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Non-invasive assessment of Glycaemic Index using near infrared light

A reliable, non-invasive technique for checking blood glucose has eluded medical analysts despite many years of research by teams in many countries. Whilst near infrared (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. Furthermore, lessons learnt from optimisation of the test may bring the “holy grail” of a clinical glucose sensor nearer.

The glycaemic index (GI) of foods is a valuable indicator of the influence of a food on blood glucose levels. GI assessments are time consuming, expensive and invasive of the human subjects. A series of blood samples are needed to check the increase in blood glucose after consuming a standard amount of a carbohydrate.

Professor Sumio Kawano and colleagues at the National Food Research Institute, 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 (JNIRS). “Earlier studies with near infrared methods were non-invasive but unreliable from patient to patient.” Professor 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 Mr Yasuhiro Uwadaira, used various parts of the body and small and large sensors in their work. They are now applying the technology to assess the GI values of a range of foods.

*Y. Uwadaira, N. Adachi, A. Ikehata and S. Kawano, J. Near Infrared Spectrosc. 18(5), 291–300 (2010), doi: 10.1255/jnirs.895,