Above: Sun rise at the Trundle, Goodwood, West Sussex – © Keir Watson, 2010

Dawn, dusk, midday. Sunlight cheers the spirits like nothing else. As in the ancient civilisations of South America and Egypt, we all worship the sun in our own way: sunbathers prostrate themselves before it, at bank holidays we pray for its arrival, and everyone simply feels better when the sun is shining.

This urge is natural and healthy. Man evolved in central Africa where there was no lack of sunshine. Moreover, as he left the forests he developed hairless skin, exposing his body more fully to the direct rays of the sun. For millions of years he spent the majority of his day outdoors. Furthermore, as humans moved north to less sunny climates a mutation occurred – white skin – an adaptation that persisted as it allowed better synthesis of vitamin D in regions where the sun was weaker.

It is not surprising then, that there are many aspects of our physiology that are dependent on light. Like the orchids in the picture above, humans too photosynthesise. Not only does sun falling on skin produce vitamin D – an essential hormone – but recently it has been shown that it promotes the release of nitric oxide into the capillaries leading to a lowering of blood pressure*. Another effect comes from the red light of morning and evening which act on the skin, eyes and brain regulating the circadian rhythm and ensuring a good sleep-wake cycle.

A vast body of research is now emerging linking different parts of the spectrum, including ultraviolet and infra-red to a range of health processes. The application of this knowledge is called phototherapy. As most of us now live indoors for the majority of the time, and expose ourselves to artificial light such as fluorescent lights and computer screens late into the evening, an understanding of light and health is becoming ever more urgent. In the articles below I will explain some of the ways that I use phototherapy in my clinic, but will also share some ideas you can easily put into practise for yourself.