Why ‘junk light’ from LED bulbs could make you unwell – and how to reduce the health risks

The wrong lighting can be as bad for you as junk food, raising the risk of obesity, heart disease and certain cancers.

That is the stark warning from former Harvard professor Martin Moore-Ede, a pioneer in the field of circadian biology – the study of the biological “clocks” inside the cells of almost all living things, which follow approximately 24-hour cycles, in keeping with the sun.

Most artificial lighting today, whether from light bulbs or screens, delivers the wrong wavelengths to our brains and bodies, and often at the wrong time, he explains.

And a growing body of laboratory and population research links this exposure to higher rates of breast and prostate cancers as well as diabetes, obesity and cardiovascular disease.

The crux of the problem is that “lighting today is so different from the natural light in which the human race evolved”, the 80-year-old English scientist and lighting consultant tells The Straits Times in a phone interview from Boston, Massachusetts.

“Until about a century ago, we were mostly outside and exposed to daylight, which is a full spectrum that contains ultraviolet, all the colours of the rainbow and, importantly, infrared.”

But instead of replicating that full spectrum, most LED lighting is designed mainly to illuminate, and as cheaply as possible.

The majority of LED bulbs create “an illusion of white light” using a limited number of balancing colours, he says. The light they generate has “a blue spike in it and a lot of yellow and green”, with even bulbs marketed as “warm white” often producing too much of some blue wavelengths.

They also omit the rest of the spectrum, despite each component playing an important role in health. Deep violet light, for instance, supports eye development, while infrared boosts energy production in cells.

The result is lighting designed for vision and energy efficiency, but falling short for overall health.

‘Junk light’ impacts circadian health

“You might call it junk light, and it’s actually analogous to junk food,” Moore-Ede says.

His 2024 popular-science book The Light Doctor – which is available on Amazon in Singapore, with a second edition out in August – breaks down the science and suggests healthier habits around light exposure.

This message comes as circadian science has gone mainstream.

In the last five years, “circadian” has surged as a search term on Google, bolstered by social media wellness trends that began during the Covid-19 pandemic – as people spent more time indoors and scrolling – and has repeat mentions on the popular science podcast Huberman Lab.

But Moore-Ede’s fascination with the subject began decades ago when, after getting his medical degree in London, he moved to Canada and became a surgical resident in his early 20s.

“Working 36-hour shifts as a trainee surgeon under bright fluorescent lights, I got into this brain-scrambled condition, which is part of circadian disruption, or when the clocks in your body get out of sync. That led to fatigue, malaise, difficulty focusing and remembering, and nodding off in the operating room,” he recalls.

Moore-Ede went on to pursue a PhD in physiology at Harvard University and make a name for himself in the then nascent field of circadian biology.

While he was a professor at Harvard Medical School in the 1970s and 1980s, he led a team that located the suprachiasmatic nucleus, or master biological clock, in the human brain and showed that it was synchronised by light received through the eyes.

That synchronisation regulates multiple processes in the body, including heart rate and digestion, and triggers the release of hormones such as melatonin and cortisol.

But artificial lighting often disrupts both the master clock and the trillions of peripheral clocks throughout the body, and Moore-Ede’s book is packed with examples of the possible downstream effects.

Breast cancer rates in electrified societies, for instance, run far higher than those in populations living mostly by natural light.

Women who are blind from an early age have extremely low rates of this cancer, with similar findings for prostate cancer among blind men. Laboratory studies reveal the likely mechanism, showing that blue-rich light at night suppresses melatonin, a hormone released in darkness.

“If you have lots of melatonin in your blood, that kills cancer cells in the body. But if you have bright LED lights in the evening or at night, it actually switches off the melatonin, allowing cancers to grow,” Moore-Ede explains.

This is one reason the World Health Organization’s cancer research arm designates night shift work as “probably carcinogenic to humans”.

Circadian disruption wreaks havoc on blood sugar and appetite as well, which can lead to difficulty maintaining a healthy weight.

“If you are exposed to blue light in the evening, it creates insulin resistance. Your cells think it’s daytime and do not process glucose as well, so blood sugar and insulin levels climb. And that all leads to an increased risk of diabetes, heart disease and psychiatric disorders,” says Moore-Ede.

Reducing health risks

So what can people do in countries such as Singapore and the United States, where LED lights are now the default, and most incandescent bulbs – which emit far less blue light – are considered energy-inefficient and no longer sold?

If you have to be indoors, Moore-Ede advises spending as much of the daytime as possible near windows that let in natural light. For evenings, he recommends seeking out LED light bulbs producing less than 2 per cent blue light.

Also look for bulbs with a lower, or warmer, correlated colour temperature of 1800K or less.

“You can also have light bulbs with 3000K, provided they are engineered to remove the key sky-blue wavelengths,” he adds.

Late-night screen time is another source of circadian disruption, but however addicted you are to those devices, he strongly advises sleeping in complete darkness.

“Surveys show that 40 per cent to 50 per cent of people, particularly as they get older, leave some light on in the bedroom.

“But people who do that die sooner, and have double the risk of diabetes, heart disease and cancer,” he says.

And regardless of what happens indoors, it is vital to get a robust dose of morning sunlight shortly after waking.

Moore-Ede suggests spending at least 30 minutes outdoors every morning so your eyes get those all-important circadian signals. If your eyeglasses filter out UV and other wavelengths, take them off during this time. Morning light also helps melatonin rise properly at night, ensuring good sleep, and can mitigate UV-induced damage from the sun later in the day.

Through his consulting and research firm Circadian, Moore-Ede helps businesses implement healthier lighting systems, and has worked with hundreds of Fortune 500 companies as well as automakers such as Toyota and Honda.

“And we’ve been able to show that people are more alert on the job and make fewer errors, sleep better and have fewer gastrointestinal problems,” he says.

Inconvenient truths

Asked why the health risks of modern lighting are not discussed more often, Moore-Ede points out that it is an inconvenient subject for manufacturers heavily invested in blue-rich LEDs.

“But the scientists are not confused about this,” he says, citing a 2023 consensus statement signed by 248 researchers, who argued for putting warning labels on blue-enriched LED lights indicating they may be harmful if used at night.

“It just hasn’t got into the general media.”

Individuals, however, can take control of their own light exposure and make better choices.

Moore-Ede practises what he preaches, both in his home and office in Boston, where he has installed light bulbs that automatically change from blue-rich by day to blue-free by evening before turning red at night.

“I follow a healthy light diet because I want to live not just a long life, but a long and healthy life,” he says.

Circadian biology expert Martin Moore-Ede’s top tips for circadian health

1. Prioritise morning light

Spend at least 30 minutes outdoors soon after waking up. Avoid wearing eyeglasses or sunglasses during this time.

2. Seek daylight

If you are indoors during the day, stay as close to windows and natural light as possible.

3. Dim and warm your lights in the evening

Switch to warmer, orange-red lighting after sunset. Look for special bulbs designed with low or zero blue wavelengths.

4. Embrace complete darkness

Turn off or completely block all light sources in your bedroom while sleeping.