New technology measures biomarker by bouncing laser light off skin

What did you have for lunch yesterday? How many times a month do you eat nuts? How about your kids - how many servings of vegetables did they consume today?

It's no secret that it is hard to recall the details of our meals, and that frustrating fact lies at the heart of nutrition research, complicating the task of linking foods to health outcomes like diabetes and heart disease.

Some researchers look instead for telltale substances, or biomarkers, in the body that give information about how much of a certain type of food a person has eaten recently. But that solution isn't ideal, as measuring biomarkers often requires blood, urine or even skin samples. The process can be costly, painful and cumbersome.

But, for researchers who study fruits and vegetables in the diet, there may soon be an easier way. Scientists at the Yale School of Public Health are testing a new technology that measures a biomarker by simply bouncing blue laser light off the skin. It is painless and fast and gives results in about a minute.

Susan T Mayne, head of the division of Chronic Disease Epidemiology, and her longtime collaborator, Brenda Cartmel, a research scientist in the same division, have worked with a group of physicists at the University of Utah to create and test two prototype devices that measure skin carotenoids, which are biomarkers for fruit and vegetable intake that are usually measured in the blood.

''It really derived from an observation that people have known about for decades,'' says Mayne, ''and that is when people have high-vegetable diets they develop a yellow skin coloration that is particularly noticeable in the palm of the hand because of the accumulation of carotenoids in the skin. And we thought, 'Can we use that as a new approach to measure carotenoids in the body noninvasively?'''
The device is a modern twist on a decades-old technology known as Resonance Raman Spectroscopy (RRS), which measures changes in energy levels of electrons in molecules after they have been excited by laser light. It consists of a flexible fiberoptic probe connected to a boxlike central machine; the probe is held against a study volunteer's palm for about 30 seconds while the light interacts with carotenoids in the skin.