The Juice Study: Sensitivity of Skin Carotenoid Status to Detect Change in Intake

The US Dietary Guidelines for Americans recommends that individuals consume approximately 2-4 c of vegetables each day to reduce risk of chronic disease, but current methods for assessing intake are either inaccurate (self-report) or invasive (blood carotenoid levels). Recent research indicates that skin carotenoid status may be a useful biomarker of vegetable intake, but the sensitivity to dose in unknown. In this study, we propose to test the dose-response of skin carotenoids to consumption of 3 different levels of vegetable juice (with a control group receiving water). We will test skin carotenoids in two ways: using resonance Raman spectroscopy (RRS), which we have previously validated, and with a new technique, pressure mediated reflection spectroscopy (RS; the "Veggie Meter"). We will compare the two techniques during an 8-week provided tomato-based juice intervention. Skin carotenoid readings will be compared to blood carotenoid concentrations and single nucleotide polymorphisms (SNPs) of genes related to the uptake, transport, and metabolism of carotenoids will be examined in blood and saliva.

Inclusion criteria

• BMI 18.5-29.9 kg/m2

Exclusion criteria

• weigh less than 110 lbs
• currently dieting to lose weight
• allergic to tomatoes or vegetables
• pregnant, lactating, or planning to become pregnant
• currently use tobacco products or vape
• eat more that 2 cups of vegetables per day
• have high blood sugar (≥200 mg/dL)
• have high blood pressure (≥140/90 mm Hg)
• have a medical condition such as diabetes or high blood pressure
• taking medication that lowers cholesterol or triglycerides