Nicholas Witton, a researcher in non-visible spectrums of light and sleep medicine, joined Sunlight Matters to unpack a revolutionary idea: that light, particularly natural daylight and near-infrared light, is not just a passive background element but a vital input to human health. Like food or air, light is a resource our bodies actively use. In fact, we might even consider it a form of nutrition.

The Decline of Natural Light

Humans evolved outdoors, exposed to the full spectrum of sunlight. Just a century ago, most people still spent most of their time outside. Today, we spend more than 90 per cent of our time indoors, under artificial light, much of which is narrow-spectrum, blue-heavy LED lighting. These lights may be energy-efficient, but they exclude important parts of the light spectrum, especially near-infrared.

Nicholas draws a stark comparison: for the first time in human history, we are living under a restricted light diet. As the physicist Robert A E Fosbury has suggested, our bodies are like antennae, which are designed to receive and respond to the full electromagnetic spectrum.

Remove that input and, much like a plant moved from a sunny windowsill to a cupboard, our health starts to wilt.

What Is Near-Infrared Light and Why Does It Matter?

While most research has focused on the visible light spectrum, the colours of the rainbow, over 50 per cent of sunlight is actually near-infrared, which is invisible to the naked eye. This wavelength penetrates deep into the body, even through clothing, and interacts with our cells in surprising ways.

One of the key findings in emerging research, including work by UCL’s Glen Jeffery, shows that near-infrared light can influence our mitochondria, the energy powerhouses of our cells, and may directly affect glucose metabolism and ATP production. In one experiment, shining near-infrared light on the body resulted in an immediate decrease in glucose levels, suggesting a potentially powerful tool in the fight against diabetes and other metabolic diseases.

Fitness Redefined: Fit for Your Environment

Fitness, Nicholas argues, shouldn’t just be about lifting weights or running marathons. True fitness is about being well adapted to your environment, and for humans, that environment includes the sun. Someone living under the wrong light conditions is like a tomato plant growing in a cupboard. You won’t get tomatoes, just a lot of wilt.

This redefinition encourages a subtle but profound shift. Instead of obsessing over calories, step counts, and gym routines alone, we should consider how much time we spend outside and under what kind of light.

The fundamental elements that produce life and therefore health and well-being are all facilitated by the mechanics of light, from which nutrition, exercise and sleep all help facilitate these processes.

A modern-day scurvy

Modern architecture and lighting design often unintentionally block or filter out the most beneficial parts of the solar spectrum. Glass is frequently coated to reduce heat, which also means it blocks near-infrared light. Even our choice of light bulbs has changed. The old incandescent bulbs, long criticised for inefficiency, actually provided a broad spectrum of light, including healthy red and near-infrared wavelengths. LED bulbs, by contrast, produce a much narrower light spectrum.

Nicholas recounts how one of his colleagues at UCL, Bob Fosbury, described this growing deficiency as “a modern-day scurvy”, as we start to suffer the effects of infrared starvation.

Scurvy was a condition caused not by infection or trauma, but by an invisible deficiency - vitamin C.

Just as sailors once fell ill from a lack of that one vitamin before science caught up, so too might modern humans be suffering from a slow, cumulative deprivation of near-infrared light. It is a problem hidden in plain sight.

New Findings on LED Lighting and Visual Performance

A recent study led by Glen Jeffrey at UCL , titled "LED lighting undermines visual performance," directly supports these concerns. It highlights that typical LED lighting (approximately 350–650 nm) lacks deep red and infrared wavelengths (670–900 nm), which are crucial for healthy mitochondrial function. Instead, LEDs tend to emphasise blue light (420–450 nm), which can suppress mitochondrial respiration.

In a striking experiment, participants who worked exclusively under blue-dominant LED lighting experienced improved colour perception across blue-yellow and red axes once supplemented with a fuller sunlight spectrum for just two weeks. This demonstrates that LED lighting can impair normal colour vision. As the retina is especially dense in mitochondria and highly metabolically active, this could accelerate aging or visual decline.

Crucially, mitochondria respond to light exposure regionally but communicate systemically, influencing serum cytokine patterns and potentially impacting metabolism and inflammation across the body. The paper suggests that simply restoring more natural spectral balance to indoor lighting could be a highly cost-effective public health intervention, especially for elderly populations or clinical environments.

What Can We Do Now?

While the research continues, there are simple steps people can take immediately:

• Spend time outdoors, especially in the morning

• Walk part of your commute

• Consider replacing some bulbs at home with incandescent or near-infrared lighting

• Reconnect with firelight; campfires and candles emit beneficial wavelengths, too.

If light is the key to life, health and well-being, our health-conscious routines should focus on light and the sun. Nicholas argues that getting enough sunlight by being outside, or sitting by a window throughout the day, as well as sleeping in sync with the day-night cycle, can lay the foundation for health from which all other pillars can stand.

Conclusions

The analogy to scurvy is not just poetic. It is prescient. Our ancestors suffered not because they lacked technology or knowledge, but because they were missing a vital input. One that could only be revealed through observation, persistence, and time. Today, we may be repeating history with light.

The latest research reinforces the idea that modern lighting is not neutral. The shift to energy-saving LEDs, while well-intentioned, has stripped light of the broader spectrum our biology expects. The effects are now surfacing, not only in poorer sleep, disrupted circadian rhythms, and chronic fatigue, but also in compromised vision and perhaps even rising metabolic and cognitive disorders.

Just as vitamin C turned out to be essential for life at sea, near-infrared may prove crucial to life indoors. This isn’t an argument against innovation, but a call for smarter, human-centric design; light that nourishes as well as illuminates.

Light is not decoration. It is sustenance. And as Nicholas and others continue to demonstrate, restoring a healthy relationship with the full spectrum of light could be one of the simplest, most cost-effective, and powerful health interventions of the 21st century.