Criterion-related Validity of Spectroscopy-based Skin Carotenoid Measurements as a Proxy for Fruit and Vegetable Intake in Diverse Populations: A Systematic Review

Authors: RADTKE, MARCELA - University Of California, Davis; JILCOTT PITTS, STEPHANIE - East Carolina University; Jahns, Lisa; FIRNHABER, GINA - East Carolina University; ROBINSON, BRITT - University Of California, Davis; ZENG, APRIL - East Carolina University; SCHERR, RACHEL - University Of California, Davis

Submitted to: Advances in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2020
Publication Date: N/A
Citation: 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 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. The goal of this systematic review was to evaluate the validity and reliability of the use of skin scans to assess carotenoid-rich vegetable and fruit intake. We examined current research using three different methods of skin carotenoid detection; resonance Raman spectroscopy, reflection spectroscopy, and spectrophotometry. Each of the methods were moderately to strongly associated with either blood carotenoids or dietary intake, suggesting that skin scans are a valid method of non-invasively measuring vegetable and fruit intake. However, more research is needed in people of varying race/ethnicities and ages.

Technical Abstract: Carotenoids are a category of health-promoting phytonutrients that are commonly found in a variety of fruits and vegetables. As they are almost exclusively found in fruits and vegetables, carotenoids have been used to approximate dietary fruit and vegetable intake. Carotenoids are consumed, metabolized, and then deposited in the blood, skin and other body tissues. Emerging evidence suggests spectroscopy-based skin carotenoid measurement as a valid, objective, non-invasive method to approximate fruit and vegetable intake. Spectroscopy-based skin carotenoid measurement overcomes bias and error inherent in self-reported dietary recall methods, and issues related to obtaining, storing and processing invasive blood samples. The objective of this systematic review was to examine criterion-related validity of spectroscopy-based skin carotenoid measurement as a proxy for fruit and vegetable intake. The three methods examined include resonance Raman spectroscopy (RRS), pressure-mediated reflection spectroscopy (RS), and spectrophotometers. A comprehensive literature search of PubMed, EMBASE, Cumulative Index of Nursing and Allied Health Literature (CINAHL), ProQuest Search, Cochrane Database of Systematic Reviews (CDSR), and Cochrane Central Register of Controlled Trials (CENTRAL) was performed in December 2018, yielding 7,931 citations. Studies that examined associations between spectroscopy-based measures of skin carotenoids and plasma/serum carotenoids and/or dietary intake were identified. The articles were reviewed independently by at least two reviewers to determine eligibility for inclusion, resulting in 23 included articles. Of the included articles, all 23 studies resulted in positive and significant correlations or associations between spectroscopy-based skin carotenoid measures and plasma or serum carotenoids, dietary fruit and vegetable intake, or both. Fifteen studies were conducted using RRS, two studies were conducted using RS, and six studies were conducted using spectrophotometers. A majority of the studies involved adult participants, however, two studies looked at infants and six studies evaluated carotenoid status in children. Seventeen of the 23 studies specified the racial/ethnic groups from which the samples were drawn, with six including at least 20% of the sample from a minority, non-white group. The findings of this systematic review support the use of spectroscopy as a non-invasive, objective method for estimating fruit and vegetable intake in diverse human populations, though more validation research is needed particularly using RS and spectrophotometers among racially/ethnically diverse populations and in populations of varying ages.