Factors affecting the biomarker
While skin carotenoid status is clearly a biomarker of diet, smoking leads to substantial reductions in plasma carotenoid levels. Partially this is caused by lower intakes of carotenoids. Since skin carotenoid levels correlate with blood levels, skin levels in smokers are reduced as well. Sun exposure appears to affect skin carotenoid status, too, but the overall impact on carotenoids is fairly modest under normal circumstances. Genetic variation is a significant determinant of individual carotenoid concentrations in blood, but the impact on total carotenoids in blood would be expected to be less, and there are no published studies reporting genetic variation in relation to skin carotenoid status, cross-sectionally or in response to intervention. When analyzed by a chemical assay based on urinary malondialdehyde excretion, an indicator of oxidative lipid damage, people with high oxidative stress had significantly lower skin carotenoid levels than people with low oxidative stress. These observations suggest that skin carotenoid scores might be useful as a surrogate marker for general antioxidant status. Age does not appear to be an important determinant of skin carotenoid status in adults, although a wide age range has not been systematically evaluated. In babies and young children, however, those who are older on average have higher skin carotenoid status. In terms of gender, on average, women have higher skin carotenoid status than men, consistent with what is known about adipose tissue and plasma carotenoids, likely reflecting greater intake of fruits and vegetables in women along with smaller body size.
High fruit and vegetable (F/V) intake has been associated with lowered risk of various cancers, cardiovascular disease, age-related degenerative eye diseases, and obesity. Many countries, including the U.S., are supporting interventions to increase F/V intake among their citizens. National policy, such as Healthy People 2020 and the Dietary Guidelines for Americans call for increases in F/V intake in children and adults.
An important feature of any biomarker is the variability between subjects. Ideal biomarkers would vary widely across different individuals within a population, but be relatively constant over time within an individual. VEGGIE METER® fulfills both requirements very well, as demonstrated in the two figures shown below.
43 subjects
Carotenoid fortified acai juice (9 mg/day)
Response to dietary intervention
There is considerable interest in using the VEGGIE METER® to evaluate whether or not interventions designed to improve fruit and vegetable intake actually change intake behaviors and improve nutritional status. This is a critical research need, because without objective verification that behavior change has occurred, results of trials (of health outcomes, as well as of intake) are difficult to interpret. The ideal method for assessing response to intervention is in the setting of controlled intervention studies. In partnership with the U.S. Department of Agriculture, our group assessed skin carotenoid status in response to several different dietary interventions, including a carotenoid depletion phase (provision of minimal carotenoid-rich foods for six weeks), followed by a high fruit and vegetable-provided diet (eight weeks), followed by another depletion diet (six weeks), and then subjects returned to their self-selected diets for an additional eight weeks. Skin carotenoid levels decreased during depletion and increased during high-carotenoid feeding, with skin carotenoid status tracking similarly to plasma carotenoids although the rates of decrease (during depletion) were faster in plasma versus skin. Skin carotenoids had not yet plateaued by 8 weeks post-intervention, suggesting that they reflect intake over at least the prior 2+ months. Thus, multiple lines of evidence now show that skin carotenoid status is responsive to carotenoid intervention involving supplements, and carotenoid-rich fruits and vegetables consumed in typical US diets.
3 subjects
Carrot juice (2 x 3oz/day)
Carotenoids have a characteristic absorption band in the blue wavelength region of the visible light spectrum. The absorption strength scales directly with the concentration of carotenoids present in the skin. Using our patented and validated reflection spectroscopy approach, skin carotenoid levels can be objectively measured in a non-invasive rapid fashion. Importantly, the VEGGIE METER® corrects for pigmentation from melanin and blood and therefore is accurate across all ethnicities.
Since higher VEGGIE METER® scores reflect greater F/V intake, lack of smoking, and lack of adiposity, it is attractive for use as an integrated biomarker of overall health in longitudinal studies testing future chronic disease risks. In intervention settings, skin carotenoid status responds predictably and consistently to carotenoid interventions, and as objective biomarker of change should be very attractive for inclusion in F/V-based intervention trials.
For a given subject, the score is highly repeatable, varying only slightly between measurements. The magnitude of the Standard Deviation, here 3.9%, can be decreased or increased somewhat depending on skin smoothness.
Rapid screening of large populations
The veggie meter provides an attractive objective indicator for F/V intake. It can identify populations at particular risk for inadequate intake of F/V, evaluate the success of interventions aimed at increasing F/V intake, and serve as a biomarker associated with better health.
Noninvasive assessment of skin carotenoids
Significant skin carotenoid increases are observable after several weeks in response to supplementation of normal diet with carotenoid - containing juices. I. V. Ermakov, W. Gellermann, “Dermal Carotenoid Measurements via Pressure Mediated Reflection Spectroscopy”, J. Biophotonics 5, 559-570 (2012)
OPTICS FOR HEALTH
Wide inter-subject variation of skin carotenoid levels (0-850) with bell-shaped distribution indicates widely varying nutritional status between subjects
•illumination of skin with white light LED; detection of diffusely reflected light
•10 sec. measurement of finger tip
•skin contact lens provides temporary blood clearing of measured tissue
•interfaced to laptop computer
•instantaneous determination of skin carotenoid score
•score scales linearly with tissue concentration
•automatic correction for residual oxy-hemoglobin, de-oxy hemoglobin, melanin, and tissue scattering
The VEGGIE METER® -- skin carotenoids as indicator of fruit and vegetable intake and biomarker associated with better health
VEGGIE METER® Features
Significant skin carotenoid decreases observable in depletion phase of controlled feeding intervention study. L. Jahns, L. K. Johnson, S. T. Mayne, B. Cartmel, M. J. Picklo, I. V. Ermakov, W. Gellermann, L. D. Whigham, “Skin and Plasma Carotenoid Response to a Provided Intervention Diet High in Vegetables and Fruit: Uptake and Depletion Kinetics”, American Journal of Clinical Nutrition (2014)
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