|Johnson, Luann -|
|Mayne, Susan -|
|Cartmel, Brenda -|
|Ermakov, Igor -|
|Gellermann, Werner -|
|Whigham Grendell, Leah|
Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2014
Publication Date: N/A
Interpretive Summary: Vegetable and fruit intake is associated with maintenance of a healthy body weight and reduced risk of chronic diseases such as CVD and diabetes. However, Americans do not eat enough to meet the recommendations of the Dietary Guidelines for Americans. Assessing the effectiveness of 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 can be full of errors. Another way to assess if the intervention is working is to measure carotenoids in the blood, as carotenoid compounds are found primarily in vegetables and fruits, but blood draws are invasive and expensive. Carotenoids also accumulate in the skin and can be measured using Resonance Raman spectroscopy (RRS) by performing a quick and painless hand scan. In this study, we compared skin to blood carotenoid measurements during a controlled feeding intervention where people ate different amounts of vegetables and fruits. Twenty-nine people ate a low-carotenoid diet for 6 weeks, a high-carotenoid diet (6 c/day vegetables and fruit) for 8 weeks, a low-carotenoid diet again for 6 weeks, and then their usual diet for the final 8 weeks. People had multiple blood draws and skin scans during the study. We found that skin and blood carotenoid levels were highly correlated during the entire study. This indicates that skin carotenoid status assessed by RRS works as well as blood for measuring vegetable and fruit intake, but is non-invasive, faster, less expensive than blood, and more reliable than self-reported intake.
Technical Abstract: Background: Objective biomarkers are needed to assess adherence to vegetable and fruit intervention trials. Blood carotenoids are considered the best biomarker of vegetable and fruit intake but collecting blood is invasive and the analyses are relatively expensive for population studies. Resonance Raman spectroscopy (RRS) is an innovative method to assess carotenoids in skin non-invasively. Objective: Our objective was to compare blood carotenoid concentrations to skin carotenoid assessments by RRS during a controlled feeding intervention. Design: Twenty-nine participants consumed low-carotenoid diets (6 wks, phases 1 & 3), a provided diet containing 6 c/day vegetables and fruit (8 wks, phase 2) and usual diet (final 8 wks, phase 4). Results: At baseline, skin and plasma total carotenoid values were correlated (r = 0.61, P < 0.001). Skin and plasma carotenoid values decreased (P <0.001) 36 and 30%, respectively, from baseline to end of phase 1, then increased (P <0.001) over 200% at end of phase 2. Plasma carotenoids returned to baseline concentrations by the middle of phase 3 and skin carotenoid levels by the middle of phase 4. Skin carotenoid status predicted plasma values using a mixed linear model including all time points (r = 0.72, P < 0.001), indicating that changes in skin carotenoid status closely follow changes in plasma across a broad range of intakes. At the individual level, skin carotenoids predicted plasma values (r = 0.70, P < 0.001) over all time points. Conclusions: Skin carotenoid status assessed by resonance Raman spectroscopy is a non-invasive, objective biomarker of changes in vegetable and fruit intake.