Is Your Light Exposure Hurting Your Health?

Last Updated on March 8, 2025

Our bodies are sensitive to light in ways that most of us don’t realize. While the effects of blue light from screens on circadian rhythms is common knowledge now, far less well known is how big an impact other kinds of light exposure can have not just on sleep, but also on energy levels and even on our risk of chronic disease.

Read on to find out about the fascinating research on ways effects the lights we live with every day may be affecting our health.

HOW DOES LIGHT EXPOSURE AFFECT HEALTH?

You’ve probably heard about the negative effects of the blue light emitted by your screens at night. All that blue light from our phones, tablets, and laptops sends messages to our brains that it’s daytime, suppressing melatonin production. That’s not good, since it makes quality sleep much harder to get.

But it turns out, even if we’re diligently putting down our screens at night to protect our circadian rhythms, our lightbulbs might be causing a lot more trouble than we realized.

While working on an article about mitochondrial health recently, I came across some fascinating research on the effects of the light environment we live in and its impact on our mitochondrial function.

A quick refresher in case you’re not familiar with these vital organelles: You may have been told in high school biology that mitochondria are the powerhouses of cells. While true — mitochondria convert the food we eat into the energy we use to do virtually everything — they do so much more.

Because they’re involved with all sorts of cellular processes, mitochondria also play a critical role in numerous functions, including the immune system, hormone production, circadian cycles, and lots more.

Because they affect so many systems in the body, when they’re not working well our health suffers. Research suggests that mitochondrial dysfunction plays a part in cardiovascular disease, neurological and psychological disorders, diabetes, and cancer. The mitochondrial theory of aging posits that the health of our mitochondria helps to determine the length of our healthspan, the period in which we live free of debilitating disease.

And these critically important organelles, it turns out, respond to different wavelengths of light hitting our eyes and skin.

BLUE & RED LIGHT’S EFFECTS ON MITOCHONDRIAL HEALTH

I had the pleasure of speaking with Professor Glen Jeffery, a neuroscientist who researches the effects of different wavelengths of light on mitochondrial health at University College London. His ongoing research has found that the light emitted by LED lightbulbs — yes, the ultraefficient ones we swapped in for more wasteful incandescents in efforts to save energy in recent years — negatively affects mitochondrial health.

Jeffery explained to me that mitochondria, which have existed in symbiotic relationships with multicellular organisms for billions of years, evolved in organisms that until very recently have lived outdoors, where they’re exposed to ample sunlight, which has a balance of blue and red wavelengths. The light of the sun hitting these organisms, it turns out, has profound effects on the ways their mitochondria function.

As you’ve likely heard, modern humans now spend roughly 90% of their time indoors, getting minimal exposure to sunlight. What altered our light exposure even further, Jeffery told me, was the sudden and widespread switch from incandescent lightbulbs to more energy-efficient LEDs, which emit very different wavelengths of light than their less-effecient predecessors.

Like sunlight, the light from incandescent bulbs, Jeffery says, include infrared wavelengths, while LEDs (and fluorescents) do not. Compounding the problem, he explained, modern windows block infrared light to help keep indoor spaces cool.

So in the last two decades, we — and our mitochondria — have been suddenly forced to contend with an entirely different light environment than we evolved to live in.

Jeffery told me that people living and working in buildings lit by LEDs and with infrared-blocking glass are essentially “starved of infrared light,” which he says makes mitochondria function poorly. After billions of years evolving in sunlight with a particular balance of blue and red light, we’re suddenly asking our bodies to adapt to a light environment dominated by blue wavelengths. This diagram shows the range of wavelengths in sunlight as compared to that in an LED if you’re curious.

It turns out scientists can measure the effect of all this blue light on the health of mitochondria, and they’ve found that mitochondria tend to function very poorly when deprived of red wavelengths. Blue light exposure may damage the eyes, disrupt the circadian rhythm, and negatively affect metabolic health.

Mounting research suggests that this lack of exposure to red wavelengths can affect mitochondria all over the body, and when they’re not functioning properly, researchers believe they play a role in metabolic diseases like diabetes and obesity, as well as cardiovascular disease, neurological disorders, even mental health.

Not only that, because our mitochondria are intimately involved with regulating our circadian rhythms, when they’re not healthy, our sleep can also suffer. If you struggle with sleep, you might think about the light you’re exposed to every day. Making your lighting environment more mitochondria-friendly may help improve your sleep, which can have a host of beneficial effects on health as well.

More on how to do that below.

(Good nutrition is also fundamental for healthy mitochondria, so a whole foods, varied diet can also help support mitochondrial function. Here are some foods that help sleep and some antioxidant-rich superfoods to consider eating more often.)

Dr. Jeffery is fascinating to listen to, and you can hear him present his research in a number of interviews he’s done on YouTube, like this one.

WHAT YOU CAN DO TO IMPROVE LIGHT EXPOSURE

Fortunately, Jeffery has researched some simple ways we can make our light environments healthier. The primary thing he suggests is getting more sun. “Go for a walk in park during your lunch break,” he says. “That’s enough.” He notes that even if it’s a cloudy day, the longer wavelengths you’re after will still get through.

There are lots more benefits to spending more time outdoors, so make a point to get outside every day, even for a short stroll.

Indoors, he says people “can counter the effects of blue light by bringing more long wave light into their environment.” He recommends lessening your exposure to the blue light from LEDs and fluorescents where possible. If your workplace is lit by these bluer lights, he says simply adding a lamp with an incandescent bulb can expose you to some beneficial red light.

Though you can find lots of red light therapy products for sale online, he warns that most of them don’t do what they say they do. He’s measured the wavelengths coming from numerous devices sold online and found that most don’t contain the infrared wavelengths our mitochondria work best under.

BRINGING IN MORE RED LIGHT

1. Add incandescents. When our interview finished, I went to the basement store room, where I was pretty sure I’d stowed all the incandescent bulbs we’d replaced in the early 2000s. I found a box filled with them. (Anyone else living green have issues with throwing things away? Moments like this don’t make that easier.)

Though I’m generally all-in on ways to save energy (home solar power, insulation, and heat pumps, for example), in this case I feel that the benefits of a few incandescent bulbs in targeted areas around our otherwise super-efficient house are worth the trade off of a little extra energy use for a significant benefit to our health.

With the many energy upgrades we’ve made over the years, we use so much less energy than average and our electricity is all from solar, so I don’t feel guilty swapping in a few less efficient bulbs.

I put the few 40-watt ones I found in bedrooms and some 60-watt ones in living spaces and here next to my DIY walking desk, where I’m writing now.

We still have several built-in LEDs and LED bulbs in most of the fixtures in our house, so we’re only using more energy for lighting in a few specific places where I want to try what Jeffery suggests, adding in red wavelengths where there currently aren’t any. I’m also trying to favor them over the LEDs in the evening.

Though incandescents are harder to get these days, you can find them if you look carefully. Jeffery advised that if you’re having trouble locating incandescents in your local hardware store, you should still be able to find low-wattage incandescents for appliances (like these), as LEDs would melt in ovens.

I went to see what the nearest home improvement store had, and the pickings were indeed very slim. There were a few larger bulbs meant for vanity lights that don’t fit into table lamps, and some shaped like flames for chandeliers. I got a pack of the wide base 25 watt chandelier lights to try in bedside lamps.

You can also find incandescents for sale online. Just read carefully, as LEDs may also come up in a search.

2. Make the most of light coming in from older windows. Since my 100-year-old house has plenty of older glass, in winter, when it’s too cold to take my work outside on the porch and I spend much less time outdoors, I started working by a window with good light exposure for part of the day.

Jeffery told me that infrared light bounces around quite a bit, so I’d be getting a fair amount sitting nearby, even when the sun wasn’t shining right on the window.

Since UV can penetrate glass, not having the sun shine directly on your skin for hours on end is probably a good idea. Park yourself near the window, but don’t feel like you need to be in the sun to get the benefit of the infrared wavelengths.

CONSIDER A RED LIGHT

While Jeffery recommended getting outside and using incandescent light bulbs, in his own office he has a red light like this one he likes to have on in the morning. In his studies, he’s found benefits to mitochondrial health comes with just a few minutes’ morning exposure. (In the afternoon, interestingly, it doesn’t seem to help.)

I asked him what type of device would work if I wanted to replicate what he does, and he pointed me to this one:

If you’ve been curious about the touted benefits of red light, unlike many pricey devices on the market, this relatively inexpensive device has been tested and verified to contain the wavelengths found to be beneficial for mitochondria.

Jeffery warns, “About 90% of what you see in the marketplace in terms of red light is worthless. Some are unsafe. We bought loads of devices off the web and tested one after another. One or two got close to being doable.”

I hope you found this information on light exposure illuminating 🙂 Stay tuned for more research on this topic, which I’ll be sure to link here. Share it with friends — this info needs to be better known!

I don’t know about you, but when there’s some easy way to improve my health, I’m all for it. I collect my favorite “savvy health hacks” here on HealthyGreenSavvy. A few to check out:

• Immune Boosting Foods
• How to Eat For Better Sleep
• Why You Need a Water Filter
• Easy Health Hack: Sit Less
• Anti Inflammatory Food
• Easy Ways to Reduce Cortisol

Now put aside your device and head outside for some beneficial infrared exposure!

Save this info on healthy light exposure for later!

Photo credits: Cover — TMGZ2021 ; pin — Curtis Adams and Terry Magallanes from Pexels