The network meta-analysis summarised the current available 134 studies, nested in 120 peer-reviewed articles, to update the knowledge of the most mainstream 'interpretive' front-of-pack nutrition labelling schemes (i.e. those that use colours, symbols or graphics to aid consumers in understanding nutrition information).
It found that the UK's Traffic-light Labelling System (TLS), Nutri-Score (NS), Chile-style Nutrient Warning labels (NW) and Health Warnings (HW)2 - all examples of interpretive front-of-pack labelling - were all able to direct consumers towards more healthy purchases, reducing the energy, salt, fat or saturated fat content of processed foods and drinks chosen or purchased.
Lead author Dr Jing Song, Postdoctoral Research Fellow at Queen Mary University of London, said: "Despite the variation in label types, labelling formats, position, study population, study design and experimental settings across studies, our comprehensive systematic review and meta-analysis supports the call for colour coded front-of-pack nutrition labels, which all have positive effects on guiding consumers in making more healthful food choices. Food manufacturers must now get on board in efforts to improve the nation's health by committing to putting front-of-pack labels across all their food and drink products and on menus."
New evidence
Prior to this study, evidence on the impact of each type of colour-coded label and warning labels on modifying consumers purchasing behaviours was mixed. This research demonstrates that all interpretive nutrition labels support consumers, but curiously, colour-coded labels (TLS and NS) perform better in highlighting positive aspects of products and encourage consumers to purchase healthier products. In contrast, warning labels (NW and HW) put the negative aspects of products front and centre which discourages the purchase of less healthy products.
Interpretive front-of-pack labelling is considered a cost-effective strategy to promote a more healthful diet and prevent diet-related disease. The UK's Traffic-light Labelling System has been in place in its current format since 2013, displaying levels of total fat, saturated fat, total sugar and salt in products colour-coded as either high (red), medium (amber) or low (green). While many UK food companies now display these labels, since it is a voluntary scheme around one in four products does not display them4. Colour-coded labelling is not present in the out of home sector either (i.e. restaurants, cafes, fast food outlets).
In 2020, the UK Government consulted on front of pack nutrition labels, inviting views on the current Traffic-light Labelling System and a potential move to Nutri-Score or Chile-style Nutrient Warning Labels. However, this study, published in PLOS Medicine, found that much of the existing research on nutrition labels focuses on short term computer simulations. This research suggests future studies should focus on the real-world impact of nutrition labels on individuals' eating patterns, and on industrial reformulation at the population level, over a longer timeframe.
Making labels mandatory
Action on Salt and Sugar recommend that the Government make the UK's current voluntary Traffic-light Labelling System mandatory across all products, including the Out of Home sector, as part of their response to the National Food Strategy. The scheme should be evaluated in real time to assess effectiveness in helping to prevent obesity and diet-related diseases such as stroke, heart attacks and various cancers.
Mhairi Brown, co-author and Policy Manager for Action on Salt and Sugar said: "The Government's recent consultation on front-of-pack nutrition labels invited views on different labelling formats but did not indicate their intention to make labels mandatory. This research provides clear evidence that labelling works. We are now urging the Government to make labelling mandatory across all products as this would force manufacturers to show consumers, at a glance, if the product is healthier or less healthy - and hopefully encourage them to reformulate to reduce levels of salt, sugar and saturated fat."
Professor Graham MacGregor, Chair of Action on Salt and Sugar said: "Policies that encourage food manufacturers to improve what goes into the foods we buy will help improve the nation's diet. Suboptimal diets are a leading risk factor for death and disability and the Covid-19 pandemic has reinforced how vital it is for the Government to break the junk food cycle. The Government must commit to mandatory front of pack nutrition labelling as part of their response to the National Food Strategy - alongside comprehensive and strictly monitored reformulation programmes - to support the nation's health."
More information
- Read the full press release from Action on Salt and Sugar.
- Research publication: Song J, Brown MK, Tan M, MacGregor GA, Webster J, Campbell NRC, et al. (2021) Impact of color-coded and warning nutrition labelling schemes: A systematic review and network meta-analysis. PLoS Med 18(9): e1003765. https://doi.org/10.1371/journal.pmed.1003765
- Related article: Taking Action on Salt: How Queen Mary's research improved the food on your plate
- Related article: Keeping everyone sweet − sugar, childhood obesity and the food industry
