Pressure-Mediated Reflection Spectroscopy Criterion Validity as a Biomarker of Fruit and Vegetable Intake: A Two-Site Cross-Sectional Study of Four Racial Or Ethnic Groups.

Background Valid biomarkers of fruit and vegetable (FV) intake are needed for field-based nutrition research. Objective To examine criterion-related validity of pressure-mediated reflection spectroscopy as a proxy measure of FV intake, using plasma carotenoids and self-reported FV and carotenoid intake as primary and secondary criterion measures, respectively. Methods Healthy adults 18-65 years of age, self-identifying as African American/ black (n = 61), Asian (n = 53), white (n = 70), or Hispanic (n = 29) in North Carolina and Minnesota were recruited. Skin carotenoids were assessed via pressure-mediated reflection spectroscopy (Veggie Meter ®), skin melanin via spectrophotometer, and total plasma carotenoid concentration by HPLC-PDA. Self-reported carotenoid and FV intake was assessed using a semi-quantitative food frequency questionnaire. Relationships between skin carotenoids, plasma carotenoids, FV and carotenoid intake, with differences by race or ethnicity, age, sex, weight status, cholesterol, and melanin index, were examined by bivariate correlations and adjusted multivariate linear regressions. Results The overall unadjusted correlation between skin and total plasma carotenoids was r = 0.71 and ranged from 0.64 (non-Hispanic black) to 0.80 (Hispanic). Correlations between skin carotenoids and self-reported FV intake ranged from 0.24 (non-Hispanic black) to 0.53 (non-Hispanic white), with an overall correlation of r = 0.35. In models adjusted for age, sex, racial or ethnic group, and body mass index, skin carotenoids were associated with plasma carotenoids (R2 = 0.55), FV (R2 = 0.17), and carotenoid intake (R2 = 0.20). For both plasma carotenoid and FV measures, associations with skin carotenoids did not vary by race; but these relationships did differ by skin melanin - those with lower melanin had a lower correlation between skin and plasma carotenoids. Conclusions Reflection spectroscopy-assessed skin carotenoids may be a reasonable alternative to measurement of plasma carotenoids, a biomarker used to approximate FV intake.