What qualities make a man, a man? That’s no simple question. But from a purely biological perspective, there’s an easy answer: testosterone. Men generally produce far more testosterone than women, and it’s responsible for many of the qualities people consider “manly”—deeper voices, hairy chests, muscular frames, etc.
Man's Testosterone Problem
Unfortunately, around age 30, testosterone levels start to drop. This is normal, but that doesn’t make it easy to deal with. Waning testosterone levels can bring a lot of challenges to a man’s life—things like lower energy, reduced sexual drive & performance, a decline in muscle, as well as weight gain.  To make matters worse, testosterone is adversely affected by a host of common challenges that affect nearly all modern men, like nutrition, stress, and lack of sleep—to name just a few. These factors combine to produce dramatically decreased testosterone levels for a lot of men.
Trying to treat testosterone problems can be a double-edged sword. Doctors often suggest supplementation or medication to help with the difficulties of low testosterone or to treat testosterone abnormalities. But these conventional solutions lead to unwanted side effects for many patients. Even more challenging, some men who want to increase their testosterone levels are told by physicians that their numbers aren’t low enough to warrant treatment. As a result, dealing with low testosterone can feel like a “damned if you do, damned if you don’t” situation to a lot of men in their 30s, 40s, and 50s.
So it’s no surprise that a lot of men want a more natural option to boost their testosterone, and with it their energy, sex drive, and physical performance. One promising option is light therapy, as recent medical studies are demonstrating its immense potential for increasing male testosterone. This has been repeatedly proven in clinical trials on various mammals in the past few decades, but recent studies on human men are giving researchers and endocrinologists even more reasons for optimism.
Clinical Research Shows Light Therapy’s Potential for Increasing Testosterone
Medical scientists have been studying the effects of natural light on testosterone production for almost a century. Research over the last decade, and especially the last few years, has been even more illuminating and given the medical community more concrete reasons to believe in light therapy’s potential for increasing male testosterone.
Italian Pilot Study: A 2016 randomized, placebo-controlled pilot study conducted by the University of Siena in Italy evaluated 38 men with a diagnosed low sexual desire. Researchers measured their testosterone levels and separated the men into two groups, with one group receiving a clinical dose of light therapy in the early mornings. In addition to higher sexual satisfaction, the men in the group treated with more light saw their T-levels rise significantly. The control group did not see testosterone rises, but the active light therapy group showed a huge increase from about 2.1 ng/ml to 3.6 ng/ml in just 2 weeks. 
Dr. Andrea Fagiolini, the study’s lead researcher, explained the findings: "The increased levels of testosterone explain the greater reported sexual satisfaction. In the Northern hemisphere, the body's testosterone production naturally declines from November through April, and then rises steadily through the spring and summer with a peak in October. You see the effect of this in reproductive rates, with the month of June showing the highest rate of conception. The use of the [light therapy device] really mimics what nature does.” 
Male Fertility: Numerous other studies over the last 5 years have found that increased natural light exposure to a man’s testes and sperm actually increases sperm motility, or how well individual spermatozoa are able to move and swim. Motility is a key measure of male fertility and reproductive health. As a result, many researchers are concluding that light therapy can have a significant effect on treating male infertility. [4,5,6,7]
In addition to noting increased sperm motility, a 2017 study published in Scientific Reports found that these treatments were safe, and did not induce any oxidative DNA damage to the sperm or testes. 
To hear more about light therapy and how it can improve sex drive and performance, check out this related post. It covers encouraging research on light therapy and its positive effect on male fertility, sexual satisfaction, and performance.
Previous Laboratory Research on Mammals: Although in-human clinical research on testosterone and light therapy is still in its early stages, and more trials are needed, there’s no doubt it's very promising. For example, the recently published research on men builds on a larger base of analysis conducted on laboratory mammals and their testosterone levels.
A 2013 study in Biomedical Research found that red light therapy at 670 nanometers (nm) increased the serum testosterone levels of lab rats, with no noted side effects.  Another 2013 study on testosterone in rats published in the Nepal Medical College Journal found that the follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are connected to the production of testosterone and natural sex steroids, were elevated in rats subjected to light for 70 days.  The FSH and LH pathway is essentially the same in humans, and they’re referred to as “gonadotropins” because of their ability to stimulate testicular function
Other studies on the motility of dog and boar sperm have shown the same type of positive results in laboratory settings. [11,12]
How Does Red Light Therapy Boost Testosterone Levels?
Although numerous trials are finding increased male testosterone with light therapy, the precise reasons and biological mechanisms of action aren’t fully understood at this point. In other posts, we explained how the human body absorbs red and near infrared light, which encourages increased cellular chemical energy transportation—otherwise known as adenosine triphosphate (ATP). Just as improved function can be observed throughout various bodily processes from increased ATP energy, many of these studies suggest that red and near infrared light wavelengths can stimulate the Leydig cells, which are responsible for producing testosterone in the testicles. Its theorized that this enhanced energy production can help naturally increase testosterone hormone. [6, 9,10]
Leading researchers have posited some other theories, and they’re not mutually exclusive. Some believe that red and near infrared wavelengths stimulate photoreceptive proteins in the testes, resulting in higher testosterone production, as shown in studies as far back at 1939. 
Researchers from the aforementioned 2016 University of Siena study suggested that light therapy interacts with the pineal gland in the brain, which plays a major role in human reproduction. 
While medical science is still working on identifying the exact mechanisms, it’s pretty clear there’s a relationship between natural light and male testosterone, both in human men and other mammals. This aligns with the large amount of anecdotal evidence we hear all the time from trainers, athletes, physicians, and health & fitness pros who report major testosterone increases after using our full-body light therapy devices.
Leading Health & Fitness Pros Up Their Testosterone with Red Light Therapy
Peer-reviewed clinical research is always the most reliable indicator of whether a therapy is effective, but individual experiences are also a valuable data point, especially from leading fitness and health professionals. Many of the world’s best have tried light therapy and reported big increases in testosterone, energy, sex drive, and performance.
Ben Greenfield: The world-famous trainer & biohacker tried a few weeks of Joovv light therapy on his testicles and wrote this infamous article in Men’s Health about the big testosterone, energy, and sexual performance boost he got. Without quoting Ben directly, we’ll just say him and his wife both really noticed the effects of the Joovv.
Mike Mutzel, aka Metabolic Mike, is another top trainer who tried light therapy after working with Ben Greenfield. He was skeptical, but his energy shot up and he even posted his lab results showing his testosterone doubling after incorporating the Joovv.
UFC Champion TJ Dillashaw: He’s one of the great fighters of his era and still holds the UFC bantamweight championship. TJ penned a guest post for us a while back about how light therapy is essential to his muscle recovery routine. He also mentioned this detail about testosterone and fertility:
“Just a few years ago, I was training so hard that I ran myself into the ground. I was exerting so much effort on training (without thinking much about recovery) that my testosterone levels were shot. My wife and I were trying to get pregnant, and it wasn’t happening. Our doctor recommended red light therapy, so I looked online, found Joovv, and started working red light therapy into my nightly recovery routine at home.
Since then, I’ve been using my Joovv every night because it helps me relax physically and mentally. Not long after I started Joovvin’ at night, my T-levels improved and my wife got pregnant shortly thereafter. And 9 months later, we had a healthy baby boy! I have no doubt that red light therapy helped make that possible.”*
NFL stars like Patrick Peterson: The Arizona Cardinals star cornerback has made the Pro Bowl in all 7 of his NFL seasons. Now in his 30s, the future Hall of Famer incorporated Joovv into his offseason training and says his energy is way up.
That’s just a small sampling of many elite competitors who have seen major boosts in testosterone, sex drive, and general energy from light therapy and Joovv.
An Important Note on Heat & Safety
No man wants to put their sexual health in jeopardy with a risky or unproven treatment. But some men have reported potentially negative effects to their testes when using some forms of energy therapy in the past. However, the key is that those negative effects have come from suboptimal products with excessively long wavelengths of light that produce too much heat.
The Joovv devices incorporate clinically-proven red and near infrared wavelengths in the mid-600s & mid-800s nm range, also known as the “therapeutic window” of light therapy. Because wavelengths above 1,000 nm produce much more radiant heat, it’s critical to use a high-quality LED light therapy device that delivers optimal power with proven (and safe) wavelengths. All of Joovv’s devices were specially designed to meet these vital criteria.
Although not specifically cleared for testosterone treatments, Joovv’s products are registered as class II medical devices by FDA and their entire production process has passed rigorous quality and safety inspections. Beyond regulatory bodies, light therapy with red and near infrared wavelengths has been deemed as very low-risk by scientists too. A 2013 study of light therapy treatments conducted by Harvard and MIT researchers praised its “noninvasive nature and almost complete absence of side effects.” 
Conclusion: Light Therapy Could be a Game-Changer for Boosting Natural Male Testosterone
Emerging research on light therapy and its effect on male testosterone, fertility, and sex drive is extremely encouraging. Taken together with previous lab research, and the current experiences of top athletes and trainers using Joovv, it’s clear that light therapy has the potential to be a game-changer for men who are looking for an increase in natural testosterone production.
Scientific Sources and Medical References:
 Healthline, Gotter A and Rogers G, MD. Low Testosterone in Men. Healthline. Jul 2016.
 Fagiolini A et al. Lack of interest in sex successfully treated by exposure to bright light. European College of Neuropsychopharmacology. Sept 2016.
 European College of Neuropsychopharmacology (ECNP). "Lack of interest in sex successfully treated by exposure to bright light." ScienceDaily. ScienceDaily, 18 September 2016.
 Vladimirovich Moskvin S., Ivanovich Apolikhin O. Effectiveness of low level laser therapy for treating male infertility. Biomedicine (Taipei). 2018 June; 8(2):7.
 Ban Frangez H., Frangez I., Verdenik I., Jansa V., Virant Klun I. Photobiomodulation with light-emitting diodes improves sperm motility in men with asthenozoospermia. Laser in Medical Science, 2015 Jan;30(1):235-40.
 Salman Yazdi, R., Bakhshi, S., Jannat Alipoor, F. et al. Effect of 830-nm diode laser irradiation on human sperm motility. Lasers Med Sci. (2014) 29: 97.
 Chow KW, Preece D, Burns MW. Effect of red light on optically trapped spermatozoa. Biomedical Optics Express. (2017) Aug 23;8(9):4200-4205.
 Preece D., Chow KW, Gomez-Godinez V., Gustafson K., et al. Red light improves spermatozoa motility and does not induce oxidative DNA damage. Scientific Reports. 2017 Apr 20;7:46480.
 Ahn JC, Kim YH and Rhee CK. The effects of low level laser therapy (LLLT) on the testis in elevating serum testosterone level in rats. Biomedical Research. 2013; 24(1):28-32.
 Biswas NM, Biswas R, et al. Effect of continuous light on spermatogenesis and testicular steroidogenesis in rats: Possible involvement of alpha 2u-globulin. Nepal Med Coll J. 2013;15(1):62-64.
 Yeste M., Codony F., Estrada E., Lleonart M., et al. Specific LED-based red light photo-stimulation procedures improve overall sperm function and reproductive performance of boar ejaculates. Scientific Reports. 2016 Mar 2;6:22569.
 Corral-Baqués M., Rigau T., Rivera M., Rodríguez JE, Rigau J. Effect of 655-nm diode laser on dog sperm motility. Lasers in Med Science. 2005;20(1):28-34.
 Myerson, A. Influence of ultraviolet radiation on excretion of sex hormones in the male. Endocrinology. 1939;25:7-12.
 Aliendri V., Spina V., Morini A. The Pineal Gland and Reproduction. Human Reproduction Update.1996 May-Jun;2(3):225-35.
 Avci P, Gupta A, et al. “Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring.” Seminars in Cutaneous Medicine and Surgery. Mar 2013; 32(1): 41-52.