A study carried out by health economists suggests that a little peer influence can motivate us to make healthier grocery choices.
Given the increasing prevalence of chronic illnesses like heart disease and diabetes, new research from Duke-NUS Medical School presents an innovative approach to promote healthier grocery shopping. Although color-coded nutrition labels on packaging aim to guide consumers toward better choices, these efforts have not halted the rise of chronic disease rates.
The research team from Duke-NUS’ Health Services and Systems Research Programme launched a randomized trial to evaluate whether behavioral nudges and financial incentives could enhance dietary quality. The trial utilized NUSMart, a controlled online grocery store.
In the experiment, participants were instructed to complete three separate online shopping sessions, spending approximately S$60 each time. Each visit featured one of three variations of the NUSMart platform:
- A control store where packaged items were displayed with no nutritional information;
- A version showing nutritional labels on each item via a color-coded system, along with a comparative quality meter that benchmarked their shopping basket against peers (peer influence); and
- A variant with both the nutritional labels and peer influence, plus an opportunity to earn a S$5 cash incentive if their shopping basket was healthier than those of their peers at checkout.
The results, which appeared in the journal Food Policy in May, were summarized by first author and Assistant Professor Soye Shin of the Duke-NUS Health Services and Systems Research Programme, who stated:
“Our analysis showed that exposing shoppers to nutritional labels and peer influence significantly improved the healthfulness of their grocery baskets. The addition of the cash incentive provided a further enhancement, but the primary benefit came from the peer influence factor.”
Enhancing the Effectiveness of Nutritional Labels
In this study, the Duke-NUS team implemented the Nutri-Score labeling method, commonly used in several European nations, to inform consumers about nutritional content. This system rates products with letter grades from A (healthiest, green) to E (least healthy, red) based on overall nutrient quality, including sugar, sodium, saturated fats, and calories per serving.
Using the letter grades, the researchers assigned point scores from 5 points for an A to 1 point for an E to assess the healthiness of the grocery basket; a higher score indicated a healthier selection.
When participants were able to see the nutritional labels and compare their shopping baskets with peers, there was a 14 percent improvement in dietary quality compared to the control group.
Introducing the cash incentive in a “loss-frame” approach (emphasizing the reward as “yours to lose”) led to an additional 5.6 percent improvement in dietary quality. Overall, the combined strategies shifted the average nutritional quality from a low C grade to a low B grade.
Even without the incentive, the improvements were significant enough to promote better health outcomes. The introduction of front-of-pack labels along with peer influence reduced average sugar purchases by 8.9 grams per serving. A 2022 survey from the Singapore Health Promotion Board (HPB) indicated that Singaporeans consume 6 grams more than the recommended daily maximum for sugar. Cutting down sugar intake by 8.9 grams per serving could greatly aid efforts against diabetes, the researchers noted.
A similar trend was observed concerning sodium, with participants choosing products that contained, on average, 3.7 grams less per serving. Such a reduction could be particularly beneficial for the 90 percent of Singaporeans, according to HPB data, who consume 3.6 grams above the recommended daily limit of 2.0 grams.
Senior author Professor Eric Finkelstein from the Duke-NUS Health Services and Systems Research Programme commented:
“We’ve seen peer influence effectively reduce energy intake. Our findings now show that it can also drive consumers towards healthier selection. This approach is simple and cost-effective in combating chronic diseases. I hope these insights encourage supermarkets to integrate these strategies into their online shopping experiences.”
Professor Patrick Tan, Senior Vice-Dean for Research at Duke-NUS, remarked on the potential significance of their work, saying:
“These findings are incredibly relevant right now. The COVID pandemic has significantly altered grocery shopping behaviors, with a surge in online shopping. This shift presents a unique opportunity to apply innovative solutions that help consumers enhance their diets, which is crucial in our battle against non-communicable diseases like diabetes and cardiovascular issues.”
Duke-NUS is at the forefront of medical research and innovation, committed to elevating patient care through systems research and scientific exploration. This study is part of the institution’s ongoing initiatives to promote national policies for healthy living and longer life.
