Welcome back to Protocols Study Group — my YouTube-exclusive series where I'm working through Andrew Huberman's book Protocols: An Operating Manual for the Human Body, one protocol at a time. This is essentially my version of fan art. I'm not affiliated with Huberman, his podcast, or Stanford — I'm simply a fan, reading the book, highlighting what sticks, and teaching it back to you because that's how it solidifies in my brain.
Last episode we covered Sleep Protocol 1: view sunlight as soon as possible after waking. Quick recap: morning light tells your brain's master clock — the suprachiasmatic nucleus, or SCN — what time it is. It suppresses leftover melatonin, suppresses adenosine, and raises cortisol, which promotes wakefulness. Simply put: we win by sleeping.
This episode is Sleep Protocol 2: get sunlight in the late afternoon.
The protocol: 10–15 minutes before sunset
Go outside 10–15 minutes before sunset if you can. Face or walk west, toward the sun. That's it. The second bookend to your day.
Your brain has two clocks, singing in a round
Here's the part that blew my mind. The SCN has two oscillators — two roughly 24-hour rhythms of electrical activity, offset from one another. Huberman describes them as singing in a round, with peaks happening at different yet specific moments in the 24-hour cycle. One entrains to sunrise, the other to sunset, and they communicate so neither runs too fast or too slow. Together they generate the coherent daily rhythm that all your other cells follow — and they let your clock shift as days get longer and shorter across the seasons.
Morning sun sets the morning oscillator. Afternoon sun sets the evening one. You need both bookends.
Afternoon light protects your night
This is the payoff. Afternoon sunlight reduces the sensitivity of the neural circuits in your retinas — so the artificial light you see after dark doesn't hit as hard. Your phone, your light bulbs: they disrupt melatonin and the other circadian molecules much less when you've had afternoon sun. Think of it as a shield against evening light.
So the full-day cycle looks like this: morning sun tells the brain to be awake — regulate the hormones, the adenosine, the cortisol. Afternoon sun tells the brain the day is done — start winding down for bed.
Why this matters more than ever
Humans spent tens of thousands of years as hunter-gatherers, then farmers — outdoors, in sunlight. Our bodies evolved to be regulated by the sun. Only in the last 50–100 years have we moved inside: candlelight, then incandescent bulbs, then LEDs, then screens. All this fake light — and is it any wonder depression, health issues, and weight gain are rising? It's all tied to poor sleep and not seeing the sun.
My reality check
Now, my reality: I live in Northwest Washington. I wake up at 5 or 6 in the morning, the sun isn't up until 7:30, and it's down by 7 PM. Dinner, kids — getting outside twice a day is genuinely hard. But now that I understand why, I try harder. I stand in the driveway where the trees don't block the light. And just that little bit has started to improve my sleep — I fall asleep quicker and feel more energized when I wake up.
Huberman says even having caffeine or a light breakfast in the morning is fine. The sun is what sets you up for a good day.
What about a light box?
The book mentions supplemental systems like a 10,000 lux light. They help, but even that doesn't deliver the sun's full range of short and long wavelengths. Huberman uses one himself — and still goes outside as soon as he can. You want that cortisol peak as soon as possible after waking so it can bottom out at the right time of day. The real sun is still the gold standard.
The road ahead
There are 15 protocols in the sleep section alone — then exercise, stress control, nutrition, and personal growth. We're going through all 15 sleep protocols before moving on. Leave a comment, join the study group, and share this with someone who'd enjoy it.
Show notes
- Book: Protocols: An Operating Manual for the Human Body by Andrew Huberman
- Protocol: Sleep Protocol 2 — sunlight in the late afternoon, 10–15 minutes before sunset, facing or walking west
- Key idea: the SCN's two oscillators (morning/evening) sing in a round; afternoon sun sets the evening clock and shields the night from artificial light
- Kevin's takeaway: morning sun + afternoon sun = the two bookends of a healthy day
- Disclaimer: independent fan-made educational project. Not affiliated with, endorsed by, or sponsored by Andrew Huberman, Huberman Lab, or Stanford University. For educational purposes only — not a substitute for professional medical advice.