Recharge Your Life With Light

We were built for a rhythm of light

For most of human history, our relationship with light was pretty simple. The sun came up. Our days were bright. The sun went down. Nighttime was dark.

Modern life has changed that dramatically. We wake indoors. Drive in a car. Work indoors. Exercise indoors. Come home and turn on the lights. Then we add televisions, computers, tablets and phones until shortly before we go to sleep.

Our days have become surprisingly dim. Our nights have become surprisingly bright. Our biology hasn't necessarily caught up.

Light entering the eyes provides important timing information to the body's circadian system — a network of biological clocks that helps coordinate sleep and wakefulness, alertness, hormone timing, body temperature, metabolism and many other daily physiological rhythms.

An international group of light and circadian scientists reviewed the evidence and developed recommendations for daytime, evening and nighttime light exposure. Their basic principle is refreshingly simple:

Read the international light exposure recommendations in PLOS Biology →

Your eyes are doing more than seeing

Inside the retina are specialized cells called intrinsically photosensitive retinal ganglion cells, or ipRGCs. They contain a light-sensitive pigment called melanopsin.

These cells help communicate information about environmental light to areas of the brain involved in circadian timing, including the suprachiasmatic nucleus — often called the body's master circadian clock.

In other words, your eyes are helping your brain answer two very different questions: What am I seeing? And: What time is it?

Morning light says something different to the body than evening light. Bright daylight says something different than darkness. This matters because our daily biological rhythms influence far more than sleep — they're involved in alertness, body temperature, hormone secretion, metabolism, cardiovascular physiology, immune activity, digestion, cognition and mood.

Your bright room may not be very bright

Walk into a well-lit kitchen or office. It looks bright. Now walk outside.

Outdoor daylight can reach thousands or tens of thousands of lux. Under very bright conditions, it can approach 100,000 lux. Ordinary indoor lighting may be only a few hundred lux.

Our eyes adapt so beautifully that we often don't appreciate how enormous that difference actually is.

Morning light may be one of the simplest ways to recharge

This is where I want to keep things practical.

You don't need another supplement. You don't need an expensive light panel. You don't even need to understand melanopsin.

Step outside. Have your coffee outside. Walk the dog. Take a morning walk. Sit on the porch. Open the shades while you're getting ready.

You don't need to stare at the sun. In fact, don't. Simply allow normal outdoor daylight to reach your eyes.

There isn't one perfect prescription — 10 minutes on a cloudy winter morning in Buffalo isn't the same light environment as a clear winter morning in Florida. Season, latitude, cloud cover, time of day and weather all matter.

Tonight's sleep may start with today's light

We tend to start thinking about sleep at bedtime. Circadian biology tells us to start much earlier.

The light your eyes encounter throughout the day helps reinforce the difference between biological day and biological night.

Expert recommendations for healthy adults on regular daytime schedules suggest:

• At least 250 lux melanopic EDI at the eye during the daytime
• No more than 10 lux melanopic EDI during the three hours before bedtime
• No more than 1 lux during sleep

Daylight is preferred for daytime exposure when available. You don't need to start walking around calculating melanopic EDI — the numbers simply bring us back to the same big idea: bright days, dim evenings, dark nights.

There is even evidence suggesting that greater daytime light exposure may make us somewhat less sensitive to unavoidable evening light. That's fascinating because it changes how we think about sleep hygiene.

Want to go deeper on the sleep side? Explore my longer guide: Better Sleep: Evidence-Informed Answers →

The windowless office experiment

One of my favorite studies about light didn't take place in a sleep laboratory. It happened at work.

Researchers compared people working in offices with windows with people working in windowless environments. Workers with windows received considerably more light during the workweek. Among the smaller group whose sleep was objectively measured, workers with windows slept approximately 46 minutes longer on work nights.

This was an observational study, so we can't say windows alone caused the difference. But think about the question it raises: Could the room you spend eight hours in affect how you sleep that night?

Later controlled workplace studies have continued to investigate the relationship between daytime light, sleep and cognitive performance. Maybe our sleep environment begins long before we walk into the bedroom.

Why certain climates and seasons can feel so different

This is the question that started my interest in all of this. Science can't tell me that light was solely responsible. Moving somewhere sunnier can change many things at once — we may spend more time outdoors, walk more, be around more nature, socialize more.

But we also know that light interacts with circadian and neural systems involved in alertness and mood. And we already have a powerful clinical example: bright light therapy is an established treatment for winter-pattern seasonal affective disorder.

So perhaps the feeling many of us recognize — that we simply feel more alive on a beautiful bright day — isn't entirely in our imagination. Our environment is communicating with our biology.

Your light environment changes with latitude, season, day length, cloud cover, solar angle, weather and time of day. But geography isn't the whole story. Someone living in Florida who rarely goes outside could receive less meaningful daytime light than someone in New York who intentionally gets outdoors.

Sunrise isn't just a dimmer version of noon

Natural light is constantly changing. Its intensity changes. Its spectrum changes. Its angle changes. Dawn gradually becomes bright daylight. Afternoon light changes again. Sunset transitions toward darkness.

Our biology developed within this changing environment. Modern artificial lighting can flatten it. The same kitchen lights may illuminate our homes at 7 AM and 9 PM. The same television may glow at noon and midnight.

But biologically, noon and midnight aren't interchangeable. This is why when we experience light can be just as important as how bright it is.

Not all light is the same

Sunlight isn't one type of light. It contains many wavelengths, and those wavelengths don't all interact with human biology in exactly the same way. This is where light science gets especially interesting.

What about blue light?

Blue and blue-green wavelengths strongly stimulate the melanopsin system involved in circadian signaling. That's why saying "blue light is bad" is too simplistic.

Blue-enriched light is a normal part of daylight. During the day, that's useful biological information. Late at night, strong exposure to those wavelengths can provide a very different signal.

When we're talking about the biological effects of light, we have to consider the wavelength, brightness, timing and duration. Context matters.

What about green light?

Green light has become an interesting area of migraine research. Small studies suggest certain narrow-band green wavelengths may produce less discomfort than other wavelengths in people with migraine, and researchers are investigating whether green light might influence headache symptoms.

It's intriguing. But this is where it's important to separate interesting science from established wellness advice. Green light research is worth watching. It isn't something everyone needs to add to their routine.

Red and near-infrared light: the mitochondria story

Red and near-infrared light bring us into a different area of research called photobiomodulation, often shortened to PBM. This isn't the same thing as morning light and circadian signaling.

Photobiomodulation looks at what happens when specific wavelengths of light interact with biological tissues. Researchers are studying effects involving mitochondrial metabolism, nitric oxide, blood flow, cellular signaling, inflammation and tissue repair. One proposed mitochondrial target is an enzyme called cytochrome c oxidase, though scientists continue to investigate other mechanisms.

This is legitimate photobiology. It's also an area where wellness marketing can move much faster than the research.

A 2026 systematic review and meta-analysis looking at photobiomodulation and sleep found a modest improvement in subjective sleep quality across five randomized trials involving 240 participants.

Interesting? Absolutely. Proof that everyone needs a red light panel? No.

Can we eat light?

This may be one of the strangest questions in this entire resource. And I love it.

Plants do something we cannot. They capture energy from sunlight through photosynthesis and convert it into chemical energy. That alone is pretty extraordinary when you stop and think about it.

But there is another area of research that takes the relationship between light and living organisms in an even more interesting direction. Living organisms emit extraordinarily small amounts of measurable light. Scientists usually call this ultraweak photon emission, or UPE. You may also hear the term biophotons.

Plants emit these photons. Animals emit them. Humans emit them. Researchers believe much of this ultraweak photon emission arises from oxidative metabolic processes inside living tissues.

Researchers have measured ultraweak photon emissions from fruits, vegetables and other plant tissues. Those emissions can change with ripeness, stress, storage and the physiological condition of the plant. Scientists are even investigating whether these tiny photon emissions might someday provide a noninvasive way of assessing the quality and physiological state of food.

The Rainbow and the Worm

The late biophysicist Mae-Wan Ho explored an even bigger idea in her book The Rainbow and the Worm. Ho argued that living organisms may be understood not simply as collections of biochemical reactions, but as extraordinarily organized systems in which energy and information operate across many levels — incorporating biology, thermodynamics, electromagnetic phenomena, liquid crystalline organization and concepts of biological coherence.

Physicist Fritz-Albert Popp took the biophoton concept further, proposing that ultraweak photon emissions might participate in communication and organization within living systems.

And this is where the story moves from what we know into what scientists are still trying to understand.

A scientific review published in August 2026 examined this question. The authors concluded that ultraweak photon emission is a real and measurable biological phenomenon, while evidence for a dedicated photon-based communication system remains unproven.

The Farmacy of Light

This is the idea explored in the documentary Farmacy of Light. The film asks a fascinating question: Could freshly harvested, minimally processed food connect us to solar energy in ways we're only beginning to understand?

I think it's a beautiful question. But I also think we need to separate wonder from proof.

Fresh plant foods really do emit measurable ultraweak photons. Those emissions really do change as plant tissues age, experience stress and undergo metabolic changes. What we don't yet know is whether eating those photons provides meaningful biological information or energy to the human body.

So I'm not suggesting that you choose locally grown vegetables because they contain more "biophoton energy." We don't have the evidence to say that. But I love that this research gives us another reason to look at something as ordinary as a freshly picked tomato and realize that it's far more biologically active than it appears.

Eat local and in season

We don't need to wait for the biophoton science to be settled to take something useful from this idea. When you can, eat food grown close to where you live and enjoy foods that are naturally in season.

• Visit a farmers market
• Stop at a roadside farm stand
• Join a CSA
• Grow a few herbs or vegetables yourself
• Or simply look for locally grown produce at your regular grocery store — even larger grocers such as Wegmans work with regional farms and carry locally grown produce when it's available

Local produce may spend less time traveling and in storage. Seasonal produce can be wonderfully fresh. Buying locally connects us with the farms, growers and food systems in our own communities.

Does a tomato picked yesterday deliver more beneficial "light" to your cells than one that traveled across the country? We don't know. And that's where I don't want to turn an intriguing area of biophysics into a health claim that science hasn't established.

But here's what we do know. Plants captured sunlight to grow that tomato. Fresh plant foods provide fiber, vitamins, minerals and an enormous variety of phytochemicals. And eating a diverse diet rich in plant foods has substantial evidence behind it.

Sunlight is more than vitamin D

For years, much of the health conversation around sunlight seemed to come down to one thing. Vitamin D.

Vitamin D is certainly important, but sunlight is a much more complex biological exposure:

• UVB helps initiate vitamin D synthesis.
• UVA participates in other photochemical reactions, including pathways involving nitric oxide.
• Visible light influences our visual and circadian systems.
• Red and near-infrared wavelengths interact differently with biological tissues.

That doesn't mean more sunlight is always better. Ultraviolet radiation is also a well-established cause of skin damage and skin cancer. Healthy light exposure does not mean intentionally tanning or burning.

Your phone isn't the only light in the room

We've become almost obsessed with phones and blue light. Put the phone away. Turn on Night Shift. Buy blue-blocking glasses.

But take a look around your house tonight. There's probably a television. Maybe a tablet or laptop. There are kitchen lights, bathroom lights, overhead LEDs, bedside lamps and possibly nightlights.

Your entire evening light environment matters.

And screens create two different issues. The first is the light itself — a phone held inches from your face isn't the same exposure as a television across the room. Brightness, distance, spectrum and duration all matter.

The second issue may be just as important. What are you doing on the screen?

• Watching the news
• Answering email
• Scrolling social media
• Gaming
• Watching a suspenseful series and letting the next episode automatically begin

Sometimes the problem isn't simply blue light. Sometimes we're just keeping ourselves awake.

Even your nightlight may matter

This is one of my favorite newer pieces of research. A 2026 study measured 25 popular nightlights across 79 settings and found large differences in their potential circadian stimulation.

Two lights that appear similarly dim to us may not necessarily provide the same biological signal — because visual brightness and melanopic stimulation aren't exactly the same thing.

If you need nighttime lighting for safety, keep it dim, low, and away from your direct line of sight. You don't need to turn your house into a cave. We're simply trying to preserve a meaningful difference between day and night.

What is melanopic EDI?

You may start hearing this term more often as light science becomes more mainstream. Traditional lux describes how bright light appears to the human visual system. But our circadian system doesn't respond to every wavelength exactly the same way our visual system does.

Melanopic equivalent daylight illuminance, or melanopic EDI, estimates how strongly a light source stimulates the melanopsin system.

You don't need to measure this every day. The numbers simply bring us back to the same practical idea: bright days, dim evenings, dark nights.

What about light gadgets?

There are some worth knowing about. But here's my rule:

Technology becomes more interesting when climate, work schedules, mobility or lifestyle makes appropriate light exposure difficult.

Start with a lux meter

This is actually one of my favorite light tools because it doesn't promise to fix anything. It teaches you something. Measure your environment first. The free phone apps linked earlier are plenty for experimenting.

10,000-lux light boxes

Bright light therapy has substantial clinical evidence, particularly for winter-pattern seasonal affective disorder. Timing, distance and proper use matter.

Dawn simulators

These are particularly interesting for people who wake up in darkness during winter. Instead of suddenly turning on a bright light when the alarm sounds, a dawn simulator gradually increases the light in the room before waking. The principle has been investigated in controlled studies for seasonal depression and difficulty awakening. Consumer sunrise clocks vary from the equipment and protocols used in research, so don't assume every sunrise alarm clock is clinically validated.

Wearable light glasses

Researchers are studying light-emitting glasses for people such as shift workers who may have difficulty receiving appropriately timed bright light. They're interesting, but most of us probably don't need them if we can simply get outside.

Circadian home lighting

This may eventually be one of the most practical applications of all. Imagine lighting that automatically becomes brighter during the day and progressively dimmer and warmer as evening approaches. Instead of treating people with light, perhaps we start designing our homes and workplaces around human biology.

Red and near-infrared devices

These belong in a different category. Photobiomodulation devices are intended to target particular tissues or biological processes rather than simply strengthening the difference between day and night. Evidence varies substantially depending on the condition, wavelength, dose and device.

Your Recharge With Light rhythm

This is the part I most want you to remember. You don't need to become a light scientist. You just need to become a little more aware of the light around you.

Frequently asked questions about light and health

Sometimes it begins by noticing what's already there

Moving to Florida made me notice light. Science helped me understand why it might matter. But the most important thing I've learned isn't about melanopsin, mitochondria, lux or biophotons.

It's much simpler.

Our bodies live in relationship with our environment. The light outside. The darkness at night. The natural world around us. Even the plants that capture sunlight and eventually become the food on our plates.

Sometimes supporting our health doesn't begin by adding another supplement, device or complicated protocol. Sometimes it begins by noticing what's already there.

Tomorrow morning, step outside. Feel the air. Look at the sky. Move your body. Let the day be bright. Stop at the farmers market. Pick a tomato from your garden. Look for what's local and in season at your grocery store. And tonight, allow things to become darker again.

You don't need to do it perfectly. Experiment. See how you feel.

Explore More

Curious about light? Here are a few great places to listen, read, watch and explore.

Andrew Huberman: Using Light to Optimize Health

A practical look at morning light, circadian rhythms, sleep, mood, blue light and red light.

• Listen to Huberman Lab Essentials
• Free Resource: Using Light for Health Guide

Read: Chasing the Sun by Linda Geddes

An engaging introduction to how sunlight shapes our bodies, brains and daily rhythms.

Read: Life Time by Russell Foster, PhD

The science of our body clocks and their connections to sleep, mood, metabolism and health.

Read: The Circadian Code by Satchin Panda, PhD

A practical look at how light, food, movement and sleep interact with our biological clocks.

Explore: The Rainbow and the Worm by Mae-Wan Ho

A thought-provoking exploration of light, energy, biological coherence and living systems. Some of these ideas remain theoretical.

Watch: Farmacy of Light

A fascinating exploration of sunlight, plants, food and biophotons.

• Watch and explore Farmacy of Light