For years, we've been cautioned to fear the sun, warned about its potential to harm our skin and eyes. Yet, as A Midwestern Doctor and emerging research suggest, this narrative may not tell the full story. A ground-breaking study published in Scientific Reports (abstract below), reveals that sunlight, particularly its infrared wavelengths, may offer significant health benefits for our eyes and overall well-being, challenging the conventional wisdom that sunlight is primarily a danger to avoid.
The study demonstrates that longer wavelengths of sunlight, specifically in the near-infrared range (830–860 nm), can penetrate deeply through the human body, even through clothing. In a trial involving 40 adults, just 15 minutes of exposure to 850 nm near-infrared (NIR) light directed at the back led to measurable improvements in vision 24 hours later. Remarkably, these benefits occurred even when participants' eyes were completely covered with foil, proving that the effect is systemic rather than dependent on light entering the eyes directly.
Key findings include a 16% improvement in tritan (blue-yellow) colour contrast sensitivity and a 9% improvement in protan (red-green) sensitivity. Even in participants with blocked ocular exposure, tritan sensitivity improved by 7%. These results suggest that infrared light interacts with the body's tissues, likely enhancing mitochondrial function and ATP production, which in turn supports the central nervous system, including the visual system.
Mitochondria, the powerhouses of our cells, rely on light, particularly infrared wavelengths, to optimise energy production. The study highlights that these wavelengths penetrate the torso, reaching internal tissues and boosting mitochondrial activity. This systemic effect can enhance cellular health far beyond the site of exposure, improving sensory functions like vision. Unlike artificial lighting, which often lacks infrared and emits harmful blue light (400–450 nm) that increases oxidative stress, natural sunlight provides a balanced spectrum that supports cellular repair and resilience.
A surprising revelation from the study is that clothing does not significantly impede infrared light. Even six layers of common garments, such as T-shirts and sweaters, were nearly 100 times more transparent to 850 nm light than to visible light. This means that even fully clothed, brief daily exposure to sunlight can deliver therapeutic benefits to your tissues, making it a practical and accessible health tool.
A Midwestern Doctor has long argued that our fear of the sun oversimplifies its role in human health. While excessive ultraviolet (UV) exposure can indeed cause harm, the broader spectrum of sunlight, particularly its infrared components, appears to be a vital biological signal that modern lifestyles often lack. Most indoor LED lighting omits these beneficial wavelengths, potentially contributing to mitochondrial dysfunction and sensory decline over time. As the study warns, our reliance on artificial light may be depriving us of essential health benefits.
The findings suggest that just 15 minutes of daily sunlight exposure, even through clothing, could support eye health by enhancing mitochondrial function. This is particularly relevant in an age where screen time and indoor living dominate, exposing our eyes to excessive blue light and minimal natural wavelengths. Incorporating short periods of outdoor time, even during a walk or while sitting by a window, could be a simple yet powerful way to maintain visual acuity and overall cellular health.
In conclusion, the narrative that sunlight is something to fear is incomplete. As this study and voices like a Midwestern Doctor emphasise, full-spectrum sunlight, particularly its infrared components, offers profound benefits for mitochondrial function and vision. By embracing safe, moderate exposure to natural light, we can harness its therapeutic potential to support our eyes and overall health.
https://www.thefocalpoints.com/p/new-study-sunlight-penetrates-the
"NEW STUDY: Sunlight Penetrates the Human Body, Improving Mitochondrial Function and Vision
Just 15 minutes of fully clothed infrared sunlight exposure triggered systemic effects and measurable improvements in vision — even with eyes completely covered.
A new study published in Scientific Reports titled, Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision, confirms what animal studies have long suggested: longer wavelengths of sunlight—particularly in the infrared range (830–860 nm)—can penetrate the human body and improve mitochondrial function systemically. Remarkably, even 15 minutes of back exposure (fully clothed) improved vision 24 hours later — without any light entering the eyes.
40 adults (ages 25–63) participated in the study. Researchers first measured sunlight transmission by placing a radiometer against the chest of shirtless participants standing in direct midday sunlight. In a controlled lab setting, subjects were then exposed to 15 minutes of 850 nm near-infrared (NIR) LED light directed at their backs. Visual performance was evaluated before and 24 hours after exposure using color contrast sensitivity tests. To isolate systemic effects from direct eye exposure, a subgroup wore foil-wrapped head coverings to fully block light from reaching the eyes.
Key Findings
Sunlight penetrates the human torso. Infrared wavelengths (especially 850 nm) passed through the chest and back, reaching internal tissues. Peak transmission was observed between 800–875 nm.
Mitochondrial boost to visual function. A single 15-minute exposure to 850 nm light led to a 16% improvement in tritan (blue-yellow) contrast sensitivity and a 9% improvement in protan (red-green) sensitivity 24 hours later — even in dim lighting conditions.
Systemic effect confirmed. In participants whose heads were completely covered with foil (blocking all ocular exposure), tritan sensitivity still improved by 7%, proving that long-wavelength light acts systemically — likely via mitochondrial and cytokine signaling pathways.
Clothing is not a barrier. Even six layers of common garments (T-shirt, shirt, wool sweater) were nearly 100 times more transparent to 850 nm light than to visible light, allowing infrared to reach the skin and tissues underneath.
Built environment warning. Most indoor LED lighting lacks infrared and instead emits sharp peaks in the blue spectrum (400–450 nm), which are known to impair mitochondrial function and elevate oxidative stress, especially in the absence of balancing long wavelengths.
These findings underscore the critical role of full-spectrum sunlight — particularly its infrared components — in maintaining cellular health and sensory function. As modern environments increasingly rely on artificial lighting that omits these beneficial wavelengths, we are depriving our bodies of essential biological signals. Daily exposure to natural sunlight, even through clothing, appears to be a simple yet powerful tool to support mitochondrial health and optimize vision.
https://www.nature.com/articles/s41598-025-09785-3
Abstract
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."