Impact of health warning labels on selection and consumption of food and alcohol products: systematic review with meta-analysis.

Health warning labels (HWLs) could reduce harmful consumption of food (including non-alcoholic drinks) and alcoholic drinks. A systematic review with meta-analysis using Cochrane methods was conducted to assess the impact on selection (including hypothetical selection) or consumption of food or alcoholic drink products displaying image-and-text (sometimes termed 'pictorial') and text-only HWLs. Fourteen randomised controlled trials were included, three for alcohol, eleven for food. For the primary outcomes, eleven studies measured selection and one measured consumption (two measured only other secondary outcomes). Meta-analysis of twelve comparisons from nine studies (n=12,635) found HWLs reduced selection of the targeted product compared with no HWL (RR=0.74 (95%CI 0.68-0.80)), with participants 26% less likely to choose a product displaying a HWL. A planned subgroup analysis suggested a larger (although not statistically significant) effect on selection of image-and-text HWLs (RR=0.65 (95%CI 0.54-0.80)) than text-only HWLs (RR=0.79 (95%CI 0.74-0.85)). These findings suggest significant potential for HWLs to reduce selection of food and alcoholic drinks, but all experimental studies to date were conducted in laboratory or online settings with outcomes assessed immediately after a single exposure. Studies in field and naturalistic laboratory settings are needed to estimate the potential effects of food and alcohol HWLs. PROSPERO 2018 (registration number: CRD42018106522)