In a recent Instagram post, Huberman, a neuroscientist and professor at Stanford University’s School of Medicine Department of Neurobiology, highlighted ways sunlight exposure can boost your health—and your T levels.
“Sunlight on skin (mid-late day) = increased testosterone & estrogen. Don’t burn!” Huberman posted.
Hone Health Chief Medical Officer Jack Jeng, M.D., says Huberman is on to something. “Exposure to ultraviolet light from the sun has been shown to increase sex steroid levels in men, including total testosterone,” says Jeng, M.D. This may even help explain why men’s T levels peak in the summer and drop in the winter, he says.
Sun Exposure and Testosterone
Huberman previously discussed light’s potential to increase testosterone in an April 2022 podcast episode titled “Using Light (Sunlight, Blue Light and Red Light) To Optimize Health.”
In the episode, Huberman cited a 2021 study exploring the effects of ultraviolet B (UVB) exposure—light from sunshine—on hormones. Over a month, men who got 20 to 30 minutes of sun exposure 2 to 3 times a week doing normal outdoor activities (gardening, reading, walking, etc.) had notably higher levels of testosterone.
In an 2021 Instagram post about the study, Huberman wrote, “It appears the skin is acting as a hormone-promoting organ to exert these effects. [The] p53 [gene] in keratinocyte skin cells can activate the pituitary gland and hypothalamus if the skin is exposed to ample sunlight (UV-B light in particular…). That in turn, causes increases in LH/FSH that trigger testosterone, estradiol and progesterone.”
In other words: When your skin is exposed to the sun, skin cells called keratinocytes (common skin cells) trigger the pituitary gland. The pituitary gland releases follicle stimulating hormone (FHS) and luteinizing hormone (LH), the latter of which stimulates testosterone production in the testes.
Other Links Between Sunlight and Testosterone
Research has also established other links between sunlight and testosterone. Sunlight can increase vitamin D levels–and having more vitamin D may increase testosterone.
The American Urological Association found a significant link between vitamin D and testosterone in 2015. Scientists suspect that when you liver processes vitamin D from the sun or food, it sends a signal to the testes to convert total testosterone into free testosterone, the unbound testosterone your body can use.
But Jeng warns that soaking up the sun doesn’t come without risks. “Too much ultraviolet radiation can damage the DNA in our skin cells, leading to wrinkles and even skin cancer,” he says.
Fortunately, taking vitamin D supplements can similarly boost vitamin D levels—and testosterone—without the risk of getting burned. “One study conducted in healthy overweight men with baseline vitamin D deficiency and low testosterone levels demonstrated that daily vitamin D supplementation for 1 year significantly increased vitamin D levels and boosted total testosterone by 25 percent.”