Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision.

Long wavelength red light that can extend beyond the human visual range penetrates deeply through biological tissue. Exposure to these longer wavelengths improves mitochondrial function and ATP production. This can translate to improved physiological performance, particularly in the CNS, including the visual system. Light driven metabolic improvements to regional exposure can impact systemically. Here we show that infrared wavelengths from sunlight can be measured after they pass through the human thorax. We then select a prominent transmitted solar wavelength range (830-860 nm) and deliver this to the thorax of subjects in the lab in controlled 15 min exposures with and without ocular involvement. Clothing reduced wavelength intensity but was not a barrier. These exposures were associated with significantly improved visual function when measured 24 h later even in subjects in which light was blocked from the eyes. Our data show that longer wavelengths of sunlight penetrate through the human body and, consistent with animal studies, have the ability to improve function. While infrared light has been used on targeted tissues, its ability to improve distal tissues in humans has not been explored. This study also highlights the potentially important therapeutic value of sunlight whose longer wavelengths can reach key organs even through clothing and likely promote mitochondrial function counteracting the decline with age and disease.