Examining potential modifiers of human skin and plasma carotenoid responses in a randomized trial of a carotenoid-containing juice intervention

Authors: JILCOTT PITTS, STEPHANIE - East Carolina University; WU, QIANG - East Carolina University; MORAN, NANCY - Children'S Nutrition Research Center (CNRC); LASKA, MELISSA - University Of Minnesota; HARNACK, LISA - University Of Minnesota

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2023
Publication Date: 9/23/2023
Citation: Jilcott Pitts, S.B., Wu, Q., Moran, N.E., Laska, M.N., Harnack, L. 2023. Examining potential modifiers of human skin and plasma carotenoid responses in a randomized trial of a carotenoid-containing juice intervention. Journal of Nutrition. 153(11):3287-3294. https://doi.org/10.1016/j.tjnut.2023.09.014.
DOI: https://doi.org/10.1016/j.tjnut.2023.09.014

Interpretive Summary: Carotenoids are colorful compounds found in fruits in vegetables which are absorbed and are distributed to human skin. Skin carotenoid concentrations can be measured non-invasively using an optical device to provide a biomarker for fruit and vegetable intake. However, in order to use this biomarker for monitoring changes in fruit and vegetable intake of the population, the robustness of the measure must be confirmed. The purpose of this study was to determine if any skin tone characteristics, demographic, or anthropometric characteristics impact the validity of skin carotenoid measures as a biomarker of changes in carotenoid intake. People of older ages had smaller increases in skin carotenoids than younger people, while people with greater hemoglobin saturation and lighter skin had greater increases in skin carotenoids in response to increased carotenoid intake. When taking all of the possible influences into account, the main determinants of an individual’s change in skin carotenoids in response to diet was their starting skin carotenoid concentration, with those with higher starting concentrations have smaller responses than those with lower starting concentrations. In conclusion, an individual’s starting skin carotenoid concentration may need to be taken into account when using the change in skin carotenoid concentration as a biomarker of dietary change.

Technical Abstract: Skin carotenoid measurements are emerging as a valid and reliable indicator of fruit and vegetable intake and carotenoid intake. However, little is known about the extent to which skin carotenoid responsivity to dietary changes differs based upon demographic and physiologic characteristics. OThis study examined potential effect modifiers of skin carotenoid and plasma carotenoid responses to a carotenoid-rich juice intervention. We leveraged data from two arms of a three-site randomized controlled trial of a carotenoid containing juice intervention (moderate dose = 6-ounces juice, 4mg total carotenoids/day, high dose = 12-ounces juice, 8 mg total carotenoids/day) (n = 106) to examine effect modification by age, self-categorized race/ethnicity, biological sex, baseline body fat, body mass index, skin melanin, skin hemoglobin, skin hemoglobin saturation, skin coloration, sun exposure, and baseline intake of carotenoids from foods. Skin carotenoid concentrations were assessed using pressure-mediated reflection spectroscopy (Veggie Meter®), and plasma carotenoid concentrations were measured using high-performance liquid chromatography. Results: In bivariate analyses, among the high dose group (8 mg/d), those of older age had lower skin carotenoid responsiveness than their younger counterparts, and those with greater hemoglobin saturation and lighter skin had higher skin carotenoid score responsiveness. In the moderate dose group (4 mg/d), participants from one site had greater plasma carotenoid responsiveness than those from other sites. In multivariate analyses, participants with higher baseline skin carotenoids had smaller skin carotenoid responses to both moderate and high doses. Changes in skin carotenoid scores in response to interventions to increase fruit and vegetable intake should be interpreted in the context of baseline skin carotenoid scores, but other variables (e.g., self-categorized race/ethnicity, biological sex, baseline body fat, body mass index, skin melanin, and sun exposure) did not significantly modify the effect of carotenoid intake on changes in skin carotenoid scores.