The study, published in the American Journal of Public Health, added food labels in traffic light colors to foods and beverages in a large hospital cafeteria, with red, yellow and green colors reflecting the relative healthiness of different foods and drinks. Signs in the cafeteria encouraged patrons to choose green items often, yellow less often, and to consider alternative choices for red-labeled items.
“Reading and understanding nutrition labels is a complex task,” the researchers wrote. “Even highly literate consumers may have difficulty interpreting labels because of low numeracy skills…Although this scheme provided the consumer with less precise information than does calorie labeling, it conveyed complex information in a way that could be easily understood and acted on immediately.”
Three months after the color scheme was introduced, the effect was most striking for beverage sales, with sales of red-labeled drinks down 16.5% and green beverage sales up 9.6%. Sales of all red items fell 9.2% and green item sales were up 4.5%.
"We found that labeling all foods and beverages with a simple red, yellow and green color scheme to indicate their relative healthiness led patrons to purchase more of the healthy and fewer of the unhealthy items," said lead researcher Anne Thorndike of the MGH division of General Medicine, and assistant professor of medicine at Harvard Medical School. "…We believe this intervention was so successful because it was simple and easy to understand quickly. The labeling did not require any special skills and could be easily interpreted when a customer was in a rush.”
In a second phase of the study, the researchers rearranged the placement of items on shelves and in refrigerators so that the green items were at eye level.
During this phase, red item sales dropped another 4.9% compared with the first phase. Beverage sales fell another 11.4%, and although green item sales fell 0/8% in phase two, sales of green-labeled drinks increased another 4%, the researchers found.
Source: American Journal of Public Health
Published online ahead of print
“A 2-Phase Labeling and Choice Architecture Intervention to Improve Healthy Food and Beverage Choices”
Authors: Anne Thorndike, Lillian Sonnenberg, Jason Riis, Susan Barraclough, and Douglas Levy.