The Bath, the Bins and the Biology of Light

Our bodies evolved under changing natural light. So what happens when we spend our lives beneath a ceiling of artificial illumination? Dr Shelley James, known as the Light Lady, explains why light may be one of the most important — and overlooked — elements of biophilic design.

We often talk about biophilic design in terms of plants, timber, water, natural materials and views of nature. But there is another fundamental element of the natural world that is so pervasive we can easily overlook it: light.

Dr Shelley James, founder of Age of Light Innovations, lighting consultant, educator and advocate for healthier environments, believes we need to rethink our relationship with it. Her message is both simple and profound: light isn't merely something that allows us to see. It is information. Our bodies are constantly reading it, interpreting it and responding to it.

“Every cell in your body is responding to light one way or another.”

Light is one of the strongest signals our bodies receive about what time it is. Deep within the brain, the body's internal clock uses light and darkness to coordinate a remarkable sequence of physiological processes — from alertness and appetite to heart rate, hormones, blood chemistry, muscle function and sleep.

Our internal clocks are not perfectly 24 hours. Left without environmental cues, they tend to drift. Natural daylight — changing in intensity, colour and spectrum from dawn through midday to dusk — continually resets that internal timing system.

This is where biophilic design has an extraordinary opportunity.

We evolved with changing light

Natural light is not static. Morning light is different from midday light, which is different again from the low, warm light of evening. Yet much of the built environment gives us something remarkably unlike this: a uniform ceiling of artificial light that may remain essentially unchanged from morning until night.

And the consequences go far beyond aesthetics.

Shelley explains that the eye is effectively an extension of the brain, and that processing visual information is energetically expensive. The visual system is constantly working out what something is, where it is, whether it matters and whether we need to respond.

There is also another pathway through the eye, involving specialised cells containing the light-sensitive protein melanopsin. These cells are particularly responsive to blue wavelengths associated with the sky and help regulate the body's no