October 2, 2019

A randomized controlled trial from the UNC Gillings School of Global Public Health finds that even brief exposure to health warnings on sugar-sweetened beverages reduced purchases of those beverages, providing evidence that such warnings promote healthier drink choices.

Dr. Anna Grummon

Dr. Anna Grummon

Anna Grummon, PhD, a recent doctoral graduate of the School’s health behavior department, is lead author of “Sugar-Sweetened Beverage Health Warnings and Purchases: A Randomized Controlled Trial,” which was published online October 2 by the American Journal of Preventive Medicine.

Poor diet contributes to chronic health conditions such as obesity and diabetes. As such, policymakers are eyeing strategies that will keep their communities healthy. Lawmakers in California, New York, Vermont and other states have proposed policies to require health warnings on sugary drinks like sodas, sports drinks and sweetened tea, but there has been limited research on whether such warnings would change what consumers buy.

Previous studies examined how consumers respond to images of warnings on computer screens; Grummon’s study is unique in examining how health warnings influence what consumers actually buy in real settings.

“Our study is one of the first to look at warnings in a more real-world context,” says Grummon. “We worked in a convenience-store laboratory that allowed us to control whether the sugary drinks had warnings. We are also one of the first studies to measure what consumers actually buy after seeing warnings, when they have their own money on the line.”

The researchers used electronic and print recruitment tools to screen and enroll 400 adult consumers of sugary beverages in the study. Participants in the study’s control arm purchased an average of about 143 calories (about a soda can’s worth) from sugary beverages in the form of sodas, fruit drinks, energy drinks and sweetened tea. Participants in the health warning arm purchased only about 110 calories from sugary beverages. The study also found that the warnings were influential across diverse groups: The effect of health warnings on beverage purchases did not differ by participants’ race/ethnicity, education, age, gender, income, body weight or health-literacy level.

These results should clarify for policymakers that warning labels on sugary drinks would be effective in promoting healthier choices, says Grummon.

“We found that participants who saw the health warning labels purchased about 22% fewer calories from sugary drinks compared to participants who saw a neutral label that looked like a barcode,” she says. “This is important evidence, because it suggests that health warnings can help consumers make healthier choices about which drinks to buy.”

According to Grummon, critics of health warning labels argue that consumers won’t notice or pay attention to the warnings. However, three-quarters of the participants in this study reported noticing the health warnings, and most of those participants also reported that they read and looked closely at the labels.

Consumers should have the information they need to make informed choices about what they eat and drink, she says.

“In our study, participants exposed to health warning labels reported that they thought more about the harms of consuming sugary drinks than participants who saw control labels,” Grummon states. “This is one important way that warnings promote informed decisions: Warnings help consumers keep the health consequences of sugary drinks at top of mind while they’re deciding what to buy.”

Other study authors from the Gillings School include Lindsey Smith Taillie, PhD, assistant professor of nutrition; Shelley Golden, PhD, assistant professor of health behavior; Marissa G. Hall, PhD, assistant professor of health behavior; and Noel Brewer, PhD, professor of health behavior and the study’s senior author. Hall and Brewer are members of the UNC Lineberger Comprehensive Cancer Center.

When asked about next steps, Smith Taillie shared an ongoing research study: “We are expanding on the success of this study by developing and testing the UNC Mini Mart, a new and larger ‘convenience store lab.’ In this even more realistic setting, we are able to sell full-sized products instead of only single-serving drinks. That has enabled us to conduct our current pilot study, which examines the impact of both warning labels and taxation for sugar-sweetened beverages on what 60 Latinx families consume during a five-week study.”

In the future, Gillings School researchers plan to use the innovative lab space to study a wide range of health behavior policies meant to be implemented at the point of sale — including graphic warning labels on tobacco products.

“Good warnings scare people. That’s the point,” says Brewer. “Feelings add meaning to facts, helping people take back control of their health. Our previous research has shown that cigarette pack warnings help smokers quit. Now we know that warnings for sugar-sweetened beverages also help consumers make healthier choices.”


Contact the Gillings School of Global Public Health communications team at sphcomm@unc.edu.

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