NIR Light Tests for Blood Sugar

Researchers in Japan have demonstrated that the glycemic index (GI) can be determined by measuring the light emitted when the palm of the hand is illuminated with NIR light.

NIR spectroscopy measurements through the palm of the hand have proved the most suitable for the analysis of blood glucose for glycemic index determination.

A reliable, noninvasive technique for checking blood glucose has eluded medical analysts despite many years of research by teams in many countries. While NIR spectroscopy is ideally suited to the task, the wide variety of conditions under which the test would have to be run has prevented a clinically acceptable solution. However, by eliminating the variation due to person-to-person differences and sensing a larger area, real progress has been achieved. Lessons learned from optimization of the test may bring the "holy grail" of a clinical glucose sensor closer.

GI assessments, which measure blood glucose levels, are time-consuming, expensive and invasive for the human subjects. A series of blood samples is needed to check the increase in blood glucose after a person consumes a standard amount of carbohydrates.

Members of professor Kawano’s (second from left at back) team.

Professor Sumio Kawano and colleagues at the National Food Research Institute in Tsukuba, Japan, have now demonstrated that GI can be determined without the need for an excessive number of blood samples. They record the light emitted when the palm of the hand is illuminated. The results are not affected by skin pigmentation.

They have reported their findings in the latest issue of the Journal of Near Infrared Spectroscopy.

"Earlier studies with near-infrared methods were noninvasive but unreliable from patient to patient," Kawano said. "We have improved the reliability of blood glucose determinations with GI our primary focus. We simply shine a light on the palm of the hand and measure the near-infrared light which comes back."

The team, which includes PhD student Yasuhiro Uwadaira, used various parts of the body and small and large sensors in its work. The researchers are now applying the technology to assessing the GI values of a range of foods.

For more information, visit: www.nfri.affrc.go.jp