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Health The shock revelation that light bulbs are wrecking your metabolism Since the 2000s, our light exposure has changed drastically as we make our buildings more energy-efficient. Now, we’re discovering how this may mess with our mitochondria, contributing to diabetes, dementia and more By Graham Lawton 10 August 2026 Red light is missing from much of our lives Emanuel Santos Take a flashlight – the one on your phone will do – turn it on and place the pad of your index finger over the bulb. See that red glow? You might think it’s something to do with blood, but you’d be wrong. It’s 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. “Light is a nutrient,” says Bob Fosbury, who was an astrophysicist at the European Southern Observatory before he turned his attention to the biology of light. That’s obviously true for plants, which use light to make carbohydrates. But it turns out it’s also true for animals and fungi, all of which exploit light in a hitherto unappreciated way. All living organisms – including us – 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. 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. “We lost about 95 per cent of the spectrum,” says neuroscientist Glen Jeffery at University College London. “Suddenly, without warning, boom, the long wavelengths go. And that’s a problem.” 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’t 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. “LEDs are completely dark in the infrared,” says Fosbury. Scott Zimmerman, founder of the lighting company Silas Inc. in New Jersey who collaborates with Fosbury and Jeffery, calls LED light “ultra-processed”, 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. Campfires, as well as candles and incandescent bulbs, emit red light ClassicStock / Alamy Stock Photo 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. “There’s not a single cause, but I do increasingly think that light is the most fundamental and dominant one,” says Fosbury. “And it’s probably the easiest one to solve.” 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 Tiina Karu 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’s cells produce a molecule called ATP. Red light, she found, accelerated this process. Karu’s 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 patchy, but growing, according to John Mitrofanis, 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’s principal energy currency, analogous to cash in an economy. When a cell needs energy to perform a task – say, building new proteins – 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 – a process Fosbury calls “photometabolism”. The exact mechanism by which ATP production is accelerated remains a point of contention, but what’s 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 “21st-century scurvy”, 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. “It’s something that accumulates over a period of time,” says Jeffery. It isn’t 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. “Their mitochondria are being kick-started by the red light,” 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’ 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 slow down age-related cognitive impairment. 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 significantly less likely to develop dementia, though the underlying causes of this relationship aren’t yet fully understood. Mitrofanis, meanwhile, has shown that red light can prevent Parkinson’s in a primate model of the disease. Cancer and cardiovascular diseases, too, have been linked to a lack of daylight. When dermatologist Richard Weller 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 – a proxy for sunlight exposure in general – were less likely to die from cancer and cardiovascular disease. Indeed, says Mitrofanis, the success of red-light therapy may simply be down to correction of a red-light deficiency. “Maybe all this is doing is rescuing processes that have gone awry because we’re inside all the time, getting illuminated with blue light.” The fact that longer-wavelength light speeds up energy production isn’t 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. “Life on Earth has evolved for 4 billion years in sunlight and it’s adapted exquisitely to the properties of sunlight,” says Fosbury. This greenhouse is flooded with pink LED lights, which emit red wavelengths Getty Images/Westend61 One of those adaptations is the ability to harvest and store photons. “The body literally is designed to absorb as much as possible in the infrared,” says Zimmerman. The amount of light energy we take in every day is staggering, he says. “Sunlight is the number one energy input into the body. It’s at least twice, if not three times, as much as food.” Once sunlight enters the body, it scatters, bouncing off cells and organelles repeatedly – perhaps tens or hundreds of times, says Fosbury – 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’s final destination is somewhat random, but occasionally it is absorbed by a component of the electron transport chain. Scientists 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’re 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 – if the building managers will let you. “Even when it [the incandescent bulb] is very, very, very dim, it still produces a vast amount of IR,” he says. There’s 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. A London hospital has created an outdoor ward King's College Hospital NHS Foundation Trust 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 – and shedloads of savings in the form of a healthier workforce. “We can do masses for public health just by bringing back the long wavelengths of light you’re being denied in your office environment,” says Jeffery. “There’s a real need for change,” says Alistair Nunn, director of science at the Guy Foundation in London, which supports research on quantum biology and its applications in medicine. “At the moment, everybody’s going down this road of ‘let’s get lots of LEDs’, but it’s not doing us any good at all.” Low on energy? A new understanding of rest could help revitalise you There is a state of relaxation that few of us spend much time in, but which comes with profound well-being benefits. With healthier ageing, reduced risk of disease and feeling more energised all on offer, here's how to get there There are signs of institutional change, with – appropriately enough – hospitals at the forefront. Studies have shown 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 discharged sooner, 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’s College Hospital in London. “It’s a beautiful building, but there’s absolutely no long-wavelength light in there,” he says. “I said to them, ‘obviously I’m concerned about your patients, but I’m concerned about your staff too.’” The hospital managers took heed and, in May, opened a new six-bed outdoor ward on the roof. Two other London hospitals are considering outside space for their critical care patients, says Jeffery. “I think they’ll follow because they can’t afford not to.” And even if you aren’t a patient in a critical care ward, you can’t afford to risk 21st-century scurvy through a steady diet of ultra-processed light. “You can live your life without red light,” says Jeffery, “but you cannot live healthily without it.”

Hi all, Have found this forum helpful over the last year while completing my self build in Ireland. I am wondering if anyone has advice on the best way to seal Hollowcore ends before pouring the next lift of ICF walls. Currently weighing up a sand and cement mix vs a rockwool plug (both pushed 100mm inside the core). Curious whether there are other better suited options I haven't considered. Thanks Ross

Having owned property of similar age and condition I don't see anything that would greatly concern me. The house probably has minimal foundations, brick corbel plus maybe 100mm concrete if you're lucky, but has lasted over a century including a mix of exceptionally dry summers and very wet winters with what look like minor cracks. I think it's worth getting an SE to look at your specific concerns (the left E pic most notably) but I'd be careful not to get pulled into a lot of expensive remedial work for limited benefit by the first less than scrupulous builder you speak to.

I want to fit a key lock mechanism to a door, ideally want to fit the key lock mechanism without changing the door too much and since the door already uses a tubular mortice latch the solution I reached to is to use a keyed lock door knob or lever handle, example [ https://www.amazon.co.uk/Qrity-Stainless-Entracne-Passage-Lockset/dp/B06XKJHDP6 ]. Pic of the door without the spindle of the tubular mortice latch, the latch seems to be similar to this https://www.screwfix.com/p/smith-locke-chrome-tubular-mortice-latch-64mm-case-45mm-backset/339px and has the same 45mm backset so I won't be using the latch they are providing since it has a larger backset but since my current latch also has 2 extra holes like the screwfix latch, that are correct distance apart so it probably will work with the door knob above. This seems reasonable since this is an interior door and doesn't need to be that strong and would fit criteria of not changing the door too much. But I don't know much about locks and such so want to know if anyone else has experience dealing with these kind of key lock door knobs or levers from amazon that work with tubular mortice latch.

I’m just going to comment on your original/repeated question - How I would approach this: 1. Keep it simple (as a few others have said). I’ve done both approaches, with good reason and the right intent, but the best response and subsequent discussion has come from a very short initial enquiry. You’ve thought a lot about this; one way of cutting it down is write everything down and then get one of the AI tools to summarise your concerns into, say, 3 bullets that you could easily describe in an initial phone call. I wouldn’t expect it to give a finished solution, but this sort of approach can be good at sifting your thoughts. 2. Start with a phone call. You won’t be able to sift the good from bad necessarily, but you’ll get a feel for whether they’re interested and if it’s worth them visiting (or if you’d rather not progress to that stage - I’d want someone I could comfortably talk to). 3. Approach at *least* 3 before arranging one/two to visit (depending on cost/offers/approach - they will vary). Search for local recommendations, local FB groups you may be on/neighbours who have had big building works done etc. 4. Walk them round the aspects that concern you and why - the subsequent conversation will be led by their professional experience (this is why you want to try doing research on the company/person in advance. IMPORTANT: Check companies house (worth doing for any professional service imho). Dead easy to search - google “company / individual name companies house” this will give you an idea of how established the company is, what the finances are like and when you look at the names of the people you can see if they’ve had multiple businesses. This isn’t always a problem, but it helps you understand the risk or how you choose to pay (for example, I’d be less inclined to pay a lot upfront if there are any aspects that concerned me). Based on your post, personally, I would go for an SE assessment, before then seeing where it may take you as to the work required. Depending on how you get on with the SE you may find they have a few recommendations of other professionals they have a positive opinion of. Always get more than one quote (as mentioned earlier). Best of luck

All day at it. Claude's now struggling to find optimisations. So I need to be extra creative on the method rather than the code. 1024 trees on screen kills frame rate. Tricks a plenty needed

If you have imperial spaced icf then you need to hang your plasterboard American style which is horizontal, not vertical.

Solar is in the planning, but very contradictory, just really just says that it should look like it did before, which it can't as none before. They also want ASHP, MVHR, rainwater harvesting etc and 2 EV chargers. Basically, none of the existing barn exists due to very shallow founds which we replaced and walls converted from single skin to cavity. Planning guy came round one day and said fine, carry on. BC is just concerned with the BC bits and architect has lost interest. That said, it does look like it did before, blocks with openings. It won't as we are having render and cladding, all approved. I think the planning just didn't want anything bigger or higher. Most of the current roof has been removed and the rest will in due course.

That's absolutely what I would do... if it wasn't my profession already. The reason I say that is that even a very good building surveyor (not a quantity surveyor) who is RICS, or the most practical registered Architect will see the cracks and tell you that there are cracks. And that you need an SE to look into it. The AI suggestion above will include both the surveyor or Architect and then the SE. Surveyors and Architects are much better at self publicity, hence AI has found this ready made suggestion.

Yeah we had to submit a NMA for this, no problem getting it approved but an annoying hoop to jump through plus the cost of application

Ours were EPS filled. Worth mentioning you can buy all the bits from Eurocell and make them up to size yourself, which may save a bit although I don't think they were too badly priced ready made.

The other thing if the panels aren't on your plan is it legal to install them. Your planning documents are a legal document for you to follow once approved. Do a variation showing the roof full of solar.

For our Nudura build, we screwed directly to the 8" c/c plastic webbing in the ICF - yes a pain for metric boards, but nothing's fallen off 😉 I posted a a video and photo of hot knifing the channels and fitting plastic conduit (although if you pay a little extra for the low smoke cable, no conduit is required) https://forum.buildhub.org.uk/topic/38949-fitting-conduit-in-eps/?do=findComment&comment=558991

You seem keen to get a report from a SE. Most will deal with this competently. Let us know what they say.

What suprised me were the channels in the formers were not filled with foam, just air gaps. I understand pvc windows are like this but I expected eps within the closers having used the off the shelf ones before. They have a bba cert so they must be good for their stated performance.

As @torre the premade ones are so much better than the off the shelf jobs. I've used them before wouldnt mess about any other way on 150mm cavity construction. To answer your actual question they are stable enough for the brickies to build in as they go. You may find for doors they will set a profile or straight edge up the reveal also.

Max rating of the pipe. I didn't check before I sent it but I thought generally the plastic pipe makers were ok upto 80/90C. You wouldn't want to run like that* but they need to be able to stand behind the product if someone does. * Older hospitals, hotels, etc, often have very hot loops and mix down near the consumers.

I refer the honourable gentleman to the answer i gave some moments (weeks)ago. Listen to what @Nickfromwales said, There is a much cheaper option than CVC for it.

Is it worth approaching your planning department as, with your new solar panels, it will be most certainly NOT like-for-like. Given that all local councils like to big-up their green credentials then an amendment/new planning application might allow you to consider other, less expensive, material choices Regards Tet

Double glazing at 1.2Ug, isn’t bad at all but expected Ug now for double glazed. I can only suggest getting a system that can handle the weight.

Factory glued but also done on site when required, as sometimes you need to fix through the frame and glass needs to be supplied loose.

Do the installers glue the unit in when window fitted then or do they come factory glued?

You get £1 from them and whatever the utility company pay, so for us £1.12 per kWh

They need to tie in to your meter, they also tie into your battery/inverter so they can automate everything. But also provide an API for home assistant app and a setup guide for home assistant also. If you want a referral code to get £25 https://vpp.axle.energy/landing?ref=R-VYFYIHBL

We have our bedroom window open until heating season, then it's closed. But being in Scotland we have to CO2 monitor in our bedroom, it records and gives peak and average readings. I used it tune flow rate to bedroom with bedroom door closed also. So we kept CO2 level at a low but sensible level. Once set there is no need to continually monitor and react.