Ben Greenfield on health: what the evidence says · JRE #1069
“And so they've done these studies on testicular and sperm production. And they found that there's a wavelength. It's like 600 to 800 nanometers wavelength of light that if you expose the testicles to that for 5 to 20 minutes a day.”
What the evidence says
Photobiomodulation (red and near-infrared light) has been studied for effects on testicular tissue and sperm parameters, but almost exclusively in rodent models, and typically as a treatment to reverse damage from heat stress, toxins, or torsion rather than to boost sperm production or testosterone above normal in healthy subjects. A 2020 mouse study found that low-level laser exposure restored sperm parameters and serum testosterone that had been suppressed by induced scrotal hyperthermia, not that it raised testosterone beyond baseline in unstressed animals. No published human clinical trials establish that irradiating the testicles with 600-800 nm light for 5 to 20 minutes daily increases sperm production or testosterone in healthy men, and no specific dosing protocol matching this description has been validated in humans. Separately, a 2026 review of red light therapy marketing on social media (focused on dermatologic applications like skin and anti-aging) found that only 8.3% of promotional posts cited peer-reviewed sources at all, illustrating how loosely red light therapy claims in general circulate relative to the evidence base, though that review did not specifically examine reproductive or hormonal claims. Overall, the claim extrapolates preliminary animal research on tissue-damage recovery into a general human enhancement protocol that has not been demonstrated in controlled human studies.