February 21, 2024

expert reaction to study suggesting that red light can reduce blood glucose levels

A study published in the Journal of Biophotonics looks at red light reducing blood glucose levels.

Prof Russell Foster, Professor of Circadian Neuroscience, University of Oxford, said:

“The findings presented in this study are interesting. However, looking at the paper the authors have not described the emission source for the red light in any detail and as such there could potentially be a heat effect at play, meaning that the heat produced by infrared light could be driving the change in blood glucose levels seen in the participants in the study. I think the study would have been strengthened if the authors had managed to control for the potential effect of the heat by using an infrared cut-off filter that would have transmitted the red light but blocked the heat.

“The authors suggest a potential mechanism for the reduction in blood glucose levels as the absorption of the red light by a specific molecule, cytochrome C oxidase, in the mitochondria of cells which then increases the energy of the cell enabling faster glucose metabolism and reduction in overall blood glucose levels. However, the data presented in this study cannot alone prove the causality of this mechanism. The best way to do this would be to undertake an “action spectrum” – exposing the skin to different wavelengths of light and assessing the response. If cytochrome C oxidase is mediating the effects described, then the action spectrum should mirror the distinctive absorption spectrum of this molecule. It’s not an easy experiment, but this would be a great next step.”

Prof Keith Frayn, Emeritus Professor of Human Metabolism, Emeritus Fellow at Green Templeton College, University of Oxford, said:

“The authors have shown that exposure of the skin and muscles of the back to red light for 15 minutes before taking a glucose drink can lower the blood glucose response to that drink.  This builds upon earlier work by the same authors showing the same effect in bumblebees.  If confirmed later in people with diabetes, this could be the foundation of a useful intervention.  But these intriguing findings should be regarded as quite preliminary.  More investigations would be needed before we can fully assess this effect.  Importantly, we need to know whether this is a true metabolic effect, or whether, for instance, the warming effect of the red light exposure alters patterns of blood flow, potentially altering the nature of the blood sampled by pricking a finger.  We also need more information on what happens to the glucose that doesn’t appear in the blood.  If, as the authors suggest, this is being used in cells that have been stimulated by the red light, then this is effectively increasing the rate of metabolism rather like in brown fat, and should be detectable as local heat generation.  Any non-pharmacological intervention that ‘improves metabolism’ is to be welcomed, but further research is needed before these findings can be put into practice.”

‘Light stimulation of mitochondria reduces blood glucose levels’ by Michael B Powner et al. was published in Journal of Biophotonics at 00:01 UK time Wednesday 21 February 2024.

Declared interests

Prof Keith Frayn: I have no conflict of interest to declare other than as an author of books on human metabolism.