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Dr. Andrew Huberman: How UVB to skin raises testosterone

Through melanopsin retinal cells, UVB drives key hormonal cascades. Testosterone rises, melatonin falls at night, and pain tolerance shifts via endorphins.

Andrew Hubermanhost
Feb 25, 202638mWatch on YouTube ↗

At a glance

WHAT IT’S REALLY ABOUT

How sunlight and red light shape hormones, mood, immunity, healing

  1. Light is electromagnetic energy that different tissues absorb at different wavelengths, allowing it to alter neural activity, hormones, and even gene expression across the body.
  2. Short-wavelength light (especially UVB/blue) strongly suppresses melatonin via retinal melanopsin cells, helping set daily and seasonal biological timing, while also affecting mood and pain through brain circuits.
  3. UVB exposure to skin (and in some cases eyes) is linked to changes in sex hormones, fertility markers, pain tolerance, immune readiness, and tissue turnover (skin/hair/nails), with special considerations in winter and for SAD.
  4. Long-wavelength red/near-infrared light can penetrate deeper into tissue, support mitochondrial function, and may improve acne/scars and even age-related declines in visual function; timing, distance, and safety are emphasized.

IDEAS WORTH REMEMBERING

5 ideas

Treat light as a biological input, not just illumination.

Huberman frames light as capable of driving electrical signals, hormonal cascades, and gene-expression changes, which is why timing, intensity, and wavelength matter for health outcomes.

Melanopsin retinal cells are central to light’s systemic effects.

These intrinsically photosensitive ganglion cells respond strongly to short-wavelength light and relay signals that shut down melatonin and influence downstream brain/body systems.

Avoid bright/blue-leaning light at night to protect melatonin signaling.

Bright overhead light at night can rapidly drop melatonin; repeated nighttime suppression disrupts the nightly timing signal that supports sleep and broader physiology.

Seasonal changes in melatonin are normal; match light exposure to season when possible.

Longer melatonin duration in winter is expected; spending more time outdoors in spring/summer and relatively more indoors in winter can be healthy unless mood symptoms (e.g., SAD) indicate a need for added winter light.

UVB to skin is linked to increases in testosterone/estrogen and mating-related behavior.

Cited data (including mouse mechanisms and human measures) suggest sufficient UVB skin exposure can increase sex hormones while maintaining appropriate ratios, with associated changes in sexual motivation and some fertility-related markers.

WORDS WORTH SAVING

5 quotes

Light is electromagnetic energy.

— Andrew Huberman

Melatonin is a transducer. It's a communicator of how much light, on average, is in your physical environment.

— Andrew Huberman

If you wake up in the middle of the night... your melatonin levels... will immediately plummet to near zero or zero.

— Andrew Huberman

Avoid exposure to UVB light from artificial sources between the hours of 10:00 pm and 4:00 am.

— Andrew Huberman

Red light: a novel non-pharmacological intervention to promote alertness in shift workers.

— Andrew Huberman

Light physics: wavelengths and tissue penetrationRetina photoreceptors: rods, cones, melanopsin ganglion cellsMelatonin as seasonal and nightly signalNight light exposure and circadian disruptionUVB: skin-brain-gonad axis, sex hormones, fertilityUVB: pain tolerance, endorphins, periaqueductal grayRed/near-infrared light: mitochondria, ROS, vision protocols, shift work

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