Oozing mouth ulcers are one of the many possible side-effects of radiation and chemotherapy treatments for cancer. The ulcers make it hard for patients to eat, worsening their suffering. Some must be fed by tube. A new way of treating these ulcers could brighten the future, however: light-emitting diodes (LEDs) tuned to the red end of the spectrum and placed into a patient’s mouth improve symptoms in more than 40% of cases.
REPRESENTATIVE IMAGE: Faster wound-healing is just one of the proposed uses of photobiomodulation (PBM), as therapies that use red and infrared light as the agent are known. (UNSPLASH)
Faster wound-healing is just one of the proposed uses of photobiomodulation (PBM), as therapies that use red and infrared light as the agent are known. Ophthalmologists and dermatologists have been using red light for some time to treat age-related decline in eyes and skin respectively. But PBM is also showing promise in the treatment of traumatic brain injuries; Alzheimer’s and Parkinson’s diseases; and even psychiatric disorders such as anxiety, depression, attention-deficit and hyperactivity, and post-traumatic stress.
Chain gang
The long wavelengths of red and infrared light give these parts of the spectrum tissue-penetrating power. That permits such light to reach and be absorbed by molecules of cytochrome c oxidase, a protein found in structures called mitochondria that are a cell’s power packs. The protein helps turn the energy from glucose into a molecule called ATP, which powers much of a cell’s biochemistry.
Red light activates cytochrome c oxidase molecules that have been switched off by nitric oxide, a so-called reactive oxygen species (ROS). The increased number of active cytochrome c oxidases boosts ATP production, providing more fuel for functions such as cellular repair. Simultaneously, the cell sees an increase in antioxidant enzymes that neutralise a wide range of other ROS molecules. That is important because ROS molecules can damage many other biomolecules. As bodies age and mitochondria wear out, more ROS molecules are produced accidentally. Among other things, this damps down ATP production in the old. As a result PBM allows you to “adjust the ageing mechanism”, claims Glen Jeffery, a neuroscientist at University College London’s Institute of Ophthalmology.
In 2020 he co-authored a pilot study, published in the Journals of Gerontology, which attempted a proof of concept applied to the retina. Professor Jeffery was interested in this part of the eye because, he explains, ATP declines by about 70% over the course of someone’s life. In the study, researchers found that volunteers over the age of 40 saw their colour-contrast vision improve by an average of 20%. Further work will be needed before such results can turn into treatments, however.
In another study to which Professor Jeffery contributed, and which was published in the Journal of Biophotonics in 2024, exposure to red light lowered blood-glucose spikes in people after they had consumed a sugary drink. Half of participants were exposed to 15 minutes of red light administered to their backs (so that they could not see what was going on). The others underwent a dummy treatment involving no light. In those exposed to red light, glucose peaks were 7.5% lower than in the control group. Though participants were not diabetic, these findings hint at applications which might help regulate blood-sugar levels in people who are.
There is also hope that red light can help people with brain and spinal-cord injuries suffered in accidents. At the University of Birmingham, David James Davies, a neurosurgeon, and his colleagues are developing a device made of LEDs embedded in silicone that they hope to implant into patients.
At the moment, Mr Davies says, he can do little for such people other than relieve pressure on injured areas by removing parts of their skulls or spines following an accident. He sees red-light therapy as a promising new option. The device his team is developing is some way from use in human patients, but will soon be tested in pigs.
The theory is that administering short doses of red light directly to the brain or spinal column could slow the wave of cell deaths that happens in the days after an accident. The light could stabilise the metabolisms of nerve cells and boost signals from their mitochondria that go on to help their genes promote growth and repair.
According to Mr Davies, experiments on cell cultures and rodents saw reductions in cell deaths of 20% or more. In practical terms, he says, that could mean the difference between needing a wheelchair and walking with a cane.
Other damage to the brain may also be susceptible to PMB. Parkinson’s and Alzheimer’s diseases are both linked to oxidative stress of the sort the treatment might relieve. Early-stage research suggests it could help those who do not respond to standard medications. Meanwhile, red light has been found to aid post-operative recovery, reducing pain and expediting healing. In physiotherapy, PBM decreases inflammation and boosts blood circulation, leading to less pain in tendon, muscle and joint injuries.
Well and good?
For Professor Jeffery, the idea that red light has useful biological functions should be no surprise. Humans evolved under the light of the sun. The modern world, however, has changed the kinds of light to which the human body gets exposed—windows, for instance, tend to block infrared, while office buildings are illuminated by LEDs that produce a surfeit of blue. That is bound to have effects on health, Prof Jeffery reckons. How far those effects stretch, however, is unknown. And that gap between knowledge and possibility has led, as night follows day, to the emergence of a “wellness” industry that pedals everything from red-light masks and blankets, to infrared saunas and yoga studios, as skin-rejuvenators, muscle-soothers and sleep-enhancers.
Some of these may work. The trouble, says Professor Jeffery, is twofold. First, commercial interests have coloured many research outcomes with questionable practices, including small sample sizes and insufficient use of control groups. Second, few of these applications pay attention to dose. The distance from light source to affected tissue, the specific wavelengths involved, the voltage at which the equipment operates and the length of exposure can all influence the outcome.
In particular, more exposure to red light does not necessarily mean a better result. Overexposure can create what Professor Jeffery calls a “traffic jam” in a cell’s metabolism, with a consequent fall in ATP production. For healthy people, his advice is to buy a dog. That way you will go outside for at least 20 minutes several times a day and get all the red light you need.
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