Construct Validity of a Single-Item, Self-Rated Question of Diet Quality

ObjectiveTo provide evidence of the construct validity of a single-item overall diet question with a nomological network of self-rated and biometric measures of dietary intake and outcomes.MethodsThe authors conducted a secondary analysis of survey and biometric data from a cross-sectional sample of urban-dwelling adults. In addition to self-rated diet quality, they examined dietary behaviors, biomarkers of intake, and related outcomes. Self-rated diet quality was treated as a continuous variable to calculate P for trend using regression analysis.ResultsSelf-rated diet quality was significantly associated with variation in both subjective and objective measures of dietary intake (fruit and vegetable intake, P < .001; sugar-sweetened beverage intake, P < .001; sodium to potassium ratio, P < .001), behavior (frequency of fast-food dining, P < .001), and related outcomes (systolic blood pressure, P = .010; diastolic blood pressure, P < .001; and body mass index, P < .001).Conclusions and ImplicationsEvidence supports the construct validity of a single-item measure of diet quality. This single-item question may be a useful proxy for more burdensome measures of overall diet quality.