Same Sun, Different Rules: Sunlight Guide by Skin & Location

Same Sun. Different Rules: Why Your Skin, Geography, and Daily Timing Decide Whether Sunlight Helps or Hurts You

Watch the companion video here: https://www.youtube.com/watch?v=B4za7PHpN8s

TL;DR (for the skimmers, I see you) — It's an 8 minute read btw.

Sunlight does way more than help you make vitamin D. It sets your internal clock, affects your hormones, shapes your sleep, and influences how well you recover. There are three windows that matter: morning (clock setter), midday (vitamin D), and evening (wind-down). Most people are missing at least one.

Your skin type and geography change the math. If you're dark-skinned in a northern city, you're playing on hard mode. If you're pale in a high-UV environment, you can accumulate damage fast without realizing it.

And the part that really sucks? You can do everything right during the day and wreck it with bad light at night.

Track your UV. Test your blood. Stop guessing.

If you want the visuals and examples, watch the video.

The Winter Pattern That Finally Forced Me to Pay Attention

Every winter, I'd get depressed.

Not "a little off" depressed. Flat. Low energy. Tired in a way sleep didn't fix.

And it wasn't just me. My mom dealt with the same thing. So did my sister.

For years I chalked it up to weather. Cold months. Grey skies. Everyone feels worse in winter, right?

But around 2019, I started paying closer attention. Not just to mood, but to light. And the deeper I went, the more it clicked that this wasn't about temperature or motivation.

It was about UVB. Or more accurately, the lack of it.

My family is Nigerian. I've got the 23andMe results to prove it. Total waste of money, by the way. Told me nothing I didn't already know.

My parents were both born in Port Harcourt. Equatorial sun, year-round. My biology expects a level of light that California winters don't deliver.

Once I understood that, I stopped treating sunlight like background noise and started treating it like training.

I changed how I worked. I take my laptop outside whenever I can. I train outside as much as possible. Not just for movement, but for light.

And in winter, when the sun isn't enough, I use light tools to fill the gap.

The result? This past winter was the first time I've ever tested vitamin D levels in the 50s during the cold months. More importantly, winter didn't hit me the way it used to.

I'm not saying everyone can restructure their life around sunlight. Work makes this hard. I get it.

But the difference between some effort and no effort is bigger than most people realize.

This article is the full breakdown. What sunlight actually does, why your skin and location change the rules, and how to stop guessing.

Why Everyone Is Arguing About Sunlight (And Missing the Point)

Sunlight has become a culture war.

One side treats it like poison. DNA damage. Skin cancer. Premature aging.

Bryan Johnson, who is extremely pale and lives in a moderate-UV environment, calls himself a vampire and avoids the sun like it's trying to kill him. For his skin and his context, that caution makes sense.

The other side — let's use Dr. Paul Saladino as an example — treats sunlight like a cure-all and walks around shirtless at noon like consequences don't exist.

Both sides are touching real things. The problem is they're talking past each other because context gets ignored.

I'm not a vampire. I'm a daywalker!

My biology was built for equatorial sun, and I'm living in California, not New York, London, or a LOW UV environment. Bryan's advice doesn't apply to me. And my approach wouldn't work for him either.

Sunlight isn't good or bad in a vacuum. It's dose-dependent.

And that dose depends on your skin, where you live, the time of day, the season, and what you do with light after the sun goes down.

Miss any of those, and generic advice can quietly work against you.

Before Antibiotics, Doctors Paid Attention to Sunlight

Before antibiotics, doctors had to pay attention to what worked.

In the early 1900s, physicians noticed something strange. Patients with tuberculosis, chronic infections, and wounds that wouldn't heal often stalled indoors. But when moved into sunlight, many improved dramatically.

Hospitals across Europe started building outdoor treatment terraces specifically for this.

In Switzerland, Dr. Auguste Rollier used controlled sunlight exposure with remarkable results. Around the same time, Danish physician Niels Ryberg Finsen developed focused light therapy for lupus vulgaris, a form of skin tuberculosis. He won the 1903 Nobel Prize for it.

The insight was simple: light itself can be therapeutic.

We've mostly forgotten this. Instead, sunlight gets treated like a lifestyle perk. Biology doesn't agree.

Why Modern Indoor Life Breaks the Light Signal

Here's the simplest way to explain what's broken.

First, glass blocks UVB.

You can sit in a bright sunlit room all day and still make zero vitamin D. Windows let visible light through, but they filter out the wavelengths your skin actually needs.

Second, indoor lighting is static and mistimed.

Your lights look the same at 7 a.m., noon, and 10 p.m. Your biology does not.

Third, your body evolved with changing light across the day.

Bright, blue-rich light in the morning. Strong overhead sun at midday. Warm, low light in the evening. Darkness at night.

Modern life flattens that pattern. Same light. All day. Wrong timing.

Your body notices.

Why Vitamin D Is Only One Chapter in the Sunlight Story

Most people live the same pattern now.

Building. Car. Building. Car. Building.

Sunlight becomes something you "catch" on weekends.

That's why vitamin D supplements feel like the solution. They're easy.

But sunlight isn't a single input. It's a timed, full-spectrum signal. Different wavelengths. Different intensities. Different effects depending on when they hit your body.

Vitamin D is one part of that signal. It's not the whole thing.

The easiest way to understand this is through three sunlight windows.

The Three Light Windows Your Body Actually Cares About

Morning: The Clock Setter

Morning light is your body's "on" switch.

When light hits your eyes early in the day, it tells your brain it's time to be awake. That signal helps cortisol rise in the morning and starts a timer for melatonin to come up later at night.

Miss this consistently and your rhythm drifts. Sleep gets lighter. Energy flattens. Recovery slows.

You don't need direct sun. Even cloudy daylight works, because it's still far brighter than indoor lighting.

You just need to get outside soon after waking.

Midday: The Vitamin D Window

This is the window most people skip. It's also the one that changed everything for me.

Vitamin D production requires UVB, and UVB is strongest when the sun is high overhead. Morning and evening light are great for your internal clock, but they're often too weak for vitamin D.

For years I was getting morning light, feeling good about my "sun exposure," and still testing low. I wasn't lazy. I just didn't understand that the light I was getting didn't contain what I actually needed.

How long you need depends on skin type, latitude, season, and how much skin is exposed.

Near the equator, usable UVB can show up most of the year. In mid-latitude cities, the window is long in summer and shorter in winter. Farther north, like London, it can shrink to a couple of hours in autumn and disappear entirely in winter.

That's why people say, "I'm outside all the time," and still test low. I was one of them.

Evening: The Wind-Down Signal

Evening light is low in UV and richer in red and near-infrared wavelengths. It tells your body the day is ending.

This window supports relaxation and sleep. It does not make vitamin D.

One thing most modern homes get wrong is overhead lighting. Ceiling LEDs blast light downward like artificial midday. Table lamps, floor lamps, and warmer bulbs keep light lower and softer, which your nervous system reads as "evening."

Here are the red bulbs I use in my home

Same room. Same brightness. Completely different signal.

The Easiest Way to Undo a Good Day of Sunlight

You can get sunlight right during the day and erase the benefits at night.

Blue-heavy indoor light after sunset tells your brain it's still daytime. Melatonin gets delayed. Sleep quality drops. Recovery takes a hit.

The less natural light you got during the day, the more sensitive you are to this at night.

The fix isn't perfection. It's reducing the biggest offenders:

Dim lights after dark
Avoid harsh overhead lighting
Use warmer bulbs, red or amber
Consider blue-blocking glasses at night

I'm not perfect here. My girlfriend and I play Gin and watch Dexter in the evening. Blue light is definitely present. But we've got safeguards in place.

The goal isn't darkness. It's protecting your rhythm enough that sleep actually works.

Why Your Skin and Location Change the Rules

This is where most sunlight advice falls apart.

Melanin acts like built-in UV protection.

That means two things can be true: darker-skinned people can make vitamin D, but they often need more UVB exposure to do it under the same conditions.

Think of it like running a car built for premium fuel on regular. It'll still run. Just not the way it was designed to.

In real life, UVB exposure isn't standardized. Geography matters.

A darker-skinned person living in a northern city may struggle to produce enough vitamin D for large parts of the year. A fair-skinned person living in a high-UV environment can accumulate damage quickly if exposure isn't built gradually.

Same sun. Different biology. Different rules.

When Culture Pushes You Away From What Your Body Needs

Even geography isn't the full story.

Across many cultures, lighter skin is still treated as more desirable. That drives sun avoidance. Covering up in summer. Choosing indoor spaces. Skipping outdoor activity.

Not for health reasons. For appearance.

The result is people who may biologically need more sunlight being conditioned to avoid it.

This isn't a willpower problem. It's social conditioning layered on top of biology.

P.S. This is the part of the youtube video that I really enjoyed talking about. You should really watch the video below.

Sun, Skin Cancer, and the Trade-Offs Nobody Explains Well

Skin cancer risk is real. Burning is never the goal.

Risk depends on skin type and environment. Melanin absorbs UV before it damages DNA, which is why melanoma is rarer in darker skin.

Using sunscreen on darker skin adds another trade-off. You're stacking protection on top of protection, which can make vitamin D production even harder.

There's also a form of melanoma that shows up where melanin doesn't protect at all. Palms. Soles. Nail beds. Bob Marley died from it.

Know the ABCDEs: asymmetry, border irregularity, color changes, diameter, evolving appearance. If something looks off, especially in those areas, don't let it get dismissed.

Dermatologist Ade Adamson has been sounding the alarm on this for years.

On the other side, chronic sun avoidance has costs too. Deficiency. Poor sleep. Immune and metabolic issues.

The real question isn't "is the sun good or bad?" It's whether your exposure matches your biology.

So How Do You Know If Your Exposure Actually Matches Your Biology?

Stop Guessing What "Enough Sun" Means

"I go outside" doesn't mean much without context.

What time? What was the UV index? Did you actually make vitamin D, or just get fresh air?

UV tracking apps help. I use the UV Index App and "Sun Day" App. They pull real-time UV data for your location and estimate how long you need outside based on skin type and clothing.

Clothing matters. A light shirt can significantly reduce UVB exposure.

Rule of thumb: UVB is strongest when the sun is highest, roughly late morning to early afternoon, and when the UV index is 3 or higher. That window changes with location and season.

Why You Can't Feel Your Way Out of Deficiency

You don't feel vitamin D deficiency cleanly.

You feel tired. Flat. Slow to recover.

Unless you test, you'll never connect those dots back to light.

You can ask your doctor for vitamin D labs. If you want more control, I've used Hundred Health and Marek Health. Click here to learn about both, with discounts for The Stronger Human Community.

Hundred is simpler and more affordable with a slick app. Marek is higher-touch with guided interpretation.

This Video dives into my personal lab results from Hundred and a Marek patient care coordinator walks me through my labs.

Test at least once a year. Otherwise you're guessing.

I test twice, but that's because I like to understand my mid-year and winter lab numbers.

Why Supplements Help, but Don't Replace Light

Vitamin D supplements can help when levels are low or UVB access is limited.

If you're taking higher doses, spreading them out and taking them with fat improves absorption. Magnesium and vitamin K2 often come up alongside vitamin D because they help the body handle calcium properly.

But supplements raise a number. Sunlight delivers a system-wide signal.

Sunlight affects blood flow, mood, sleep, and immune signaling in ways pills can't fully replace.

Your skin also has a built-in off switch. Once you've made enough vitamin D from sunlight, production slows down. Pills don't self-limit.

Think of sunlight as the full album. Supplements are one track.

What to Do When the Sun Isn't an Option

If you live in a low-UV environment or work indoors most of the day, tools can help.

Red and near-infrared light support recovery and tissue health. In simple terms, they help the parts of your cells that make energy work more efficiently, especially when they're stressed by modern indoor life.

Red light doesn't make vitamin D. For that, you need UVB.

That's why some devices combine red, near-infrared, UVA, and UVB. The Krypton UV 1612 is the one I use personally in winter, and I've started using it with my mom and sister when the weather doesn't meet their needs.

The Devices I Recommend

The Stronger Human Store features red/NIR panels like the Inferno and Firewave along with Red/NIR+UVA/UVB Panels like the Krypton and Ultron.

Red/NIR, UVA/UVB Devices - Click Here (You can get notified when they're back in stock)
Red/NIR Devices - Click Here

For the Curious: Why Some People Pair Cold With Light

This part wasn't in the video.

Some researchers and practitioners have been exploring the idea of pairing cold exposure with light exposure.

Here's the simplest way to think about it.

Cold exposure forces your body to spend more energy just to maintain temperature. That raises metabolic demand and activates systems related to alertness, stress tolerance, and energy use.

Light does something different. Sunlight especially. It provides timing information. It tells your brain and body when to be awake, when to recover, and how to organize energy across the day.

The hypothesis isn't that cold produces vitamin D or somehow creates light internally. It's that cold may temporarily increase metabolic readiness. So when light exposure follows, your body may be more responsive to that signal.

Cold increases sensitivity. Light provides the instruction.

This is an emerging area. Not settled science.

It's discussed by people like Dr. Jack Kruse, David Herrera and Dr. Alexis Cowan, often in the context of modern environments that don't match our biology.

I personally use cold followed by light exposure in winter. That's part of my personal practice.

If you're curious, treat this as an experiment, not a rule.

If You Want to Go Further Down the Rabbit Hole

Jack Kruse – circadian biology and light environment | Watch here
- Jack also has a great Patreon where he shares cutting edge information on light and circadian biology. Warning… Uncle Jack is an acquired taste as far as his information delivery. He can be a tad crass, but that doesn't mean he should be ignored.
Alexis Cowan – metabolism and circadian signaling | Watch here
David Herrera episode – coming soon
Jack Kruse + Andrew Huberman + Rick Rubin talk Light | Watch here

Bryan Can Stay in the Shade. I'll Be Outside.

Not because I'm reckless. Because my body has been waiting for that light since before I was born. Yours probably has too.

The question is whether you're giving it what it expects, or just hoping supplements and willpower cover the gap.

Start with the sun. Everything else is a workaround.