Reduced away-from-home food expenditure and better nutrition knowledge and belief can improve quality of dietary intake among US adults

Objective: To test whether reduced away-from-home food expenditure (AFHFE) and better nutrition knowledge and beliefs (NKB) are associated with dietary quality among US adults. Design and subjects: The dietary intake data (average of two 24 h recalls) used were collected from US adults (20-65 years) participating in two cross-sectional surveys, the 1994-96 Continuing Survey of Food Intake by Individuals (CSFII; n 7148) and the CSFII/Diet and Health Knowledge Survey (DHKS; n 4252). Outcome measures: Dietary quality was assessed using selected nutrients and food groups and the 2005 revised US Department of Agriculture Healthy Eating Index (HEI). Exposure variables: (i) Absolute AFHFE (weekly, per capita) and proportion of this exposure out of total food expenditure (relative expenditure); (ii) NKB score using a composite of an eleven-item scale elicited among the CSFII/DHKS subgroup. Statistical analyses performed: We used t tests, χ² tests, Wilcoxon rank-sum tests and multivariate linear regression models adjusting standard errors for sample design complexity. We utilized a change-in-estimate approach to assess mediation. For effect modification, we tested the significance of interaction terms (NKB X AFHFE). Results: Absolute AFHFE was positively associated with grams of fat (β = 0.14 (SE 0.06)) and saturated fat (β = 0.02 (SE 0.01)) and negatively associated with fibre (β = -0.02 (SE 0.01)) and HEI (β = -0.08 (SE 0.01)). Relative AFHFE mediated NKB effects on intakes such as fat, saturated fat, cholesterol, Na, and fruits and vegetables (change in estimate >10 %). Among subjects with a poor NKB score, higher AFHFE resulted in lower diet quality, particularly Na and cholesterol intakes. Conclusions: Higher AFHFE was associated with a lower dietary quality and interacted antagonistically with NKB in some instances, while mediating the relationship between NKB and dietary quality in others.