Resonance Raman spectroscopic evaluation of skin carotenoids as a biomarker of carotenoid status for human studies

Abstract

Resonance Raman spectroscopy (RRS) is a non-invasive method that has been developed to assess carotenoid status in human tissues including human skin in vivo. Skin carotenoid status has been suggested as a promising biomarker for human studies. This manuscript describes research done relevant to the development of this biomarker, including its reproducibility, validity, feasibility for use in field settings, and factors that affect the biomarker such as diet, smoking, and adiposity. Recent studies have evaluated the response of the biomarker to controlled carotenoid interventions, both supplement-based and dietary [e.g., provision of a high-carotenoid fruit and vegetable (F/V)-enriched diet], demonstrating consistent response to intervention. The totality of evidence supports the use of skin carotenoid status as an objective biomarker of F/V intake, although in the cross-sectional setting, diet explains only some of the variation in this biomarker. However, this limitation is also a strength in that skin carotenoids may effectively serve as an integrated biomarker of health, with higher status reflecting greater F/V intake, lack of smoking, and lack of adiposity. Thus, this biomarker holds promise as both a health biomarker and an objective indicator of F/V intake, supporting its further development and utilization for medical and public health purposes.

Keywords: Beta-carotene; Biomarker; Carotenoids; Resonance Raman spectroscopy; Skin.

Figure 1

RRS spectrum of a solution of beta-carotene in acetone (a); typical raw skin spectrum (b) featuring weak carotenoid RRS peaks superimposed on a strong fluorescence background; processed carotenoid RRS spectrum (c) obtained after subtraction of fluorescence background. Skin carotenoid C-C and C=C RRS peaks are detectable with high signal-to- noise ratios. Taken with permission from Ermakov et al.

Figure 2

A. Histogram showing distribution of skin total carotenoids in the palm, n = 74 healthy adults. Taken with permission from Mayne et al. B. Histogram showing distribution of skin total carotenoids in the palm, n = 381 preschool children. Taken with permission from Scarmo et al. Note that the scales in Figures 2A and 2B are not comparable as one was normalized to an external standard calibrator.

Figure 3

Clinical use of portable RRS scanner with fiber optical module for heel skin carotenoid measurements in infants. Taken with permission from Ermakov et al.