Take a flashlight 鈥 the one on your phone will do 鈥 turn it on and place the pad of your index finger over the bulb. See that red glow? You might think it鈥檚 something to do with blood, but you鈥檇 be wrong. It鈥檚 photons of red light bouncing around inside your finger, looking for somewhere to land.
This simple experiment is a doorway to one of the most profound and surprising biological discoveries of recent years. 鈥淟ight is a nutrient,鈥 says , who was an astrophysicist at the European Southern Observatory before he turned his attention to the biology of light. That鈥檚 obviously true for plants, which use light to make carbohydrates. But it turns out it鈥檚 also true for animals and fungi, all of which exploit light in a hitherto unappreciated way. All living organisms 鈥 including us 鈥 are solar-powered.
Sunlight has long been understood to be critical to life on Earth. But the fact that light is also used to oil the wheels of metabolism is only just, er, coming to light. Long wavelengths, which come from red and infrared (IR) light, are particularly beneficial for creating energy, and are readily available from sources including sunlight and incandescent bulbs.
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But changes in lighting intended to help save energy have inadvertently deprived us from this crucial supply. The irony is that just as we have discovered the benefit of red light, we are unintentionally starving ourselves of it.
How modern bulbs starved us of red light
The story begins in the early 2000s with the widespread adoption of two now-ubiquitous energy efficiency technologies. The first was the light-emitting diode (LED), which largely replaced energy-guzzling incandescent bulbs. Although this change helped conserve energy, it had other unforeseen consequences. The second was window glass that filters out IR, designed to prevent heat leaking into or out of buildings. Together, these dramatically narrowed the spectrum of light we are exposed to indoors, an environment where most humans spend up to 90 per cent of their time. 鈥淲e lost about 95 per cent of the spectrum,鈥 says neuroscientist at University College London. 鈥淪uddenly, without warning, boom, the long wavelengths go. And that鈥檚 a problem.鈥
For the vast majority of human existence, those long wavelengths of light were unavoidable. Daylight is rich in visible red light, which has wavelengths of about 650 to 750 nanometres. It also emits vast and invisible (to us, at least) quantities of IR, which extends out to about 2500 nanometres.
People who spend much of the day outside are naturally exposed to these long wavelengths, even when fully clothed. When long-wavelength light hits a human body, it sails through clothing and penetrates deep into tissues (short-wavelength light such as UV, in contrast, is absorbed by clothing, which is why covering up helps prevent sunburn). Red and IR are also abundant in moonlight and in the glow of a campfire. Indoor light, too, used to be full of these wavelengths, either from sunlight streaming through windows or light sources such as open fires, candles and oil and gas lamps. The invention of the electric light didn鈥檛 change that, as the spectrum of an incandescent light bulb closely matches that of the sun.
But the adoption of energy-efficient lighting and windows robbed us of longer parts of the spectrum. Glass that filters out IR obviously blocks that portion of sunlight, and while LEDs throw out a lot of visible light, they produce nothing beyond about 750 nm. 鈥淟EDs are completely dark in the infrared,鈥 says Fosbury. , founder of the lighting company Silas Inc. in New Jersey who collaborates with Fosbury and Jeffery, calls LED light 鈥渦ltra-processed鈥, an analogy with ultra-processed food. The combined effect of ultra-processed light and modern glass means that the average human today receives much less long-wavelength light than their ancestors did.
At the same time, conditions such as obesity, type 2 diabetes, dementia and early-onset cancers are on the march. The usual suspects for this are poor diet and lack of exercise. But according to Fosbury, Jeffery and others, these are only a piece of the puzzle; another reason, perhaps the principal one, is red-light deprivation. 鈥淭here鈥檚 not a single cause, but I do increasingly think that light is the most fundamental and dominant one,鈥 says Fosbury. 鈥淎nd it鈥檚 probably the easiest one to solve.鈥
To understand why light is so vital, we have to go back in time again, to the Soviet Union of the late 1980s, where, at the USSR Academy of Sciences in Moscow, a biophysicist called was experimenting with red and near-infrared light as a therapy. She discovered that they were useful in wound healing and pain management and wondered what the mechanism was. Eventually she hit on energy metabolism, specifically the pace at which mitochondria inside the body鈥檚 cells produce a molecule called ATP. Red light, she found, accelerated this process.
Karu鈥檚 work never found a wide audience, mainly because she came from the wrong side of the Iron Curtain, according to Jeffery. But she was right, and today red-light therapy is everywhere, used to promote wound healing and treat skin conditions, hair loss, cognitive impairment, chronic pain, osteoarthritis and much more. The evidence of its efficacy is , according to , a neurologist at the University of Grenoble Alpes in France. There is much debate over the correct doses and wavelengths, but researchers are in agreement that its effects are mediated by mitochondria.
The key to this is the electron transport chain, a complex and highly orchestrated metabolic process that takes in energetic electrons and passes them down a chain of proteins, creating ATP in the process. ATP is biology鈥檚 principal energy currency, analogous to cash in an economy. When a cell needs energy to perform a task 鈥 say, building new proteins 鈥 it uses ATP.
When mitochondria are bathed in red or IR light, the electron transport chain runs a little faster and more ATP is produced 鈥 a process Fosbury calls 鈥減hotometabolism鈥. The exact mechanism by which ATP production is accelerated remains a point of contention, but what鈥檚 certain is that diseased cells are often short of ATP, so a boost can make up the deficit. That, says Jeffery, explains why red-light therapy is beneficial.
It also explains why taking away red light can be harmful. Jeffery points out that all life on Earth evolved in an environment rich in red light and IR, but humans now mostly live in one stripped of those wavelengths. The result is more sluggish ATP production. To add insult to injury, we have also flooded our indoor environment with shorter wavelengths in the form of blue light from screens and LEDs. Blue light inhibits ATP production by slowing down the electron transport chain. Lose, lose.
The effects are insidious. Fosbury likens long-wavelength light to a vitamin and calls the effects of deprivation 鈥21st-century scurvy鈥, a nod to the disease of vitamin C deficiency that killed and sickened tens of thousands of sailors in the 18th century. Like scurvy, it creeps up on you. 鈥淚t鈥檚 something that accumulates over a period of time,鈥 says Jeffery.
It isn鈥檛 just the general benefits of being outside, but red light specifically that is proven to have benefits. One of the symptoms of 21st-century scurvy is elevated blood sugar, which, if left unchecked, can progress to type 2 diabetes. This is due to the slowing down of the electron transport chain, which burns glucose as its primary fuel. A couple of years ago, Jeffery showed that a 15-minute burst of red light blunts the blood sugar spike after a large dose of glucose. He has also done real-world experiments in windowless, LED-illuminated offices at University College London. When he added long-wavelength light from a dimmed incandescent bulb, he found that the office occupants had lower blood sugar, on average, than their colleagues labouring under pure LED light. 鈥淭heir mitochondria are being kick-started by the red light,鈥 says Jeffery. A study published in January found something similar; researchers at Maastricht University in the Netherlands exposed 13 individuals with type 2 diabetes to 4.5 solid working days of LED light in an office environment, then 4.5 days of natural light in the same location. The participants鈥 blood sugar control was much better during the daylight days.
Jeffery also has concerns about other diseases and health problems usually associated with ageing, especially neurodegenerative conditions. One of the causes of these, he says, is mitochondrial dysfunction, which is effectively induced by red-light deficiency. Clinical trials have found that near-infrared light can . A recent study of almost 88,000 people in their sixties found that, over the course of eight years, those who spent more time in daylight were , though the underlying causes of this relationship aren鈥檛 yet fully understood. Mitrofanis, meanwhile, has shown that red light can .
Cancer and cardiovascular diseases, too, have been linked to a lack of daylight. When dermatologist at the University of Edinburgh, UK, and his colleagues analysed data from more than 400,000 adults in a yet-to-be-published study, they found that people with higher habitual UV exposure 鈥 a proxy for sunlight exposure in general 鈥 were .听
Indeed, says Mitrofanis, the success of red-light therapy may simply be down to correction of a red-light deficiency. 鈥淢aybe all this is doing is rescuing processes that have gone awry because we鈥檙e inside all the time, getting illuminated with blue light.鈥
The fact that longer-wavelength light speeds up energy production isn鈥檛 a happy accident. Fosbury and Jeffery argue that it is a design feature of living systems. Life, they say, evolved to feed off this once-abundant resource to maximise the efficiency of ATP production. 鈥淟ife on Earth has evolved for 4 billion years in sunlight and it鈥檚 adapted exquisitely to the properties of sunlight,鈥 says Fosbury.
One of those adaptations is the ability to harvest and store photons. 鈥淭he body literally is designed to absorb as much as possible in the infrared,鈥 says Zimmerman. The amount of light energy we take in every day is staggering, he says. 鈥淪unlight is the number one energy input into the body. It鈥檚 at least twice, if not three times, as much as food.鈥
Once sunlight enters the body, it scatters, bouncing off cells and organelles repeatedly 鈥 perhaps tens or hundreds of times, says Fosbury 鈥 until it hits a molecule that can absorb it, dumping energy in the process. This scattering means that a photon of red or IR light remains inside the body for much longer than it would if it passed straight through. This is what you see when you press your fingertip to a flashlight.
The photon鈥檚 final destination is somewhat random, but occasionally it is absorbed by a component of the electron transport chain. 女生小视频s are currently evaluating whether water molecules in the mitochondria are key to converting light into energy. When they absorb energy from a photon, they vibrate faster and lubricate the passage of electrons down the chain. Remarkably, says Fosbury, each step in the chain requires the electrons to overcome an energy barrier of roughly 0.75 electron volts, which is almost precisely what a photon of long-wavelength light delivers. Without the supply of red light we evolutionarily developed for, we鈥檙e getting far less energy.
Seeking out more red light exposure
Fortunately, the solution to this modern-day scourge is simple: recharge your light battery whenever you can, either with daylight or an incandescent bulb. There are red-light therapy devices, but some of these are overpowered, which can send cellular energy production into overdrive and lead to inflammation. Of course, exposing yourself to sunlight also carries its own risk. But clothing and sunscreen help block cancer-causing UV, while letting red and IR through.
For people stuck in modern offices, Jeffery recommends buying a light fitting with a dimmer switch and putting it on your desk with an incandescent bulb in it 鈥 if the building managers will let you. 鈥淓ven when it [the incandescent bulb] is very, very, very dim, it still produces a vast amount of IR,鈥 he says. There鈥檚 no specific magic wavelength and so a red LED light would likely be better than no red light at all, but nowhere near as effective as full-spectrum red light from incandescent light bulbs or the sun.
What would really make a difference, says Jeffery, is a change in attitude among the people who design and manage modern buildings. The pursuit of energy efficiency is laudable but has unintended negative consequences. And in any case, energy efficiency need not be sacrificed. True, incandescent bulbs are extremely inefficient as a source of visible light, producing mostly infrared, aka heat. But the energy consumption of a heavily dimmed incandescent bulb is no more than an LED, so there are no extra costs 鈥 and shedloads of savings in the form of a healthier workforce. 鈥淲e can do masses for public health just by bringing back the long wavelengths of light you鈥檙e being denied in your office environment,鈥 says Jeffery.
鈥淭here鈥檚 a real need for change,鈥 says , director of science at the Guy Foundation in London, which supports research on quantum biology and its applications in medicine. 鈥淎t the moment, everybody鈥檚 going down this road of 鈥榣et鈥檚 get lots of LEDs鈥, but it鈥檚 not doing us any good at all.鈥
There are signs of institutional change, with 鈥 appropriately enough 鈥 hospitals at the forefront. have that infrared light in hospital wards leads to improved clinical outcomes, including shorter stays. And it has long been known that inpatients who have access to daylight are , on average, than those kept in windowless rooms. Now, some hospitals are taking action. Jeffery and his team recently did a light survey of the critical care unit at King鈥檚 College Hospital in London. 鈥淚t鈥檚 a beautiful building, but there鈥檚 absolutely no long-wavelength light in there,鈥 he says. 鈥淚 said to them, 鈥榦bviously I鈥檓 concerned about your patients, but I鈥檓 concerned about your staff too.鈥欌 The hospital managers took heed and, in May, opened a new . Two other London hospitals are considering outside space for their critical care patients, says Jeffery. 鈥淚 think they鈥檒l follow because they can鈥檛 afford not to.鈥
And even if you aren鈥檛 a patient in a critical care ward, you can鈥檛 afford to risk 21st-century scurvy through a steady diet of ultra-processed light. 鈥淵ou can live your life without red light,鈥 says Jeffery, 鈥渂ut you cannot live healthily without it.鈥
