Poster Topical Area: Nutritional Epidemiology
Location: Hall D
Poster Board Number: 809
Objective: Intervention studies targeting diet quality typically rely on self-reported intake. However, intervention participation may influence dietary self-report, either by increasing social desirability bias (leading to greater misreporting) or by increasing attention to intake, thereby improving recall and portion estimation. Such differential reporting bias would impair estimates of treatment effect; however, few studies have tested this empirically. This study examined differential response bias by examining the relationship of fruit and vegetable (FV) intake with serum carotenoids among youth with type 1 diabetes participating in a randomized controlled behavioral nutrition intervention trial targeting increased whole plant food intake.
Methods: Participants (n=136) completed 3-day food records at baseline, 6-,12-, and 18-months, from which FV intake (servings/day) was calculated. Serum carotenoids were assessed at these visits using a high-performance liquid chromatography-based assay. Linear regression estimated associations of FV intake with serum carotenoids by treatment assignment, adjusting for glycemic control and sociodemographic characteristics. Multiplicative interaction terms tested the interaction of treatment assignment with FV intake on serum carotenoids for each visit and within each group over time.
Results: The association of FV intake with serum carotenoids was lower in the control versus intervention group, with a significant interaction effect observed for baseline (β=-0.49, p=0.04) and 6-month (β=-0.57, p=0.03) visits. However, the association of FV intake with serum carotenoids did not significantly differ over time for either group.
Conclusions: While the stronger association of FV with carotenoids in the intervention group suggests differential reporting bias indicating greater reporting accuracy among intervention participants, this difference was evident at baseline, and did not change significantly over time in either group. Thus, findings do not provide evidence for reactivity to the intervention in reporting of dietary intake.
Eunice Kennedy Shriver National Institute of Child Health and Human Development