Red light is an incredible tool that can have meaningful and lasting biological impacts. It can reduce pain, heal wounds, improve our skin, make us stronger, and much more. The fact that something as simple as light can have these numerous and profound effects is pretty astounding. But red light becomes even more amazing when you consider how it works. Since the early 70’s, researchers have uncovered a wealth of information about the benefits of red light and the biology behind it. The ways that red light is able to influence the fantastically complex machinery of a single cell is just too cool not to share. So let’s dig in.
There are a number of ways that red light works to enhance cellular function (De Freitas & Hamblin, 2016). One of the more recently discovered mechanisms involves a gaseous molecule called nitric oxide, which serves several important functions in our bodies. For example, it’s essential for vasodilation or the relaxing of the smooth muscle in your blood vessels. When blood vessels are relaxed, blood flows more easily, which both reduces blood pressure and increases blood flow. While nitric oxide is an important part of a healthy body, it isn’t always a team player.
Nitric oxide molecules and oxygen molecules are structurally very similar, which means that nitric oxide can steal oxygen’s spot at important receptor sites. During cellular respiration (the process our cells use to turn oxygen into energy in the form of ATP) oxygen has to compete with nitric oxide for its spot on a special part of our mitochondria known as cytochrome c oxidase (CCO). Importantly, this is where the last stage of cellular respiration- production of ATP- takes place (check out this post to learn more about CCO). The two molecules basically have to race each other to the binding site on CCO. When oxygen wins the race, the cellular respiration process is completed, oxygen is used to create ATP, and everyone is happy. When nitric oxide gets there first, the cellular respiration process grinds to a halt and no ATP is created. If the blockage created by nitric oxide is short-lived, it doesn’t necessarily cause damage to the cell. But when the blockage persists, it can result in a total breakdown of the cell (Poderoso et al., 2019). This is where red light steps in to save the day.
Current evidence suggests that when the light energy of red light is absorbed by CCO, nitric oxide is ejected from its position, making room for oxygen and freeing up CCO to do its thing (De Freitas & Hamblin, 2016). The removal of nitric oxide from CCO has been shown to improve cellular respiration and increase the production of ATP (De Freitas & Hamblin, 2016). This is critical because cells need ATP to survive. In addition to improving cellular respiration and energy production, removing nitric oxide from CCO is also thought to increase its bioavailability (Mitchell & Mack, 2013). In other words, when nitric oxide isn’t busy clogging up cellular respiration, it’s free to get back to work serving one of its many beneficial purposes, like improving blood flow.
The biological mechanisms behind how red light works are so complex that even after decades of research we’re still learning new things. The recent discovery of the role nitric oxide plays could help explain some of the amazing therapeutic benefits of red light therapy. Nitric oxide is an important part of a healthy body, but it can also cause damage by clogging up cellular respiration and preventing the cell from creating ATP. Red light has the power to unclog cellular respiration by giving nitric oxide the boot. When nitric oxide is ejected, cellular respiration and energy production can resume and nitric oxide can get back to being a team player.
De Freitas, L. F., & Hamblin, M. R. (2016). Proposed Mechanisms of Photobiomodulation or Low-Level Light Therapy. IEEE Journal of Selected Topics in Quantum Electronics, 22(3), 348–364. https://doi.org/10.1109/JSTQE.2016.2561201
Eshagi, E., Sadigh-Eteghad, S., Mohaddes, G., & Rasta, S. H. (2019). Transcranial Photobiomodulation Prevents Anxiety and Depression via Changing Serotonin and Nitric Oxide Levels in Brain of Depression Model Mice: A Study of Three Different Doses of 810 nm Laser. Lasers in Surgery and Medicine, 51(7). https://pubmed.ncbi.nlm.nih.gov/30883832/
Mitchell, U. H., & MacK, G. L. (2013). Low-level laser treatment with near-infrared light increases venous nitric oxide levels acutely: A single-blind, randomized clinical trial of efficacy. American Journal of Physical Medicine and Rehabilitation, 92(2), 151–156. https://doi.org/10.1097/PHM.0b013e318269d70a
Poderoso, J. J., Helfenberger, K., & Poderoso, C. (2019). The effect of nitric oxide on mitochondrial respiration. Nitric Oxide – Biology and Chemistry, 88(October 2018), 61–72. https://doi.org/10.1016/j.niox.2019.04.005