Background: Diet is an important risk factor for cardiovascular disease and shows well-established socioeconomic patterning among adults. However, less clear is how socioeconomic inequalities in diet develop across the life course. This study assessed the associations of early adulthood socioeconomic trajectories (SETs) with adult diet quality, adjusting for childhood socioeconomic position (SEP) and testing for mediation by adulthood SEP.

Methods: Participants from the 1970 British Cohort Study with socioeconomic data in early adulthood were included (n=12,434). Diet quality at age 46 years, evaluated using the Mediterranean diet pyramid, was regressed on six previously identified classes of early adulthood SETs between ages 16 and 24 years, including a Continued Education class, four occupation-defined classes, and an Economically Inactive class. Causal mediation analyses tested the mediation of the association via household income and neighbourhood deprivation at age 46 years separately. Models were adjusted for sex, childhood SEP, adolescent diet quality and adolescent health.

Results: The Continued Education class showed the best diet quality at age 46 years, while little difference in diet quality was found among the remaining SET classes. The association between the Continued Education class and adult diet quality was independent of parental SEP in childhood, and was largely not mediated by household income or neighbourhood deprivation (0.7% and 3.7% of the total effect mediated, respectively) in mid-adulthood.

Conclusions: Early adulthood SETs independently contribute to adult diet quality, with continuing education associated with better adherence to Mediterranean diet. Early adulthood therefore represents a sensitive period for intervention to alleviate dietary inequalities in later life.