NEW STUDY: Sunlight Penetrates the Human Body, Improving Mitochondrial Function and Vision

Written by Nicolas Hulscher, MPH on July 18, 2025. Posted in Current News

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.

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