Joanna Cosgrove03.18.10
In a time when many consumers have found themselves forfeiting healthy food choices in lieu of cheaper food choices, researchers in New Zealand have confirmed that promoting healthy eating habits would be far more successful if price discounts were coupled with nutritional education.
“Poor diet is one of the most important health issues facing developed countries such as New Zealand,” commented Dr. Cliona Ni Mhurchu, programme leader at the Nutrition & Physical Activity Clinical Trials Research Unit of the University of Auckland in New Zealand. “Rates of obesity and overweight are steadily increasing, and poor dietary habits are responsible for up to 40% of deaths in this country, or around 11,000 deaths each year.”
It’s important, she said, to find effective ways to encourage people to buy and eat healthier foods beyond simply relying on personal responsibility, possibly via more structural interventions such as pricing policies. “Traditionally there has been reliance on nutrition education to promote healthier diets. Targeted pricing options such as taxes and price discounts have also been debated but until now estimates of effect have been based largely on theoretical models,” she said.
To that end, Dr. Ni Mhurchu and her University of Auckland colleagues set out to test the effects of price reduction on healthier foods in a real-life setting. The team conducted a randomized controlled trial that was carried out in eight New Zealand supermarkets. A total of 1104 shoppers were recruited to randomly receive 12.5% price discounts on healthier foods (as recognized by New Zealand’s Heart Foundation), nutrition education (in the form of food-group-specific information tailored to their shopping history), food discounts plus education, or no intervention at all. Handheld barcode scanners recorded all supermarket purchases for six months.
According to results of the study, which were published in the American Journal of Clinical Nutrition, at the end of the sixth month, those who received price discounts bought about 1.7 more pounds (0.79 kg) of healthy food per week compared to those who paid full price.
This was an 11% increase from purchases made prior to the study and included just over a pound (.48 kg) more fruits and vegetables per week, or about six servings. The total difference dropped to around 0.8 pounds (.38 kg), but remained significant, six months after the study’s conclusion. Neither price discounts nor tailored nutrition education had a significant effect on saturated fat purchases.
The fact that nutrition education was unsuccessful in improving food choices initially surprised Dr. Ni Mhurchu, especially since previous research had shown positive effects. Most of those studies, however, used self-report rather than the more objective supermarket sales data. Still, she said, her study participants were generally more informed and interested in healthy eating than average individuals, which could have masked education's true impact.
“We were also disappointed that the clear impact of price discounts on the types of food purchased did not translate to significant changes in nutrients such as saturated fat, sugar, or sodium,” commented Dr. Ni Mhurchu. “The modest increase in purchases of healthier foods (11%) combined with the relatively small proportion of food that fell within this category (35% of all products), may account for this.”
The study, believed to be the first of its kind to test the effects of price reduction on healthier foods in a real-life setting, is just the beginning of Dr. Ni Mhurchu and her team’s efforts. Later this year they plan to begin another intervention that will examine the effects of more targeted price incentives (e.g., cash back or voucher rewards) on fruit and vegetable purchases and consumption by priority ethnic and low-income families. For this study, 510 families will be randomized to price incentive or control groups. The burden of nutrition-related disease and inequalities among these priority populations warrants more targeted approaches.