During adolescence, many young people start to make more independent food purchases. Subsequently, these independent food choices will increasingly contribute to their overall diet quality; little is known, however, about this relationship. This study aimed to examine the role adolescents’ independent food purchases play in their diet quality and assess if these relationships vary according to socio-economic status. A convenience sample of adolescents aged 11-18 years and attending secondary school or college in Hampshire, England, were recruited to participate in a one-week cross-sectional observational study. A validated 20-item Food Frequency Questionnaire assessed diet quality. Participants used an ecological momentary assessment mobile phone app to record food purchases. Over seven days, 552 food/drink items were purchased on 253 food purchasing occasions by 80 participants. The majority of purchases (n=329, 60%) were coded as ‘not adhering’ to the UK Eatwell Guide, 32% were coded as ‘adhering’ and 9% fell between these two categories. Healthier food purchasing was associated with better diet quality (β 0.48, (95%CI 0.01, 0.96) p=0.05); results attenuated after adjustment for confounders (β 0.36, (95%CI -0.15, 0.87) p=0.16). Interaction models showed purchasing healthfulness was more strongly associated with diet quality among young people of lower SES (p=0.01). The majority of adolescents’ independent food purchases did not adhere to healthy eating guidelines. For adolescents experiencing socioeconomic disadvantage, these food choices had a more detrimental impact on their overall diet quality than they did for more advantaged adolescents. Future research should focus on identifying ways to support more healthful independent food choices by adolescents to reduce dietary inequalities and improve health and well-being among the next generation of adults.

The authors have declared no competing interest.

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This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving research study participants were approved by the Faculty of Medicine Ethics Committee, University of Southampton (ERGO 57044).

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Due to ethical restrictions imposed in the interest of protecting participant confidentiality, the data underlying this study are available upon request. Researchers wishing to use the data can make apply to the research team by emailing mrcleu@mrc.soton.ac.uk. Subject to approval that the intended purpose is compatible with the study’s ethical approval and formal agreements regarding confidentiality and secure data storage being signed, the data would then be provided.