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| Feeling the sun warm your body certainly feels good, but is it doing you good? For years, I assumed sunbathing was mainly about vitamin D, melanin, and mood, but recent research reveals something unexpected: certain wavelengths of sunlight actually pass through our entire bodies, boosting cellular function along the way. And it can improve your eyesight. |
| How does that work? Read on! |
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Let’s look into it,
Tim Snaith
Newsletter Editor, Healthline
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Written by Tim Snaith
August 1, 2025 • 4 min read |
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| Sunshine is doing much more than making vitamin D |
| Back in 2021, we reported on how scientists discovered that just 3 minutes of deep red light exposure once per week improved people’s color vision by 17% for up to a week. The light treatment worked by “recharging” mitochondria (think of them as your cells’ batteries), but only when given in the morning. As one scientist explained, mitochondria “are probably busy doing other things in the afternoon.”
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| Now, new research from the same University College London team takes this further. They found that invisible heat rays from the sun are able to travel completely through your body, reaching internal organs and improving cellular energy along the way.
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| When people were exposed to these rays for 15 minutes, their vision improved 24 hours later, and these improvements happened even when their eyes were wrapped in aluminum foil during exposure. This showed that the rays create whole-body effects, improving vision by enhancing mitochondria throughout the body rather than directly hitting eye cells. Wild.
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| The scientists actually photographed light coming out of people’s chests after passing through their bodies, which means we’re transparent, at least to certain types of light. The wavelengths that do it best are around 830 to 860 nanometers, aka “near infrared light.” These aren’t the rays that make vitamin D or the ones we can see, but the heat we feel in sunlight.
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| What about clothing?
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| Researchers also tested whether clothing blocks these benefits. The invisible heat rays easily passed through all six layers people wore. So you don’t even need to sunbathe to get benefits. A clothed walk outside should also deliver therapeutic rays where they’re needed.
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| Does artificial light work in the same way?
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| While energy-efficient, LED lighting only emits rays up to about 650 nanometers, which means it lacks the beneficial heat rays of natural sunlight. Traditional bulbs and firelight contained these longer wavelengths, but modern LEDs create what researchers call a “restricted spectrum.”
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| The best time of day to benefit
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| Morning sunlight, richest in beneficial rays, may be particularly valuable for this reason. Exposure to it supports healthy sleep-wake cycles, and even brief exposures to full-spectrum sunlight provide benefits we're just beginning to understand.
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