A reflection-spectroscopy measured skin carotenoid score strongly correlates with plasma concentrations of all major dietary carotenoid species except for lycopene

Authors: WU, QIANG - East Carolina University; WEBB CHERRY, CHERYL - East Carolina University; JILCOTT PITTS, STEPHANIE - East Carolina University; LASKA, MELISSA - University Of Minnesota; CRAFT, NEAL - Craft Nutrition Consulting; MORAN, NANCY - Children'S Nutrition Research Center (CNRC)

Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2024
Publication Date: 11/29/2024
Citation: Wu, Q., Webb Cherry, C., Jilcott Pitts, S., Laska, M.N., Craft, N., Moran, N.E. 2024. A reflection-spectroscopy measured skin carotenoid score strongly correlates with plasma concentrations of all major dietary carotenoid species except for lycopene. Nutrition Research. 133:127-137. https://doi.org/10.1016/j.nutres.2024.11.010.
DOI: https://doi.org/10.1016/j.nutres.2024.11.010

Interpretive Summary: Eating adequate fruits and vegetables is an important part of a healthy diet for children and adults. Many people do not eat enough fruits and vegetables, but it can be difficult for healthcare providers, community health workers, and support organizations to quickly and objectively assess an individual’s and a group’s fruit and vegetable intake. Skin carotenoids are a biomarker that can be measured noninvasively using a light based measurement. Carotenoids are colorful compounds found in fruits and vegetables and are deposited in skin. Different foods have different carotenoid species present, for instance as tomatoes having red lycopene, dark green leafy vegetables having lutein and zeaxanthin, and deep orange vegetables having beta-carotene. Currently, skin carotenoid measurements are quantified as an aggregate score for several specific carotenoids found in the skin, however it is unknown which specific carotenoids contribute to and drive skin carotenoid score. This study analyzed two groups of adults’ carotenoid intakes, plasma carotenoid concentrations, and skin carotenoid scores and found that skin carotenoid scores were moderately to strongly correlated with all major dietary carotenoids except lycopene. This result suggests that tomato intake may not be strongly detected by skin carotenoid score measurements. Future research into device settings and implications of this finding for diet assessment is needed.

Technical Abstract: Skin carotenoids can be measured non-invasively using spectroscopy methods to provide a biomarker of total dietary carotenoid and carotenoid-rich fruit and vegetable intake. How- ever, the degree to which skin carotenoid biomarkers reflect intakes of specific carotenoids must be determined for specific devices. Previously, findings were mixed regarding the correlation between reflection spectroscopy (RS)-assessed skin carotenoids and individual plasma carotenoid concentrations. The current study expands on prior analyses to exam- ine the cross-sectional associations between adult RS-assessed skin carotenoids and indi- vidual carotenoid species intakes and plasma concentrations, controlling for potential co- variates. We hypothesized that RS-assessed skin carotenoid scores would strongly correlate with all major plasma carotenoid species other than lycopene. Cross-sectional data from 2 prior studies (n = 213 and n = 162) examining the validity and sensitivity of RS-assessed skin carotenoids as a biomarker of fruit and vegetable intake were used. Skin carotenoids were assessed using the Veggie Meter, which quantifies combined skin carotenoid con- centrations. Plasma concentrations of a-carotene, ß-carotene, ß-cryptoxanthin, lycopene, and lutein and zeaxanthin were determined using high-performance liquid chromatogra- phy. Self-reported carotenoid intake was estimated from validated food frequency ques- tionnaires. Skin carotenoid scores correlated moderately to strongly with individual plasma carotenoid species (Pearson’s r = 0.52 to r = 0.78) except for lycopene ( r = 0.04 to r = 0.07). Low correlations between skin carotenoid score and lycopene plasma concentrations and intake could be due to differential deposition, preferential oxidation/degradation, and/or device measurement bias. Validating skin carotenoid measurement techniques relative to other concentration biomarkers informs the interpretation of skin carotenoid biomarkers.