Sunlight for Testosterone and DHT: Skin, Heart, Brain and How to Sunbathe

Every living thing ran on the sun before it ran on a clock. Some butterflies literally can't fly until the sun warms them up, and the Greeks had one word, psyche, for breath, soul and butterfly. Sunlight for testosterone is the same story in hormone form. Sun on your skin tells your brain to tell your balls to make more T, your skin turns some of that T into DHT, your arteries open up, your metabolism runs cleaner and your brain makes more serotonin. Add raw fat, the stuff every hormone is built from, and that's the whole sunmaxxing protocol.

• Sun on the skin raises sex hormones through a skin-brain-gonad signal, and more sun goes with more T in people (PMID 34433056).
• Men with more daily bright light had higher T, and afternoon light mattered most (PMID 42315435).
• T peaks in late summer and bottoms out in late winter, and free T rises even more (PMID 20050857).
• Your skin makes its own T and DHT, and UVB changes how much (PMID 23435015).
• Vitamin D pills alone didn't raise T in healthy men (PMID 23686706, PMID 28938446). The light does more than the vitamin.
• UVA on the skin releases nitric oxide and lowers blood pressure (PMID 24445737).
• People who avoided the sun died earlier, mostly from heart disease (PMID 26992108).
• UV kept fat gain and insulin resistance down in mice, and vitamin D couldn't copy it (PMID 25342734).

Some butterflies can't take off until their bodies are warm enough to fly. They sit in the sun and angle their wings to bounce light onto themselves, and their whole day runs on it (PMID 28310796).

You're not that different. Your hormones, blood pressure, mood and sleep all move with the sun. The plate below is the map: five places the sun hits you, from your skin up to your body clock.

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01 / 05 · Rhythm

Your body clock. On natural light only, your body starts its night at sunset. Evening sun

Moth engraved by Moses Harris for The Aurelian, 1766, hand-tinted. Psyche meant breath, soul and butterfly. Tap a label to jump there.

Yes. UVB on your skin kicks off a signal from your skin to your brain to your balls, and your sex hormones go up. It runs through a protein in your skin cells called p53: take that out of the skin and the effect is gone. In people, more sun went with more T, and more romantic passion in both men and women (PMID 34433056).

The light itself counts, not just vitamin D. In over 2,000 men wearing light sensors for a week, the ones who got more bright light had higher T, even after accounting for vitamin D, weight, diet and exercise. Afternoon light hit hardest, and guys who were stuck indoors the rest of the time gained the most from it (PMID 42315435). Half an hour more a day lined up with roughly 10% more T.

It shows up across the year too. Men's T bottoms out in late winter and peaks in late summer, right alongside vitamin D, and their SHBG drops so more of that T is free (PMID 20050857).

Vitamin D pills are the cope version. They helped men who were deficient (PMID 21154195), but in healthy men they did nothing for T (PMID 23686706, PMID 28938446). The sun works through your skin and your body clock, not just vitamin D.

Kircher drew the sun in 1664 as a living furnace, full of fire and smoke. The real thing is weirder: a mix of different kinds of light, each one telling your body something different.

UVB is the short, burning part. It makes vitamin D in your skin (PMID 6281884) and starts the hormone signal. UVA goes a bit deeper and opens your blood vessels. Visible light hits your eyes and sets your body clock. Red and near-infrared go deepest and power up your mitochondria, the energy factories in your cells.

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01 / 05 · UVB

Makes vitamin D in your skin (PMID 6281884) and starts the skin-to-balls signal that raises T (PMID 34433056).

Athanasius Kircher's sun, from Mundus Subterraneus, 1664, hand-tinted. Tap a band to see what it does to you.

Yes, through T. Sunlight doesn't need to make DHT itself. It raises your T, and your tissues turn that T into DHT with an enzyme called 5-alpha-reductase. More T in, more DHT out.

Two things stack here. Summer sun raises your T and drops SHBG, the protein that locks T up, so more of it is free for the enzyme to convert (PMID 20050857). And your skin is one of the places that does the converting: skin cells make their own T and DHT, and UVB changes how much (PMID 23435015). The sun raises the T and your skin turns it into DHT, right there under the light.

Never block that enzyme. After puberty your bones still thicken under DHT, and your jaw and brow ridge are bone. That's your frame.

Every hormone on this list, and vitamin D too, is built from cholesterol. The sun is the signal. Fat is the material.

The same skin cells that make vitamin D from sunlight (PMID 6281884) also turn cholesterol step by step into T and DHT (PMID 23435015). Raw butter, raw cream, raw eggs, raw milk and raw meat fat bring that cholesterol in whole. Skimp on fat and the sun has nothing to build with.

Get sun on bare skin, genitals included. Your balls are where T gets made, and they're the end point of the skin-to-brain-to-balls signal (PMID 34433056). Sunning the balls is on the list at aajonus.net.

Red and near-infrared light reach them too. In mice, it rebuilt damaged testicle tissue and got sperm production going again (PMID 40351155, PMID 39450003).

But keep them cool the rest of the time. Your balls sit cooler than the rest of you for a reason: in those same mouse studies, regularly heating them was enough to shut sperm production down (PMID 40351155). Short sessions in the sun, no baking, and the loosest underwear you own, or none.

The closer you are to the equator, the stronger the UVB, so the same half hour does more.

In mice on a junk high-fat diet, regular UV kept them leaner, with better blood sugar and less fatty liver. Vitamin D pills couldn't copy it. What did copy it was raising nitric oxide in the skin, the same thing sunlight does (PMID 25342734).

Same pattern every time: people pop vitamin D expecting sun results, and it doesn't deliver, because the light does things the pill can't.

For most of history the heart was drawn as the body's sun. Turns out the sun reaches your heart through your skin.

Your skin stores nitric oxide, and UVA releases it into your blood. When researchers shone UVA on people's skin, their blood vessels opened and their blood pressure dropped, and it came straight from the store in the skin (PMID 24445737).

Over 20 years in Sweden, women who avoided the sun died at about twice the rate of the ones who got the most, mostly from heart disease (PMID 24697969). Non-smokers who avoided the sun lived about as long as smokers who sunbathed. Avoiding the sun was as bad as smoking (PMID 26992108).

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01 / 06 · Brain

Makes more serotonin on bright days, least in winter (PMID 12480364).

Tap a point to see what the sun does there.

Winter feels darker inside your head as well as outside. There's a reason.

Researchers measured serotonin coming straight out of men's brains. It was lowest in winter, and the brain made more of it the more bright sunshine there was that day (PMID 12480364).

In people with depression, less sunlight meant worse thinking and memory, and the less sun, the worse it got (PMID 19638195). Mood, sleep and focus all run on the same light signal from your eyes.

Dusk is when the light goes red and soft, and your body starts winding down for the night.

When people went camping with no electric light, their body clocks snapped back to the sun: night started at sunset and ended just after sunrise (PMID 23910656). Phone and ceiling lights at night push your clock later and wreck that.

Low evening sun is extra rich in red and near-infrared, the light that powers your mitochondria. A few minutes of deep red light sharpened people's eyesight for a whole week (PMID 34819619).

On sungazing, Aajonus kept it simple: you don't have to stare at the sun. Get the evening light on your face with your eyes open, looking near the horizon, and skip sunglasses unless your eyes are too sensitive.

In We Want To Live he said to get as much fresh air and sunshine as you can: it cuts down how long detoxing takes and makes it easier. Sunlight without sunblock or sunglasses, to heal faster.

On sunscreen he didn't hold back. In his 2012 workshop he called it very toxic. His fix for burning was fat, inside and out: people eating plenty of raw fat could sunbathe without sunblock and without burning within a few months, starting with short sessions.

He also said long sunbathing makes so much vitamin D in your skin that it can kick off a deep bone detox (The Primal Diet).

The sun is the signal and cholesterol is the material, so the food side of this is raw animal fat. Aajonus was strict and we're stricter: every animal food raw. Never cooked, never pasteurised, never frozen.

Raw unsalted butter and raw cream are the base. Add raw eggs, raw meat and fat, and organs. Warm raw milk on top; the full case for it is in raw milk for looksmaxxing. No seed oils, no salt, no supplements, no protein powder. Veg only as fresh raw juice.

Think seasons, not days. Men's T climbs from late winter to late summer as the days get longer (PMID 20050857).

Your skin catches up on the same timescale: Aajonus saw people on plenty of raw fat stop burning within a few months. Blood flow is the fastest win. Blood pressure dropped after UVA on the skin (PMID 24445737).

Aajonus's rules, plus the raw fat that makes them work.

• Eat raw fat every day: raw unsalted butter, raw cream, raw eggs, raw meat fat, and warm raw milk.
• Don't shower the morning you sunbathe. Washing strips off your skin's own oil, which is your natural sunblock.
• The night before, rub in a little unrefined cold-pressed coconut or peanut oil. Raw coconut cream on the night before works as a block. Coconut oil on its own is a tanning oil.
• Go out in the afternoon, 12 to 5. That window had the strongest link to T.
• First day of the season: 30 minutes. After that, longer each day, as The Primal Diet says.
• Don't wash the same day after, so the oil and vitamin D soak back in.
• Bare skin, no sunscreen, no sunglasses. Catch the evening sun on your face, eyes open, looking near the horizon.
• Sun the balls too, in short sessions, and wear the loosest underwear you have, or none, the rest of the day to keep them cool.
• If you burn: raw egg white, or fresh aloe gel mixed with a little royal jelly, sun-dried clay and stone-pressed olive oil, from We Want To Live.

What the sun does, and the study behind each one.