The effect of social norms messaging regarding skin carotenoid concentrations among college students

Descriptive social-normative messaging positively influences short-term dietary choices and healthy food intake. The purpose of this study was to evaluate the effects of descriptive normative messages on college students' skin carotenoid concentrations (a biomarker of carotenoid-containing fruit and vegetable [FV] intake) over an 8-week period. 251 college students consented to participate and 74% completed the study. Students were randomly assigned to groups who, following a baseline evaluation of skin-carotenoid levels, were told how their score ranked within a peer group of college students attending the same university (Individualized Normative group), that their score was in the lower 20th percentile of the peer group (Manipulated Normative group), or were given no information about their score or the peer group (Control group). Skin carotenoid concentrations were reassessed 8 weeks after the normative messages were presented or withheld. Skin carotenoid levels of those in the Manipulated Normative group increased significantly more than did scores of those in the Control group (t (126) = 3.74, p < 0.001; d = 0.67), but these students' self-reported FV intake did not increase. This finding suggests normative messaging can influence behavior for up to 8 weeks, but future research must better evaluate if the increase in skin carotenoids reflects increased FV consumption, increased consumption of carotenoid-containing FV (with decreased consumption of other FV), or is accounted for by some other behavior change (e.g., increased use of supplements). These findings support further exploration of normative messaging as a technique for producing the long-term behavior change needed to impact public health.