Supporting healthy testosterone naturally comes down to the basics, sleep, resistance training, and managed stress, plus one lever most men overlook: keeping the testicles cool, since heat impairs the temperature-sensitive Leydig cells that produce most of a man's testosterone.
How Heat Affects Leydig Cells
Leydig cells, responsible for producing roughly 95 percent of a man's testosterone, rely on temperature-sensitive enzymes to convert cholesterol into testosterone. [1] When scrotal temperature rises, these enzymes show reduced activity, leading to a buildup of raw materials inside the cells and increased markers of cellular stress and cell death. [1] This effect has been observed directly in cellular and animal research, making it a demonstrated cellular mechanism, not a hypothesis.
Why the Testicles Need to Stay Cool
The testicles sit outside the body because they are designed to operate several degrees Fahrenheit below core body temperature. This cooler environment is crucial for the optimal function of Leydig cells and sperm production. [3] When heat exposure closes this temperature gap, the biology suffers, impairing testosterone production and sperm development.
Real-World Heat Sources
Activities like sauna use, prolonged sitting, or wearing tight synthetic underwear can raise scrotal temperature enough to disrupt Leydig cell function. [4] While sauna use provides proven health benefits, it also raises scrotal temperature, which can temporarily impair testosterone production. Managing scrotal temperature during heat exposure is key to keeping the testicles cooler while the rest of the body takes the heat.
The Practical Takeaway
Whole-body heat is good for men, and the testicles are a part that does better staying cool while the rest of the body takes the heat. The fix is mechanical, not behavioral. Give them airflow, keep moisture moving, and bring the temperature down directly during the session. Whether that cellular effect translates to lower circulating testosterone in healthy men over years hasn't been settled by large human trials, but the mechanism itself is not in dispute.
Where Oakman Fits
Oakman is built to solve exactly this problem, starting with the part no ordinary underwear has: a removable cold pack in a medical-grade nylon shell that sits in a front pocket and rests against the scrotum through a layer of soft fabric during a sauna session, cooling the testicles right where heat rises fastest while the rest of the body takes the heat. The brief around it keeps the area cool the rest of the day too. The fabric is Siro-spun TENCEL-branded MicroModal, a soft, breathable natural fiber made from wood pulp that moves moisture better than polyester, which is less breathable and can feel clammy while shedding microplastics, or cotton, which holds sweat; as a natural fiber, TENCEL-branded MicroModal doesn't shed microplastics the way synthetics do. An athletic gusset gives the testicles room and airflow instead of pressing them tightly against the body. Fabric, fit, and active cooling work together to keep the testicles closer to the temperature range they are designed for.
Join the Founding 100
Oakman is sauna cooling for men, launching early fall 2026. Founding members get first access and founding pricing locked in. Reserve your spot.
Frequently asked questions
Does underwear type affect scrotal temperature?
Tight or synthetic underwear can trap heat and raise scrotal temperature; breathable, airflow-friendly options help keep it cooler.
How does sauna use affect testosterone?
Sauna use raises scrotal temperature, which can temporarily impair Leydig cell function and testosterone production. Active cooling during sauna sessions can help mitigate this effect.
What is the best fabric for keeping the testicles cool?
Natural fibers like TENCEL-branded MicroModal are breathable and trap less heat compared to synthetic materials.
Can lifestyle changes support healthy testosterone levels?
Maintaining a healthy weight, regular exercise, and managing scrotal temperature can all support optimal testosterone production.
This guide is educational and not medical advice. Heat's effect on testicular cell function and sperm is shown in cellular and animal research; whether it shifts a healthy man's testosterone levels long-term is not established. These statements have not been evaluated by the FDA. Oakman is not intended to diagnose, treat, cure, or prevent any disease or condition, including infertility or changes in testosterone, and makes no claim to increase testosterone or improve fertility or sperm quality. Individual results vary. Consult a qualified healthcare professional before changing your health routine.
References
- Cai H, Qin D, Peng S. (2021). Responses and coping methods of different testicular cell types to heat stress: overview and perspectives. Bioscience Reports. [Link]
- Durairajanayagam D, Agarwal A, Ong C. (2015). Causes, effects and molecular mechanisms of testicular heat stress. Reproductive BioMedicine Online. [Link]
- Garolla A, et al.. (2013). Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Human Reproduction. [Link]
