If you listen to mainstream health advice, you’d think the sun is public enemy number one. Dermatologists and health agencies have spent decades warning us about the dangers of UV exposure, lathering on SPF 50 like it’s a religious ritual, and treating the sun like a radiation death beam sent to destroy our skin.

But let’s be real for a second. Humans evolved under the sun. Our ancestors weren’t hiding in caves wearing SPF-infused loincloths. They were outside, hunting, gathering, and thriving under direct sunlight.

So why is modern society convinced that minimal sun exposure is optimal for health? Could it be that avoiding the sun might actually be contributing to a whole host of modern health issues—including low testosterone?

Let’s break down why sunlight is essential for men’s health and how getting daily exposure can supercharge your testosterone, boost your sleep quality, and maybe even justify the infamous ball-sunning trend.

Sunlight and Testosterone: The Science is Clear

Vitamin D: More Than Just a Bone Health Vitamin

The link between sunlight and testosterone starts with vitamin D. This so-called “vitamin” is actually a hormone precursor, and it plays a massive role in hormone production—including testosterone.

Studies have repeatedly shown that men with higher vitamin D levels tend to have significantly higher testosterone levels than those who are deficient.

• A 2010 study published in Hormone and Metabolic Research found that men supplementing with vitamin D (3,332 IU per day) for a year saw a significant increase in total testosterone compared to a control group.

• Another study in Clinical Endocrinology found that men with sufficient vitamin D had 25% higher testosterone than those who were deficient.

While supplementing can help, nothing beats the natural vitamin D synthesis triggered by direct sun exposure on the skin.

UV Light and Leydig Cells: How the Sun Supercharges Your T Levels

Vitamin D is just one piece of the puzzle. Sunlight—specifically UVB rays—has been shown to directly stimulate the Leydig cells in your testes, the factories responsible for cranking out testosterone.

• A 2021 study demonstrated that exposure to ultraviolet B (UVB) light enhances sex-steroid hormone levels and sexual behavior in both mice and humans, mediated by a skin-brain-gonadal axis.

• A 2014 study found that UV exposure led to significant alterations in the expression of reproductive genes and a marked increase in testosterone synthesis in human testicular cell cultures.

This is why men often report a noticeable boost in energy, libido, and overall well-being during the summer months when they get more sun exposure.

The Role of Cholesterol in Sun-Induced Testosterone Production

It’s important to note that cholesterol is a building block of testosterone. When the skin absorbs UVB light, it initiates a process that converts cholesterol into vitamin D, which in turn supports testosterone production. This is why a diet rich in healthy cholesterol sources (like grass-fed beef, egg yolks, and wild-caught fish) pairs so well with sun exposure for optimizing male hormones.

Sunlight and Sleep: The Underrated Testosterone Booster

Testosterone isn’t just about muscle gains and libido—it’s also deeply connected to sleep quality. And guess what? Sun exposure plays a major role in regulating your circadian rhythm, which in turn optimizes testosterone production.

The Morning Sunlight Effect

• Morning sunlight exposure increases serotonin, which converts into melatonin at night, helping you sleep better.

• Better sleep equals higher testosterone. One study found that getting less than 5 hours of sleep per night can decrease testosterone by up to 15%.

So if you want to boost your T levels naturally, getting outside in the morning to soak up some rays is a no-brainer.

Sunlight and Cortisol Regulation

Cortisol is the stress hormone that counteracts testosterone production. Chronic high cortisol levels (often caused by artificial light, poor sleep, and constant stress) lead to suppressed testosterone. Exposure to morning sunlight has been shown to regulate cortisol levels and support a healthier hormonal balance.

Sun on the Chest: The Forgotten Hack

You’ve probably heard of grounding, cold plunges, and red light therapy, but have you ever thought about sunning your chest? There’s something about direct sunlight on the upper body that seems to trigger a primal energy boost.

Some theories suggest that the heart and thymus gland benefit directly from UV exposure, aiding in immune function and circulation—both crucial for hormone regulation. Plus, it just feels good.

So next time you’re outside, ditch the shirt for a few minutes and let your body absorb that testosterone-boosting energy.

The Ball-Sunning Trend: Bro Science or Legit?

Yes, we’re going there. The so-called Joule’s Law of testicular sunbathing has been making waves in the biohacking and men’s health community.

The Science Behind Testicular Sunlight

• A 1939 study in Endocrinology found that UV light exposure on the chest increased testosterone by 120%, while exposure to the genitals increased it by 200%.

• More recent studies suggest that infrared and red light exposure on the testes can improve mitochondrial function and testosterone production.

While research is still limited, the anecdotal reports from men who swear by it are intriguing. Just don’t go overboard and fry the boys—moderation is key. 

If you’re skeptical about the science, try it yourself and see the difference. This ancient and powerful practice could save countless men from relying on medications and artificial treatments.