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Laser probe knows if you ate your veggies

A diet full of fruits and vegetables is good for your health, but accurately measuring how much people—especially children—actually eat can be challenging.

Researchers have demonstrated for the first time that a new device, which uses blue laser light to quickly and painlessly scan the skin of a subject’s palm, accurately measures changes in a biomarker known as skin carotenoids in response to an intervention involving a diet enriched in fruits and vegetables.

non-invasive device measures vegetables in diet
The probe is held against a person’s palm for about 30 seconds while the light interacts with carotenoids in the skin. (Credit: Yale)

In the American Journal of Clinical Nutrition, researchers report that the noninvasive technique tracked skin carotenoid changes over a 28-week period. That time was divided into distinct dietary phases marked by high and low intake of provided fruit and vegetables, along with a phase in which study participants resumed their usual diets.

The palm-reading device, which uses resonance Raman spectroscopy (RRS), has the potential to help nutritionists and other medical professionals measure and improve the diets of children and adults alike.

“There is great interest in the development of objective biomarkers of dietary intake, especially biomarkers that can be measured noninvasively,” says coauthor Susan T. Mayne, professor of epidemiology at Yale University and a developer of the device.

“Our earlier studies demonstrated a correlation between skin carotenoids and fruit and vegetable intake—this new paper demonstrates that the biomarker was sensitive to changes in fruit and vegetable intake in the intervention setting.

“Many diet interventions lack objective verification that subjects actually changed intake—this research demonstrates that skin carotenoids can serve that purpose.”

Results in 1 minute

The RRS device works by measuring changes in energy levels of electrons in molecules after the laser has excited them. It consists of a flexible fiberoptic probe connected to a boxlike central machine.

The probe is held against an individual’s palm for about 30 seconds while the light interacts with carotenoids in the skin. Then software on an attached laptop processes the results, which takes another 30 seconds.

Diets rich in fruit and vegetables have been linked to important health outcomes, including reductions in cardiovascular disease, type 2 diabetes, and some forms of cancer. But only 11 percent of the US population currently meets the daily recommendations for vegetable consumption, while 20 percent meet the guideline for fruit.

Subjective methods of measuring fruit and vegetable intake, such as questionnaires, are prone to bias and error. Measuring carotenoids in the blood, meanwhile, provides a highly accurate result, but the invasive process is more expensive and especially difficult with children.

Brenda Cartmel, a senior research scientist and lecturer at the Yale School of Public Health, is a co-author of the paper, along with researchers from the USDA/Agricultural Research Service Grand Forks Human Nutrition Research Center, and the University of Utah.

Source: Yale University