Most organs and glands of the body are covered by several inches of either bone, muscle, fat, skin or other tissues, making direct light exposure impractical, if not impossible. However, one of the notable exceptions is the male testes.

Is it advisable to shine red light directly on one’s testicles?

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Research is highlighting several interesting benefits to testicular red light exposure:

Fertility Boosted?

Sperm quality is the primary measure of fertility in men, as the viability of spermatozoa is generally the limiting factor to successful reproduction (from the male’s side).

Healthy spermatogenesis, or the creation of sperm cells, happens in the testicles, not so far from the production of androgens in the Leydig cells. The two are highly correlated in fact – meaning that high testosterone levels = high sperm quality and vice versa. It’s rare to find a low testosterone man with great sperm quality.

Sperm are produced in the seminiferous tubules of the testes, in a multi-step process involving several cell divisions and maturation of these cells. Various studies have established a very linear relationship between ATP/energy production and spermatogenesis:

Drugs and compounds which interfere with mitochondrial energy metabolism in general (i.e. Viagra, ssris, statins, alcohol, etc.) have an extremely negative effect on sperm production.

Drugs/compounds which support ATP production in mitochondria (thyroid hormones, caffeine, magnesium, etc.) boost sperm counts and general fertility.

More so than other bodily processes, sperm production is highly dependent on ATP production. Given that red & infrared light both enhance ATP production in mitochondria, according to the leading research in the field, it should come as no surprise that red/infrared wavelengths have been shown to boost testicular sperm production and viability of the sperm in various animal studies. Conversely, blue light, which harms the mitochondria (suppressing ATP production) reduces sperm count/fertility.

This applies not only to the sperm production in the testicles, but also directly to the health of free sperm cells post-ejaculation. For example studies have been done on in vitro fertilization (IVF), showing superior outcomes under red light in both mammals and fish sperm. The effect is especially profound when it comes to sperm motility, or ability to ‘swim’, as the tail of sperm cells are powered by a row of red light sensitive mitochondria.

Summary

In theory, red light therapy properly applied to the testicle area shortly before sexual intercourse could produce a greater chance of successful fertilization. Furthermore, consistent red light therapy over the days prior to sexual intercourse might further increase chances, not to mention reduce chances of abnormal sperm production.

Testosterone Levels Potentially Tripled?

It has been known scientifically since the 1930s that light in general can help males to produce more of the androgen testosterone. Initial studies back then examined how isolated light sources on the skin and body affect hormone levels, showing a significant improvement by using incandescent bulbs and artificial sunlight.

Some light, it seems, is good for our hormones. Conversion of skin cholesterol into vitamin D3 sulfate is a direct link. Though perhaps more importantly, the improvement in oxidative metabolism and ATP production from red/infrared wavelengths has broad reaching, and often underestimated, effects on the body. After all, cellular energy production is the basis of all functions of life.

More recently, studies have been done on direct sunlight exposure, firstly to the torso, which reliably increases male’s testosterone levels by anywhere from 25% to 160% depending on the person. Sunlight exposure directly to the testes though has an even more profound effect, boosting testosterone production in Leydig cells by an average of 200% – a large increase over baseline levels.

Studies linking light, particularly red light, to the testicular function of animals have been performed for almost 100 years now. Initial experiments focused on male birds and small mammals such as mice, showing effects such as sexual activation and recrudescence. Testicular stimulation by red light has been researched for almost a century, with studies linking it to healthy testicular growth and superior reproductive outcomes in almost all cases. More recent human studies support the same theory, showing potentially even more positive results compared to birds/mice.

Does red light on testes really have dramatic effects on testosterone?

Testicular function, as mentioned above, is dependent on energy production. While this can be said about practically any tissue in the body, there is evidence that it is especially true for the testes.

Explained in greater detail on our red light therapy page, the mechanism via which red wavelengths work is supposedly to stimulate ATP production (which can be thought of as cellular energy currency) in our mitochondria’s respiratory chain (look into cytochrome oxidase – a photoreceptive enzyme – for more info), increasing the energy available to the cell – this applies to Leydig cells (testosterone producing cells) just as much. Energy production and cellular function are commensurate, meaning more energy = more testosterone production.

More so than that, whole body energy production, as correlated with / measured by active thyroid hormone levels, is known to stimulate steroidogenesis (or testosterone production) directly in the Leydig cells.

Another potential mechanism involves a seperate class of photoreceptive proteins, known as ‘opsin proteins’. The human testes are especially abundant with various of these highly specific photoreceptors including OPN3, which are ‘activated’, much like cytochrome, specifically by wavelengths of light. Stimulation of these testicular proteins by red light induces cellular responses that may ultimately lead to increased testosterone production, amongst other things, although research is still in the preliminary stages regarding these proteins and metabolic pathways. These type of photoreceptive proteins are also found in the eyes and also, interestingly, the brain.

Summary

Some researchers speculate that red light therapy directly on the testicles for short, regular periods would raise testosterone levels over time. Downstream this might potentially lead to a holistic effect on the body, raising focus, improving mood, increasing muscle mass, bone strength and lowering excess body fat.

Type of light exposure is crucial

Red light can come from a variety of sources; it is contained in the wider spectra of sunlight, most home/work lights, street lights and so on. The problem with these light sources is that they also contain contradictory wavelengths such as UV (in the case of sunlight) and blue (in the case of most home/street lights). Additionally, the testicles are especially sensitive to heat, more so than other parts of the body. There’s no point applying beneficial light if you are simultaneously cancelling the effects with harmful light or excess heat.



Blue & UV light’s effects

Metabolically, blue light can be thought of as the opposite of red light. While red light potentially improves cellular energy production, blue light worsens it. Blue light specifically damages cell DNA and the cytochrome enzyme in mitochondria, preventing ATP and carbon dioxide production. This can be positive in certain situations such as acne (where the problematic bacteria are killed), but over time in humans this leads to an inefficient metabolic state similar to diabetes.

Red Light vs. Sunlight on testicles

Sunlight has definite beneficial effects – vitamin D production, improved mood, increased energy metabolism (in small doses) and so on, but it is not without its downsides. Too much exposure and you not only lose all benefits, but create inflammation and damage in the form of sunburn, eventually contributing the skin cancer. Sensitive areas of the body with thin skin are especially prone to this damage and inflammation from sunlight – no area of the body more so than the testes. Isolated sources of red light such as LEDs are well studied, seemingly with none of the harmful blue & UV wavelengths and so no risk of sunburn, cancer or testicular inflammation.

Don’t heat the testicles

Male testicles hang outside of the torso for a specific reason – they operate most efficiently at 35°C (95°F), which is a full two degrees below normal body temperature of 37°C (98.6°F). Many types of lamps and bulbs used by some for light therapy (such as incandescents, heat lamps, infrared lamps at 1000nm+) give off a significant amount of heat and therefore are NOT suitable for use on the testicles. Heating the testicles while attempting to apply light would give negative results. The only ‘cold’/efficient sources of red light are LEDs.

Bottom Line

Red or infrared light from an LED source (600-950nm) has been studied for use on the male gonads Some of the potential benefits are detailed above

Sunlight can also be used on the testes but only for short periods and it is not without risks.

Avoid exposure to blue/UV.

Avoid any sort of heat lamp/incandescent bulb.

The most studied form of red light therapy is from LEDs and lasers. Visible red (600-700nm) LEDs seem to be optimal.

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