Concurrent validity of skin carotenoid status as a concentration biomarker of vegetable and fruit intake compared to multiple 24-hour recalls and plasma carotenoid concentrations across one year: a cohort study

Authors: Jahns, Lisa; JOHNSON, LUANN - University Of North Dakota; Conrad, Zachary; Bukowski, Michael; RAATZ, SUSAN - Former ARS Employee; PITTS, STEPHANIE - East Carolina University; WANG, YOUFA - Ball State University; ERMAKOV, IGOR - Longevity Link Corporation; GELLERMANN, WERNER - Longevity Link Corporation

Submitted to: Nutrition Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2019
Publication Date: 11/21/2019
Citation: Jahns, L.A., Johnson, L., Conrad, Z.S., Bukowski, M.R., Raatz, S., Pitts, S., Wang, Y., Ermakov, I., Gellermann, W. 2019. Concurrent validity of skin carotenoid status as a concentration biomarker of vegetable and fruit intake compared to multiple 24-hour recalls and plasma carotenoid concentrations across one year: a cohort study. Nutrition Journal. 18:78. https://doi.org/10.1186/s12937-019-0500-0.
DOI: https://doi.org/10.1186/s12937-019-0500-0

Interpretive Summary: Vegetable and fruit intake is associated with maintenance of a healthy body weight and reduced risk of chronic diseases such as heart disease and cancer. However, Americans do not eat enough to meet the recommendations of the Dietary Guidelines for Americans. Measuring if public health intervention studies of ways to increase people’s consumption of vegetables and fruits is difficult as people are usually asked if their diet changed or not, which is prone to mistakes. Another way to assess if the intervention is working is to measure substances called carotenoids in the blood. Carotenoids are the brightly colored pigments found in vegetables and fruits, such as the orange color in carrots. But blood draws are invasive and expensive. Carotenoids also accumulate in the skin and can be measured performing a quick and painless hand scan. In this study, we compared two different methods of measuring skin carotenoids, and compared it to blood carotenoids and self-reported vegetable and fruit intake. We found that both skin methods were strongly related to blood carotenoids, indicating that the less-invasive skin carotenoid status can be used to approximate blood carotenoid concentrations, at least to rank people from high to low. We also found that the self-reported vegetable and fruit intake was only weakly related to blood carotenoid or skin carotenoid status. This indicates that skin carotenoid status works as well as blood for measuring vegetable and fruit intake, but is non-invasive, faster, less expensive than blood, and perhaps more reliable than self-reported intake.

Technical Abstract: Background: Biological markers of vegetable and fruit (VF) intake are needed both for nutrition surveillance and for the evaluation of nutrition interventions. Optically assessed skin carotenoid status (SCS) has been proposed as a marker of intake but there are few published validity studies to date. Objective: The objective of the study was to examine the concurrent validity of multiple methods of assessing VF intake cross-sectionally and seasonally over one year and to discuss the relative merits and limitations of each method. Design: Fifty-two women completed a 1-year longitudinal study that included 1) SCS assessment using resonance Raman spectroscopy (RRS) and using pressure-mediated reflection spectroscopy (RS) at 12 timepoints, 2) thirty-six 24- hour recalls using the Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24), and 3) plasma carotenoid concentrations measured every 3 months. Pearson correlation coefficients and mixed linear models were used to estimate pairwise correlations between RRS, RS, ASA24, and plasma carotenoids. Results: RS and RRS were strongly correlated at baseline and over the year (r = 0.86 and 0.78; respectively, P < 0.001). RS was strongly correlated with plasma carotenoids at baseline (r = 0.70) and moderately across the year (r = 0.65), as was RRS (r = 0.77 and 0.69, respectively, all P < 0.001). At baseline, self-reported VF was weakly correlated with RRS (r = 0.33; P = 0.016), but not with RS or plasma carotenoids. Across the year, self-reported VF intake was weakly correlated with both RS (r = 0.37; P = 0.008), RRS (r = 0.37; P = 0.007), and with plasma carotenoids (r = 0.36; P < 0.008). Conclusions: SCS is strongly to moderately correlated with plasma carotenoid concentrations both cross-sectionally and longitudinally, indicating that it can be a powerful tool to assess carotenoid-rich VF intake in populations.