Why is Natural Light Important to Humans?

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To understand why natural light is so important, we need to think of our ancestors.  Before we had electrical light humans spent 90% of their awake hours outside. Being outside they were surrounded by natural, dynamic (constantly changing) light.  They enjoyed the warm sunrises, bright blue mid-day lighting and then the warm glow of sunsets. Once inside they had the warm light from candles or fires.  

Our biological time clock, Circadian Rhythm, is reset each day by natural lighting.  As we fast forward to today, we are spending more than 90% of our time indoors under static (non-changing) light.  A study done by UNC Kenan-Flagler Business School found that the color temperature of the light source has the most influence on how we work.  They believe that it’s in our DNA to perform better under specific lighting.

ipRGC

Our eyes are amazing and we now realize that they are for so much more than just vision.  In 2001 Intrinsic Photo Receptive Ganglion Cells were discovered.  In addition to the rods and cones which enable us to see colors and focus, as well as to make out shapes and contrast in dim lighting, these ipRGC’s have nothing to do with our vision. 

87% of our sensory information received is by sight, 50% of our brain is used for vision and yet within our eyes are also these ganglion cells, many of which we still don’t know what functions they perform.  We now do know that the ipRGC’s send information to the part of our brain associated with short term memory as well as our circadian rhythm.  These ganglion cells absorb light, especially blue light which is essential for the entrainment of our circadian rhythm (see blog on Circadian Rhythm). 

There is so much more to learn about our eyes and how they influence our health, with the discovery of these ipRGC’s we have gained the understanding that our eyes are essential for many of our biological functions. 

Circadian Rhythm

Diagram By NoNameGYassineMrabetTalk  ✉   fixed by Addicted04 - Wikipedia

Diagram By NoNameGYassineMrabetTalk fixed by Addicted04 - Wikipedia

Circa-about   dia- day

These are our natural rhythms that repeat in about a 24 hour day.  These are vital for our health and are able to get out of sync – just think of jet lag.  Our circadian rhythm is reset every day – this is called entrainment.  To reset we need bright light in the morning to signal the production of serotonin, and we need dimming light and darkness at night for the production of melatonin.  Both light and darkness are essential for a healthy circadian rhythm.

So many aspect of our lives are regulated by our circadian rhythm, our sleep, mental functioning, emotions, state of mind and many aspects of our immune system and health. 

How can we adjust and improve this essential part of our biology?  Bright light in the morning upon waking, being outside in daylight for at least 20 minutes a day preferably around noon time when the sun is the brightest, exercise, a shift in indoor lighting in the evening to a softer yellower light and avoiding the blue light from electronics for at least 1 hour before bedtime.  Sleeping in total darkness is also important and getting 8 hours of sleep a night, our ancestors before electricity got 10 hours. 

Some current research is suggesting that healthy sleep and a healthy circadian rhythm is an important factor in preventing many of the disease that plague us, heart disease, cancer, obesity, diabetes and Alzheimer’s disease. 

LightFair International 2016

Last week I spent 5 days in San Diego attending LightFair International 2016.  This is an annual lighting conference to show case the newest technologies in lighting.  There are many educational classes during this conference and this year was the first time that they offered a series on Lighting and Health.  I attended a number of these offerings and am so excited about what I learned and saw on the trade floor.  HCL- Human Centric Lighting is here!  Several vendors showcased their Tuneable LED's, which are able to be programmed to change color from warm whites to cool whites to more closely match outdoor light and enhance our circadian rhythm. The classes I attended had studies that showed improvement in productivity, in sleep, and in the lives of people living with Alzheimer's disease with the use of tuneable LED lighting.  So much of this knowledge and the products are cutting edge.  I am looking forward to more products being available for both commercial use and use in homes.