A diet rich in fruits and vegetables (F\&Vs) is associated with lower risk of nutrition-related chronic diseases and all-cause mortality. Despite these benefits, the US population under-consumes F\&Vs, with particularly low intake in disadvantaged populations. Low F\&V intake results in higher rates of nutrition-related chronic disease among disadvantaged populations when compared with more advantaged populations. Detecting and addressing inadequate F\&V intake in these populations is needed to reduce such disparities. Yet, there is still no commonly used predictive, objective measure of F\&V intake for surveillance or determination of policy or intervention effectiveness. The current objective, "gold standard" marker of F\&V intake is blood carotenoid concentration-an expensive, time-intensive, and invasive measurement. Traditional methods of self-reported dietary assessment are imprecise and have diminished utility in rural and disadvantaged populations due to low literacy, numeracy, and internet connectivity. In the past decade, skin carotenoid status assessed by non-invasive resonance Raman spectroscopy (RRS) has emerged as a promising biomarker of F\&V intake. Reflection spectroscopy (RS) is an improvement over RRS, offering stronger signals, faster data acquisition, and greater portability in a commercially available device (Veggie Meter, Longevity Link Corporation). However, a hurdle impedes use of RS in scientific studies: to date, nearly all of the non-invasive skin carotenoid validation has been conducted in non-Hispanic whites, primarily by RRS. Therefore, it is critical to evaluate RS in racially and ethnically diverse populations. The central goal of this proposal is to examine validity and sensitivity of RS-assessed skin carotenoid status as a marker of F\&V intake in a racially and ethnically diverse sample of individuals. First, the investigators will examine the association (RS Device Validity) between RS-assessed skin carotenoids and the primary outcomes of objectively-measured plasma carotenoids and self-reported F\&V consumption across four diverse groups: African-American/Black, Asian, White, and Hispanic/Latino (target n = 320 but due to Covid-19, N=213). Then the investigators will conduct a randomized controlled trial to define the relative skin carotenoid responses (RS Device Sensitivity) across racial-ethnic groups, in comparison with plasma carotenoid responses. The investigators will conduct an 6-week randomized controlled trial of a carotenoid-containing juice intervention \[placebo control, low and high dose juice across 4 genetically-stratified racial-ethnic groups (goal n = 156). Finally, the genetic basis for racial/ethnic group differences in skin carotenoid responses to diet will be investigated through hypothesis-driven genomic analysis of participants from Aims 1 and 2. The results of this study will prepare RS for mass deployment in population surveillance studies and community-based intervention trials, ultimately leading to more accurate determination of the most effective strategies to reduce health disparities related to low F\&V intake in the United States and beyond.
