Reflection Spectroscopy-Assessed Skin Carotenoids Are Sensitive to Change in Carotenoid Intake in a 6-Week Randomized Controlled Feeding Trial in a Racially/Ethnically Diverse Sample.

BACKGROUND: Reflection spectroscopy, utilized by the Veggie Meter, is a less-expensive, noninvasive method to quantify skin carotenoids and is a valid approximation of fruit and vegetable (FV) intake. However, it is unknown to what degree Veggie Meter-assessed skin carotenoid score change is responsive to changes in carotenoid intake. OBJECTIVES: This study aimed to evaluate Veggie Meter-assessed skin carotenoid score response in a 6-wk randomized controlled trial of a carotenoid-containing juice to determine whether the Veggie Meter can be used to detect nutritionally relevant changes in carotenoid intake; and to compare skin and plasma carotenoid responses with the 6-wk trial. METHODS: In this 6-wk trial, participants (n = 162) who self-identified as one of 4 US racial/ethnic groups (25% Black, 25% Asian, 27% non-Hispanic White, 23% Hispanic) were randomized to a control group, receiving negligible carotenoids (177 mL apple juice/d), moderate-dose group, receiving 4 mg total carotenoids/d (177 mL orange-carrot juice/d), or high-dose group, receiving 8 mg total carotenoids/d (355 mL orange-carrot juice/d). Skin carotenoid score and plasma total carotenoid concentrations (α-carotene, ß-carotene, ß-cryptoxanthin, lycopene, lutein, zeaxanthin) were assessed at baseline, 3 wk, and 6 wk (n = 158 completed the trial). Repeated measures linear models were used to examine skin and plasma carotenoids over time and between groups. RESULTS: At 6 wk, participants in the high-dose and moderate-dose groups had significantly higher mean skin carotenoid scores [414.0 (SD = 100.6) and 369.7 (SD = 100.3), respectively] compared with those in the control group [305.2 (100.5)]. In the high-dose group, there was a 42% change in skin carotenoids from baseline (mean = 290.4) to a 6-wk follow-up (increase of 123, 123/290 = 42.4%). There was a 61% change in the plasma carotenoids in the high-dose group. CONCLUSIONS: The Veggie Meter is sensitive to increases in daily carotenoid intake in diverse racial/ethnic groups over 6 wk. CLINICAL TRIALS REGISTRY NUMBER: This trial was registered at clinicaltrials.gov as ID: NCT04056624. Study URL: https://clinicaltrials.gov/ct2/show/NCT04056624.

Pressure-Mediated Reflection Spectroscopy Criterion Validity as a Biomarker of Fruit and Vegetable Intake: A 2-Site Cross-Sectional Study of 4 Racial or Ethnic Groups.

BACKGROUND: Valid biomarkers of fruit and vegetable (FV) intake are needed for field-based nutrition research. OBJECTIVES: 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 y 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-photodiode array detection. Self-reported carotenoid and FV intake was assessed using a semiquantitative FFQ. Relations 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 BMI, 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 relations 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.