In this insightful podcast discussion, friend of the podcast, Professor Glen Jeffery, sheds light on his recent study published in Nature (https://www.nature.com/articles/s41598-026-35389-6)

Introduction
In a world dominated by LED lighting, we often overlook its potential health consequences. Professor Glen Jeffery's groundbreaking study highlights the significant effects of artificial lighting on our vision and overall metabolic health.

The Research Background
Professor Jeffery begins by addressing growing concerns about how artificial lighting affects our health, particularly in environments with scarce natural light. The study was conducted in a building at University College London. The hypothesis was that the lack of natural light and the prevalence of LED lighting could be detrimental to overall health, particularly in terms of colour perception and metabolic functions.

The Experiment
The unique aspect of this study was its real-world setting. Instead of a controlled laboratory, the researchers chose an office environment where participants would typically work. Participants were given old incandescent light bulbs, which emit a broader spectrum of light, including infrared, crucial for metabolic health.

Surprising Results
The results were striking: participants showed a highly significant improvement in their vision after only a short exposure to incandescent lighting. This improvement persisted for months after the bulbs were removed, suggesting that exposure to a broader spectrum of light is vital for visual and metabolic health. Professor Jeffery emphasised that this study is a wake-up call about the damaging effects of LED lights, which may suppress our physiological functions, including colour vision.

The Importance of a Balanced Light Spectrum
Professor Jeffery highlighted that while LED lighting is often considered energy-efficient, it poses risks to human health by limiting the spectrum of light we are exposed to. He discussed the need for architects and lighting engineers to rethink building design, emphasising the importance of incorporating a wider spectrum of light for optimal health. The study also raised concerns about the glass materials used in buildings, which block essential infrared light.

Moving Forward: Practical Solutions
To address these challenges, Professor Jeffery suggests we don’t need to eliminate LEDs entirely. Instead, he advocates a balanced approach to lighting by integrating incandescent bulbs into our environments. Simple measures, such as using incandescent bulbs with dimmer switches, can mitigate the negative effects of LED lighting. He also urges policymakers to rethink regulations surrounding incandescent bulbs to ensure a healthier future.

Key Takeaways

1. LED lighting may impair our vision and metabolic health.
2. Exposure to incandescent bulbs can significantly improve colour perception and overall well-being.
3. A balanced approach to lighting, incorporating a variety of light sources, is essential for our health.
4. Policymakers must prioritise health implications when designing lighting regulations.

The paper is available for download here: https://www.nature.com/articles/s41598-026-35389-6

Sunlight Matters is a podcast exploring the role of the Sun in human health, architecture, cities, and everyday life.

Through conversations with scientists, architects, and technologists, the series examines how natural light shapes our bodies, our buildings, and the way we live indoors.

Hosted by Dave Wallace, Sunlight Matters asks a simple but overlooked question: what happens when we disconnect from the Sun?

Because sunlight isn’t optional. It matters.

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In this episode of Sunlight Matters, Dave sits down with the brilliant Paula Longato—architect, daylight consultant, and lighting designer—to explore why daylight access and sunlight analysis are critical yet often overlooked elements in urban design and architecture.

🎙️ What You'll Learn:

• Why modern cities like New York and Dubai are "dark daylight cities" 🌆
• The role of shadow mapping and solar exposure in creating healthier urban environments
• How real estate sun studies can shape better buildings and energy-efficient homes
• The silent power of green light, and how vegetation affects our mental and physical health 🌿
• Why vernacular architecture holds the key to future-ready, climate-conscious cities
• The untapped potential of darkness design and the physiological dangers of over-illumination 🌒

💡 Paula shares her journey from sun-soaked São Paulo to the grey skies of Germany—and how that shift sparked a lifelong passion for daylight architecture and sunlight-responsive urban planning. Together, they tackle the complexities of building orientation, facade engineering, and circadian lighting, offering a holistic view of how we can—and must—build better with the sun in mind.

🌇 Whether you're an architect, city planner, homebuyer, or just someone chasing sunlight, this episode will shift the way you think about the built environment and your place within it.

Dave sits down with Ulysse Dormoy, CEO of Atrium Ltd, to explore a subject hiding in plain sight: the light we live under every day — and how it’s quietly impacting our health, performance, and wellbeing 🌞🏙️

What starts as a conversation about lighting design quickly reveals a much bigger story. From LED flicker and infrared deprivation, to the shocking parallels between ultra-processed food and ultra-processed light, Ulysse shares his journey into the world of light as a biological force.

We dive into:
🔎 How modern offices and homes are robbing us of essential light
🌿 Why sunlight exposure, shadow mapping, and solar orientation matter more than ever
🧠 The science behind photobiomodulation and its rising popularity
🏢 The silent health risks baked into energy-efficient architecture
🚶‍♂️ What designers, planners, and employers can do to build truly healthy environments

You’ll also hear why Ulysse carries a spectrometer everywhere, what happens when beauty brands get lighting wrong, and how we might be heading towards a "lighting tobacco moment" — where health meets accountability ⚠️

Whether you're an architect, designer, developer, or just spend too much time indoors, this episode will change the way you think about light, space, and health forever 🌇