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We’ve been taught to think about health in terms of what we eat, how much we move, and even what supplements we take. We have an endless number of tools and devices tracking everything — our steps, our sleep, our heart rate — giving us data around the clock. But one of the most powerful influences on our biology is something we’re barely paying attention to — something we’re exposed to every single day, yet rarely think about.
Light.
Sunlight is one of the primary signals that tells your body how to function. It helps regulate your hormones, your metabolism, your sleep-wake cycles, your mood, and even how your cells produce energy.
“Sunlight is one of the primary signals that tells your body how to function.”
And yet, in modern life, it’s one of the most overlooked pieces of the health conversation. It’s often treated as a nice-to-have rather than an essential part of how we function and feel.
And that’s not entirely our fault. We’ve spent years being told to avoid the sun and protect ourselves from its rays, without fully understanding what happens when we remove one of the body’s most important inputs. And if we’re being honest, many of us are getting more “light” from our phones than we are from being outside.
From an applied quantum biology perspective — which explores how light, energy, and magnetism interact with the body — light is essential. It may be one of the most foundational inputs your body relies on for proper function.
Light is how your body tells time
Before your body can regulate hormones, metabolism, sleep, or energy, it has to know what time it is. That information doesn’t come from your calendar, your phone, or your alarm clock. It comes from sunlight.
“Before your body can regulate hormones, metabolism, sleep, or energy, it has to know what time it is.”
There’s a small region in the brain called the suprachiasmatic nucleus, or SCN. You can think of it as your body’s master clock. It receives signals directly from light entering your eyes and uses that information to coordinate your internal rhythms over a 24-hour period.
This is what drives your circadian rhythm.
Morning light helps signal cortisol to rise in a natural, supportive way so you can wake up and feel alert. This is one of the simplest ways to support your energy for the entire day — stepping outside within the first 30 to 60 minutes of waking, even for a few minutes, can help anchor that rhythm.
As the day goes on, your body uses those same light signals to regulate energy, digestion, and focus. Spending time outdoors during the day — even brief moments between meetings for a short walk — continues to reinforce those signals in a way indoor lighting simply can’t replicate.
As light fades, melatonin begins to rise, preparing your body for rest, repair, and sleep. What’s important to understand is that sunlight doesn’t create melatonin in the moment—it helps your body produce it later. When your brain receives strong light signals during the day, it’s better able to release melatonin at the right time at night. In a way, you’re building your sleep during the day.
“When your brain receives strong light signals during the day, it’s better able to release melatonin at the right time at night.”
This rhythm influences far more than sleep. It plays a role in blood sugar regulation, hormone signaling, immune function, and even how your cells produce energy.
Your body is constantly asking: What time is it, and what should I be doing right now?
Light is what answers that question.
We’re living in a constant state of artificial dusk
The challenge is that our modern environments and even schedules don’t reflect the light patterns our biology was designed for.
Many people spend close to 90% of their time indoors. And while indoor spaces may feel bright to us, they’re actually very dim compared to natural daylight.
“While indoor spaces may feel bright to us, they’re actually very dim compared to natural daylight.”
Even a well-lit room might provide a few hundred lux of light. Outside, even on a cloudy day, light exposure can reach into the thousands. From a biological perspective, your whole body can feel that difference.
Many of us start our mornings staring into a phone screen, then move through a full day under artificial lighting, only to spend our evenings in front of bright screens that feel jarring to our internal clock.
We’re getting too little natural light during the day and too much artificial light at night. Over time, this creates mixed signals for the body. It can look like struggling to wake up in the morning, feeling a mid-afternoon crash, or being tired all day but wired at night. It can look like sleep that feels light or unrefreshing, even when you’re technically getting enough hours.
“We’re getting too little natural light during the day and too much artificial light at night.”
When your body isn’t receiving clear signals about when to be alert and when to wind down, it has a much harder time regulating itself.
We’ve vilified the sun (and lost the context)
Somewhere along the way, the conversation around light became overly simplified.
Sun exposure became something to fear. And while it’s important to be mindful of overexposure — especially during peak UV hours — we lost an important piece of context along the way.
“Not all light is the same. And not all sun exposure is harmful.”
Not all light is the same. And not all sun exposure is harmful.
In fact, appropriate sun exposure plays a meaningful role in human health. It supports vitamin D production, which is involved in immune function, bone health, and mood regulation. It influences nitric oxide release, which supports vascular health and blood pressure regulation. It helps regulate circadian rhythm, which affects everything from sleep to metabolism to hormone signaling.
There’s also something unique about the light we get at sunrise and sunset. During these times, the angle of the sun changes the wavelengths that reach us, increasing the presence of red and near-infrared light. These wavelengths are associated with cellular repair, mitochondrial function, and nervous system support.
It’s part of why so many people intuitively feel calm watching a sunset. There’s physiology behind that feeling.
The issue isn’t the sun itself. It’s how, when, and how much we’re exposed to it. Your body isn’t just responding to light or no light — it’s responding to the timing, intensity, and type of light it receives.
“The issue isn’t the sun itself. It’s how, when, and how much we’re exposed to it.”
When we remove these natural patterns, or replace them with constant, artificial lighting, the body loses some of its ability to regulate these rhythms efficiently. And over time, that disconnection from natural light cues can start to show up in how we feel — our energy, our sleep, our mood, and our overall sense of stability.
You need sunlight for more than vitamin D
Vitamin D is often the only benefit of sunlight that gets discussed, but it’s just one benefit of many.
Yes, sunlight is one of the most efficient ways for the body to produce vitamin D, and adequate levels are associated with immune health, bone density, and reduced risk of certain chronic conditions.
But sunlight also supports health in ways that are independent of vitamin D.
For example, nitric oxide release from sunlight exposure has been shown to support cardiovascular health and blood pressure regulation. Light exposure also influences serotonin production, which plays a role in mood and emotional stability.
“Nitric oxide release from sunlight exposure has been shown to support cardiovascular health and blood pressure regulation.”
There’s even emerging research suggesting that sunlight may influence immune regulation and inflammatory pathways beyond what we can explain through full spectrum vitamin D alone.
This is why supplementation doesn’t fully replace sunlight.
You can support vitamin D levels with a supplement or certain foods, but you’re not recreating the full spectrum of signals the body receives from natural light.
Light as therapy: What we’re starting to use clinically
As we better understand how light interacts with the body, we’re starting to use it more intentionally in clinical settings.
Red and near-infrared light therapy, often referred to as photobiomodulation, is being studied for its role in supporting mitochondrial function, reducing inflammation, improving tissue repair, and aiding recovery. Bright light therapy has been used for years to support seasonal affective disorder (SAD), circadian rhythm disorders, and mood regulation by helping reset the body’s internal clock. Infrared saunas are another example. They use wavelengths of light — primarily in the infrared range — to support circulation, detoxification, and cellular recovery. While they don’t replace natural sunlight, they can complement it by supporting some of the same pathways, particularly around recovery and metabolic health.
“These tools are most effective when layered on top of a foundation of natural light exposure — not as a replacement for it.”
That said, these tools are most effective when layered on top of a foundation of natural light exposure — not as a replacement for it. At Love.Life, we’ve been thoughtful about incorporating these modalities — from infrared saunas that include near, mid, and far infrared wavelengths, to red light therapy beds used for recovery and cellular support.
One of my favorite small shifts at home is swapping bathroom night lights for red bulbs — so those middle-of-the-night pit stops don’t disrupt our circadian rhythm.
When (and how) to work with light throughout the day
Once you understand that light is a signal, the next question becomes: how do you actually use it?
When I talk to patients about light in my medical practice, I try to keep it simple and realistic. This doesn’t have to be complicated. In many ways, it’s about re-aligning with patterns your body already understands.
Morning: Anchor the day
“It’s about re-aligning with patterns your body already understands.”
Morning light is one of the most important signals for your circadian rhythm.
Within the first 30–60 minutes of waking, getting outside — even briefly — helps set your internal clock. This light exposure supports a natural rise in cortisol, which is what helps you feel awake, alert, and mentally clear.
This doesn’t require direct sun or perfect weather. It works even on cloudy days.
If possible, try to let this light reach your eyes without sunglasses (while still being mindful of comfort and safety). Think of it as telling your brain: the day has started.
Midday: Support metabolism and cellular health
Midday light is where intensity increases — and with it, different benefits.
This is when your body can begin producing vitamin D, depending on your skin type, location, and time of year. Tools like the D-Minder app or circadian tracking apps can help guide you based on your location.
Short, regular time outside during the middle of the day can also support both metabolic and cardiovascular health in ways that indoor living simply can’t replicate.
Late afternoon: Reinforce the rhythm
Late afternoon light helps reinforce the circadian signals you set in the morning.
If your schedule allows, stepping outside again later in the day can help maintain energy levels and support a smoother transition into the evening.
Evening: Protect the wind-down
As the sun sets, your biology expects light exposure to decrease. One small change that can make a big difference is turning off overhead lights at night. Bright lighting above you can feel like midday to your brain. Swapping to eye-level lamps or softer lighting helps signal that the day is ending and it’s time to wind down.
You don’t have to eliminate technology, but you can begin to shift the environment:
- witness the sunset when you can
- dim lights where possible
- swap bulbs for red-toned lighting
- use softer/lower light sources like lamps or candles
- be mindful of screens close to bedtime
For those who do need to be on screens in the evening, small adjustments can help. Blue light–blocking glasses, night mode settings, and screen filters can reduce the intensity of the signal your brain receives.
It’s also not just the light — it’s what you’re consuming under that light. Stimulating or stressful content late at night can increase alertness and cortisol at a time when your body is trying to wind down.
A note on safety and context
Working with light doesn’t mean ignoring safety.
Skin type, geographic location, time of year, and personal health history all matter. The goal is not excessive exposure, especially to the point of burning.
A different way to think about light
Light is easy to overlook because it’s not something we can “add-to-cart.” But your body is constantly responding to it — reading it, interpreting it, and using it to guide how your systems function throughout the day.
“Light is a reminder that some of the most powerful tools we have are already built into our environment.”
In a world that encourages more — more supplements, more routines, more optimization — light is a reminder that some of the most powerful tools we have are already built into our environment.
We just have to start paying attention to them.
Dr. Jaclyn Tolentino is a Board-Certified Family Physician and the Lead Functional Medicine Physician at Love.Life. Specializing in women’s health and hormone optimization, she has been featured in Vogue, The Wall Street Journal, and Women’s Health. As a functional practitioner and a breast cancer survivor, Dr. Tolentino is dedicated to uncovering the root causes of health challenges, employing a holistic, whole-person approach to empower lasting wellbeing. Follow her on Instagram here for more insights.
