Chasing the Sun: The New Science of Sunlight and how it shapes our bodies and minds by Linda Geddes.

Sunlight gives us life and health. It is important to keep our circadian rhythms synchronised and our body functions working properly. It is important for our mood and sleep. It helps segregate important hormones like melatonin, important for our sleep, recovery and repair. It helps to protect childhood short-sightedness, lowers blood pressure, and calms the immune system. 

A problem we have in our modern, western world is that we live indoors (some people fear the sun!) under artificial lighting which might be useful during the day (if you don’t get much sunlight during the day, like here!) but which is extremely harmful during the night. If we don’t see enough daylight, or we are exposed to too much artificial light at night, our bodies become confused and no longer work as efficiently. 

My main takeaways: 

• Regular exposure to sunlight particularly, first thing in the morning, will strengthen our daily rhythms. 
• Sunlight and darkness at night are the main mechanisms we use to synchronise our internal rhythms to the external time of day. 
• Artificial/LED lights can enable “some” (not all) of the effects of daylight indoors. 
• Light in the evening and night -> delays our clocks. We feel sleepy later. Light in the morning -> advances the clock and makes us want to sleep earlier the following evening. 
• The light we receive indoors, office lighting for example, would be the equivalent to twilight outdoors. Sunlight, even on a gloomiest winter day, is ten times brighter than artificial light. 
• Tools to deal with depression and SAD: bright light in the morning, sauna, and cold water. 
• Circadian lighting system – many different colour LEDs can be joined together to vary the shade of light they produce – adjusting colour and intensity according to outside time. 

Other interesting themes discussed: stages of sleep, shift work, jet lag, daylight-saving time and (laws about) access to sunlight in cities. Also, Photodynamic therapy and Heliotherapy.