scholarship (grant no. 1285).

5

Address correspondence to C Ni Mhurchu, Clinical Trials Research Unit, School of Population Health, University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland 1142, New Zealand. E-mail: [email protected].