In addition to self-reported dietary assessment, we also used the RS device to evaluate the use of skin carotenoids as a non-invasive, objective measure of dietary intake of fruits and vegetables. The RS device (Veggie Meter; Longevity Link Corp., Salt Lake City, UT, USA) was developed by those who originally developed resonance Raman spectroscopy as an objective indicator of carotenoid status(17 (link),21 (link),22 ). RS involves measurement of the skin carotenoid absorption via reflection under application of topical pressure(21 (link)). Applying a modest amount of topical pressure allows the carotenoid absorption spectra to be derived from the reflection spectra; the topical pressure provides an increase in the contrast between carotenoid absorption strength and the combined absorption background from other chromophores(21 (link)).
Trained research staff directed participants to place the right or left index finger (the side most comfortable for the participant) on a lens on the top of the RS device. A lever was then lowered over the finger which applied a gentle pressure, which temporarily blanches the skin by restricting blood flow, as is necessary to minimize interference of blood Hb with the RS carotenoid measurements. The device is linked to a tablet computer and shows the participant where his or her skin carotenoid reading falls on a histogram of all other readings prior to their measure. Each participant’s index finger was scanned three times and the average of the last two readings was used in this analysis. When time permitted, data collectors recorded the time three readings took using a stopwatch and recorded any qualitative comments made by participants specific to the RS device.
Trained research staff directed participants to place the right or left index finger (the side most comfortable for the participant) on a lens on the top of the RS device. A lever was then lowered over the finger which applied a gentle pressure, which temporarily blanches the skin by restricting blood flow, as is necessary to minimize interference of blood Hb with the RS carotenoid measurements. The device is linked to a tablet computer and shows the participant where his or her skin carotenoid reading falls on a histogram of all other readings prior to their measure. Each participant’s index finger was scanned three times and the average of the last two readings was used in this analysis. When time permitted, data collectors recorded the time three readings took using a stopwatch and recorded any qualitative comments made by participants specific to the RS device.
