Illustration: Matija Medved | Animation: Alexis Jamet

Elemental Light Week

The Magic and the Myths Behind Infrared Light

Can infrared light treat everything from arthritis to Alzheimer’s disease?

This story is a part of Elemental Light Week, a 5-day series on what light does for your body, brain, and well-being.

HHumans are inundated with light waves every second of every day. There’s the light we think about — visible light pouring forth from the sun and electric light bulbs and ultraviolet (UV) light that turns our skin red, tan, and eventually wrinkled. And there’s the light we don’t think about, like the radio waves bouncing off of us and the gamma rays that shoot right through us. Given the ubiquity, diversity, and power of light, everyone from neurologists to dermatologists to wellness gurus are trying to harness light waves to enhance and heal the body. And although it sounds pretty fringe, it turns out there’s more to light than meets the eye.

In part because of the clear impact UV light has on the skin, dermatology has led the charge in using light therapeutically — harnessing red, blue, and even UV light itself to get rid of acne, eczema, and pre-cancerous skin cells. More recently, anesthesiologists started to explore whether green light can be used to dull the pain from migraines and fibromyalgia. More than any other wavelength, though, infrared light appears to have the most therapeutic potential, and advocates claim it can treat everything from arthritis to Alzheimer’s disease.

While it may seem far-fetched that light has all these effects on the body, it begins to make more sense when you think of light as a form of energy. That energy can affect the behavior of the electrons in atoms that are in, well, everything. What we experience as visible light is really just one small portion of what’s called the electromagnetic spectrum, which consists of different wavelengths of energy-carrying photons. This spectrum ranges from radio waves, which are very long, low-energy wavelengths, to gamma rays, the shortest and highest-energy wavelengths. It includes microwaves and X-rays, too.

Image: NASA’s Imagine the Universe

The visible light rainbow (remember ROYGBIV?) sits in the middle of the spectrum. These wavelengths of energy are the only ones that our eyes can naturally perceive, but that doesn’t mean the other wavelengths don’t exist. Red is the longest visible light wavelength, and infrared is the name of wavelengths longer than red. Infrared light is outside of our field of vision, but you can see it with night-vision goggles.

More than any other wavelength, though, infrared light appears to have the most therapeutic potential.

Scientists have discovered that infrared light can penetrate cells and tissues in the body by an inch and a half and heat them up. This has spurred the rise of infrared saunas, which have gained popularity in recent years through endorsements by the celebrity Pseudoscience Squad — Gwyneth Paltrow, Jack Dorsey, Joe Rogan, Tom Brady, and the Kardashian sisters. Manufacturers and proponents of infrared saunas make the classic Wellness™ claim that they “detoxify” the body — and by “detox,” they mean by enabling you to sweat in a special way that purges your cells of heavy metals, calories, and signs of aging. In case it needs saying, sweat is the same no matter how it’s produced, and it does not detoxify the body (the liver and kidneys do). The purpose of sweat is to cool you down when it evaporates off your skin.

While traditional saunas heat up the ambient temperature of the room, infrared saunas heat the cells in your body. Infrared lamps used in incubators for premature babies and in cafeteria heat lamps to keep French fries warm employ the same technology. Because they heat you up from the inside out instead of outside in, infrared saunas run cooler than regular saunas, maxing out at 120 degrees Fahrenheit instead of 200 degrees. This means you might be able to last longer in an infrared sauna than you could in a traditional one. Other than that, there’s really no difference between the two, and the general consensus seems to be that any health effects conferred by infrared saunas likely stem from the heat rather than the light itself.

This is not to say that saunas — infrared or otherwise — don’t have their benefits. There is some evidence, particularly from Scandinavian and East Asian studies, that they may improve circulation and cardiovascular function, reduce pain, and speed up muscle recovery. Regular sauna use is also linked to a longer lifespan, although whether that’s due to the sauna itself or a result of prioritizing relaxation and well-being is impossible to say.

“The mid-infrared light in the sauna is really used more for health, wellness, athletic recovery, possibly increased athletic performance,” says Michael Hamblin, a principal investigator at the Wellman Center for Photomedicine at Massachusetts General Hospital. “There’s some evidence that it helps with all sorts of systemic disorders.”

Notice Hamblin said mid-infrared light, which has longer wavelengths and is the kind of light used in infrared saunas. This is in contrast to near-infrared light, which has shorter wavelengths and is used in infrared helmets — literally a helmet or headset with small infrared lights glued to the inside.

While traditional saunas heat up the ambient temperature of the room, infrared saunas heat the cells in your body.

Hamblin has been researching the therapeutic effects of light, particularly near-infrared light, for decades, and he thinks it can treat everything from muscle pain to Alzheimer’s disease. He says the benefits of near-infrared light aren’t from the heat it provides but how it alters the body’s cells.

“It’s astonishing the number of diseases and conditions you can treat,” he says. “You can use near-infrared for orthopedic things — injuries, arthritis, tendonitis, muscle pain. You can also use it on the head for the brain — for dementia, psychiatric disorders, head injuries. All sorts of disorders of the brain, it’s quite effective.”

Dr. Julio Rojas-Martinez, an assistant professor of neurology at the University of California, San Francisco, who is also studying the effects of infrared light in the brain, admits that the idea is “alternative or underground.” “It’s not mainstream medicine,” he says. But despite its fringe status, he says there is good biological evidence to back up the claims that infrared light can affect brain cells.

Here’s how it might work: Inside every cell in the body are mitochondria that provide energy for the cell. The vast majority of a person’s energy comes from glucose in the food they eat or that’s stored in the body, which the mitochondria turn into chemical energy that can be used by the cell. It turns out that there are also light receptors inside mitochondria that are sensitive to specific wavelengths of light — like near-infrared — and can turn light energy into cellular energy, similar to plants. This process is nowhere near as efficient as converting food into energy, so our cells don’t rely on light to function, but it suggests that certain wavelengths of light can give people a little boost.

Researchers have demonstrated that shining infrared light on both human brain cells and live rat brains increases cellular metabolism, meaning the production and consumption of energy. Other studies have shown that infrared light can increase blood flow in the brain. In Alzheimer’s disease and other neurodegenerative disorders, cellular metabolism is much lower than normal. Cognitive processes like encoding or retrieving a memory take cellular energy, and one theory about Alzheimer’s is that brain cells don’t have enough energy to perform these memory functions anymore. Rojas-Martinez thinks energy from light could help make up the difference, and he’s now testing whether infrared light can increase brain function in people with the disease.

“You ask a patient with Alzheimer’s disease to learn something or to remember something, there’s going to be [an energy] demand on the memory networks,” says Rojas-Martinez. “But maybe that demand will be higher than what the brain can provide as an output. So the idea of the light therapy is to give the cells support so they can maintain the metabolic function.”

Hamblin says his lab has shown in animal models that infrared light “can increase the number of brain cells and also the number of connections they have,” he says. “That was in animals, but we kind of assume the same thing happens in humans. It’s difficult to show, but we sort of assume that.”

This assumption — that an effect in animals will also occur in humans — can be a much bigger problem than Hamblin suggests. So far, almost all of the research on the effect of infrared light on the brain has been done in mice or in tissue cells in a petri dish, which is very different from being done in a human. For instance, scientists have cured Alzheimer’s dozens of times in mice, yet virtually all drugs to treat dementia have failed in large human clinical trials.

Hamblin isn’t put off by this lack of clinical evidence, though. He says it’s just a matter of getting enough money to run the trials, and then infrared light therapy will become more mainstream. “It’s going to happen gradually because the mainstream medical opinion leaders want to see randomized controlled clinical trials for each indication, and that’s going to take some time,” he says.

Rojas-Martinez, on the other hand, isn’t convinced it will work despite his own research into the topic. “The evidence is there and there are enthusiasts around the world who are paying attention to it, but I remain skeptical,” he says. “I am interested in this field, but I think there are lots of questions.”

There may be a biological rationale, but clinical studies to prove that near-infrared light therapy works in humans are still needed. So for now, hold off on buying an infrared helmet. In the meantime, if you’re desperately looking for a health hack that will boost your mood, improve your skin, enhance your cognition, and help you lose weight and live longer, try going for a run.

Optimize Me is an Elemental column exploring (and fact-checking) the weirdest self-improvement trends. It comes out every Tuesday.

Health and science writer • PhD in 🧠 • Words in Scientific American, STAT, The Atlantic, The Guardian • Award-winning Covid-19 coverage for Elemental

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