Health influencers have finally moved on from blitzing green juices and performing squats.
Across social media, the posts receiving millions of views are now far more likely to show an LED light bulb being unscrewed and switched for an old-fashioned incandescent version.
‘I just received my box of flicker-free circadian-friendly light bulbs,’ enthuses one. Others suggest swapping ‘government bulbs’ for ‘freedom bulbs’… ‘unless you want the constant headaches, anxiety, eye strain, disrupted sleep, brain fog, hormone disruption, and that wired but exhausted feeling’.
LEDs (light-emitting diodes) in the home and at work are being blamed for everything from diabetes to certain cancers. It sounds far-fetched but emerging scientific evidence suggests there may be an element of truth to all this.
Incandescent bulbs, developed in the 1800s, produce light when an electric current heats a thin tungsten filament, which heats up and glows – but this wastes 90 per cent of the energy used through heat.
So in 2009, under an EU directive to cut carbon emissions and save energy, the government began phasing out traditional incandescent bulbs, with a full ban from 2016 (although, if you can find them it’s not illegal to buy or use them).
Slowly homes, hospitals, schools and workplaces made the switch to LEDs.
These bulbs require far less power (90 per cent less electricity than incandescents) and tend to last longer while costing roughly the same per bulb.
Rachel Mitchell, 48, had no health issues until in 2021 – when she changed her light bulbs at home to LEDs, got a new LED computer monitor and her husband brought home an LED TV
Left: An LED light bulb, which produces light through a process called electroluminescence. Right: An incandescent bulb, which produces light when an electric current heats a thin tungsten filament
They mainly emit short-wavelength blue light, ranging from 400 to 500 nanometres (nm), which tends to be a harsher, brighter light. Studies agree this increases alertness, and can delay sleep and affect blood-sugar levels.
Meanwhile the high-energy, inefficient incandescents lauded online are a source of red and infrared light – with red emitting long wavelengths of light ranging 600-700nm, and infrared 700-2,500nm – which we also get naturally from sunlight.
This is the key to its acknowledged benefits.
‘An incandescent light bulb roughly puts out a similar spectrum of light as the sun, although you don’t see most of it,’ explains Glen Jeffery, a professor of neuroscience at University College London.
‘An LED light only puts out visible light – but no deep red or infrared which we need to keep our cells functioning effectively.’
He adds: ‘The problem is we spend over 90 per cent of our time in the built environment. Most people have LEDs in their homes and workplaces – and they are completely overpowered by the influence of them.
‘Bear in mind windows filter out infrared light, too. As a result, we are receiving a lot less long-wave light than our ancestors.
‘The effect of this on our health is cumulative over time,’ he adds. ‘We can keep the LEDs for generating light economically in places but we need a different light form for physiological health.’
Science is only beginning to reveal just how vital this long-wavelength light is for health, but studies have linked low exposure to type 2 diabetes, anxiety, skin ageing, obesity and cancer.
How LED light affects us precisely is also still unclear.
Professor Jeffery points to evidence that suggests it affects the mitochondria – the ‘batteries’ in cells that provide energy.
This potentially has knock-on effects across the board.
For instance, research has shown that LED lighting can affect how we metabolise sugar. In a 2024 study in the Journal of Biophotonics, Professor Jeffery and his team showed that a 15-minute burst of red light significantly reduced participants’ blood-sugar levels after a large intake of glucose.
In another study by Maastricht University in the Netherlands, published last December, 13 people with type 2 diabetes spent four days working in an LED-powered office, then another four days working under natural light in the same location. Under the latter, their blood-sugar levels were more stable.
‘The biology is very strong,’ says Professor Jeffery. ‘The absence of infrared light in an LED is definitely associated with pre-diabetic states and a general decline in mitochondrial function – which translates as a decline in metabolic health.’
Could LEDs also affect our body clock? Russell Foster, a professor of circadian neuroscience at the University of Oxford, says it’s complicated, but essentially blue light in the evening in a domestic setting will increase alertness and, if seen long enough, will shift the clock.
But it’s not as simple as blue light is ‘bad’ and red is ‘good’.
‘LEDs have an important role in producing bright light under certain circumstances – for example, in the working environment when you need to promote alertness,’ says Professor Foster. ‘Where you need to be a bit more careful is when using bright light for a long duration in the evenings.’
Professor Foster uses a combination of LEDs in his office in the day and a ‘lovely old-fashioned lamp’ with a LED red-enriched light bulb in the evening.
While many of us may not notice much of a difference from one light bulb to the next, for others it can be stark.
Rachel Mitchell, 48, a former management consultant, had no health issues until in 2021 – when she changed her light bulbs at home to LEDs, got a new LED computer monitor and her husband brought home a huge new LED TV.
‘Within a fortnight, I started getting a pressure sensation behind my eyes – like a vice around my head,’ says Rachel, who lives in Cheltenham. ‘It came on when I used the computer.’
She took screen breaks, and tried other tips, including looking out of the window to rest her eyes and staying hydrated. Nothing worked. Painkillers didn’t help.
‘I was passed around eye specialists – they all found nothing wrong with me. No one could explain it.’
Science is only beginning to reveal just how vital this long-wavelength light is for health, but studies have linked low exposure to type 2 diabetes, anxiety, skin ageing, obesity and cancer
Rachel now stockpiles incandescents she finds online, searching for lighting suppliers’ old stock or bulbs decommissioned from industrial use and hunts for them in antique shops
One ophthalmologist suggested an antidepressant would help with the migraines but Rachel didn’t feel that was right if she wasn’t depressed.
Then after reading about it online, she started experimenting, switching her home LEDs back to incandescent light bulbs.
She says: ‘I found if I stopped using screens and my smartphone I felt better – and if I spent time in bright LED light I got worse, sometimes very quickly.’
After a few months Rachel quit her £100,000 job as she couldn’t look at a screen for a long time – even after changing the light bulbs.
Now she works as a baker from her kitchen, under a 1940s chandelier filled with incandescent bulbs, selling cakes at fairs.
She uses an old iPhone 6 (which doesn’t have LED), struggles shopping anywhere other than Waitrose – where the lighting feels gentle, she says – and runs through her children’s school reception until she gets to the older part of the building where the lighting is comfortable.
Rachel stockpiles incandescents she finds online, searching for lighting suppliers’ old stock or bulbs decommissioned from industrial use. She once found a hoard that had been used behind the coloured glass of traffic lights until they’d been switched to LEDs.
She also searches for the bulbs in the lamps in antique shops. Although you can find incandescents online, they tend to be poor quality and don’t last, says Professor Jeffery.
‘Price is not really a factor as the cost is similar to LEDs,’ says Rachel. ‘The problem is the fear that you can’t get another one. The fear that a route to keeping yourself healthy is getting closed off. There is a deep-rooted unfairness in this. I just want to be able to have a choice of light.’
John Lincoln, co-founder of the charity LightAware, which campaigns on the impact of modern lighting, has seen a surge in people concerned about flicker with LEDs (caused by loose connections, incompatible dimmers and failing bulbs).
He says: ‘Lots of people with migraines are very affected by LED lighting and contact us.
‘The issue is we’ve introduced this lighting, which is having all these biological effects, without doing proper research.’
Professor Jeffery says: ‘We don’t know what flicker is doing to the eye. It’s clear it can generate migraines but it is a nightmare to understand biologically.’
Professor Jeffery, who uses incandescents in his office, lab and at home, suggests putting a bulb that emits red light in the kitchen, where most people spend a chunk of the day, to ensure you get at least 45 minutes’ exposure to long-wavelength light.
‘You don’t have to be religious about it, but they need to be somewhere. Or get a dog – so you have to get out into the sunshine more!’
