Are food and drink available in online and physical supermarkets the same? A comparison of product availability, price, price promotions and nutritional information

Objective: Online supermarkets are increasingly used both by consumers and as a source of data on the food environment. We compared product availability, nutritional information, front-of-pack (FOP) labelling, price and price promotions for food and drink products between physical and online supermarkets. Design: For physical stores, we collected data on price, price promotions, FOP nutrition labels and nutrition information from a random sample of food and drinks from six UK supermarkets. For online stores, we used foodDB, a research-ready dataset of over 14 million observations of food and drink products available in online supermarkets. Setting: Six large supermarket stores located near Oxford, UK. Participants: General sample with 295 food and drink products, plus boost samples for both fruit and vegetables, and alcohol. Results: In the general sample, 85 % (95 % CI 80, 90 %) of products found in physical stores could be matched with an online product. Nutritional information found in the two settings was almost identical, for example, concordance correlation coefficient for energy = 0.995 (95 % CI 0.993, 0.996). The presence of FOP labelling and price promotions differed between the two settings (Cohen's kappa = 0.56 (95 % CI 0.45, 0.66) and 0.40 (95 % CI 0.26, 0.55), respectively). Prices were similar between online and physical supermarkets (concordance correlation coefficient > 0.9 for all samples). Conclusions: Product availability, nutritional information and prices sourced online for these six retailers are good proxies of those found in physical stores. Price promotions and FOP labelling vary between the two settings. Further research should investigate whether this could impact on health inequalities.