Background To date, the evaluation of diet has mostly been based on questionnaires and diaries that have their limitations in terms of being time and resource intensive, and a tendency toward social desirability. Loyalty card data obtained in retailing provides timely and objective information on diet-related behaviors. In Finland, the market is highly concentrated, which provides a unique opportunity to investigate diet through grocery purchases. Objective The aims of this study were as follows: (1) to investigate and quantify the selection bias in large-scale (n=47,066) loyalty card (LoCard) data and correct the bias by developing weighting schemes and (2) to investigate how the degree of loyalty relates to food purchases. Methods Members of a loyalty card program from a large retailer in Finland were contacted via email and invited to take part in the study, which involved consenting to the release of their grocery purchase data for research purposes. Participants’ sociodemographic background was obtained through a web-based questionnaire and was compared to that of the general Finnish adult population obtained via Statistics Finland. To match the distributions of sociodemographic variables, poststratification weights were constructed by using the raking method. The degree of loyalty was self-estimated on a 5-point rating scale. Results On comparing our study sample with the general Finnish adult population, in our sample, there were more women (65.25%, 30,696/47,045 vs 51.12%, 2,273,139/4,446,869), individuals with higher education (56.91%, 20,684/36,348 vs 32.21%, 1,432,276/4,446,869), and employed individuals (60.53%, 22,086/36,487 vs 52.35%, 2,327,730/4,446,869). Additionally, in our sample, there was underrepresentation of individuals aged under 30 years (14.44%, 6,791/47,045 vs 18.04%, 802,295/4,446,869) and over 70 years (7.94%, 3,735/47,045 vs 18.20%, 809,317/4,446,869), as well as retired individuals (23.51%, 8,578/36,487 vs 31.82%, 1,414,785/4,446,869). Food purchases differed by the degree of loyalty, with higher shares of vegetable, red meat & processed meat, and fat spread purchases in the higher loyalty groups. Conclusions Individuals who consented to the use of their loyalty card data for research purposes tended to diverge from the general Finnish adult population. However, the high volume of data enabled the inclusion of sociodemographically diverse subgroups and successful correction of the differences found in the distributions of sociodemographic variables. In addition, it seems that food purchases differ according to the degree of loyalty, which should be taken into account when researching loyalty card data. Despite the limitations, loyalty card data provide a cost-effective approach to reach large groups of people, including hard-to-reach population subgroups.

The validity of grocery purchase data as an indicator of food consumption is uncertain. This paper investigated 1) the associations between food consumption and grocery purchases using automatically accumulated purchase data, and 2) whether the strength of the associations differed in certain sub-populations. The participants filled in a food frequency questionnaire (FFQ), and a major Finnish retailer issued us with their loyalty-card holders grocery purchase data covering the 1- and 12-month periods preceding the FFQ. We used gamma statistics to study the association between thirds/quarters of FFQ and grocery purchase data (frequency/amount) separately for 18 food groups among the 11,983 participants. Stratified analyses were conducted for subgroups based on gender, family structure, educational level, household income and self-estimated share of purchases from the retailer. We also examined the proportion of participants classified into the same, adjacent, subsequent and opposite categories using the FFQ and purchase data. The gammas ranged from 0.12 (cooked vegetables) to 0.75 (margarines). Single households had stronger gammas than two-adult families, and participants with >60% of purchases from the retailer had stronger gammas. For most food groups, the proportion of participants classified into the same or adjacent category was >70%. Most discrepancies were observed for fresh/cooked vegetables, berries, and vegetable oils. Even though the two methods did not categorize all food groups similarly, we conclude that grocery purchase data are able to describe food consumption in an adult population, and future studies should consider purchase data as a resource-saving and moderately valid measure in large samples.

Achieving a sustainable and healthy diet requires increased replacement of red meat with more sustainable foods. There is a call for novel methodologies to assess the potential of different interventions and policies in enhancing the transition from the current to more sustainable choices. We aimed to characterize consumer clusters with similar preferences in protein sources, to compare the purchase prices of these foods, and to identify ongoing transitions from one protein source to another. Grocery purchase data with individual attributes on 29,437 consenting loyalty card holders were analyzed over 2.3 year period. We designed a sequence analysis to group participants to clusters with similar purchase preferences over the follow-up period and to estimate transition probabilities between preferences. We studied the determinants of prevalent purchase profiles by ordinal logistic models. We identified six participant profiles with similar preferences in four protein sources: red meat, poultry, fish, and plant-based foods. Red meat dominated the purchase preferences and showed the highest persistence over time. The majority (70%) of the participants demonstrated somewhat mixed purchase profiles. A step-by-step transition from red meat towards plant-based food preference seems most likely via poultry and fish. Overall, low income was not a barrier to a more sustainable purchase profile, while price may deter the purchase of fish. The most important resources in choosing more sustainable profiles were education and stage of family life. Societal incentives for sustainable food choices seem most crucial at transition stages of life course and for the less educated. Here, we also demonstrate that grocery purchase data offer a valuable tool for monitoring the progressive transition towards a healthy and sustainable food system.

Our observations of the Finnish CF mutation spectrum fit well with the characteristics of Finland as a population of multiple local founder effects.

Objective: To identify food purchase patterns, and to assess their carbon footprint and expenditure. Design: Cross-sectional. Setting: Purchase patterns were identified by factor analysis from the annual purchases of 3435 product groups. The associations between purchase patterns and the total purchases’ carbon footprints (based on life-cycle assessment) and expenditure were analyzed using linear regression and adjusted for nutritional energy content of the purchases. Participants: Loyalty card holders (n=22,860) of the largest food retailer in Finland. Results: Eight patterns explained 55% of the variation in food purchases. The Animal-based pattern made the greatest contribution to the annual carbon footprint, followed by the Easy-cooking, and Ready-to-eat patterns. High-energy, Traditional, and Plant-based patterns made the smallest contribution to the carbon footprint of the purchases. Animal-based, Ready-to-eat, Plant-based, and High-energy patterns made the greatest contribution whereas the Traditional, and Easy-cooking pattern made the smallest contribution to food expenditure. Carbon footprint per euros spent increased with stronger adherence to the Traditional, Animals-based, and Easy-cooking patterns. Conclusions: The Animal-based, Ready-to-eat, and High-energy patterns were associated with relatively high expenditure on food, suggesting no economic barrier to a potential shift towards a plant-based diet for consumers adherent to those patterns. Strong adherence to the Traditional pattern resulted in a low energy-adjusted carbon footprint but high carbon footprint per euro. This suggests a preference for cheap nutritional energy rather than environment-conscious purchase behavior. Whether a shift towards a plant-based pattern would be affordable for those with more traditional and cheaper purchase patterns requires more research.