Light, Melatonin and Modern Living

One of the true pleasures of the summer has been eating dinner on our deck and enjoying the long summer evenings.

Something that we take for granted is that modern life is largely lived indoors- but of course for most animals on the planet life is lived very much outside and even for us ‘human primates’ this is a very recent development in our evolutionary history. Of course living and working indoors is a pretty handy development for most of us but like all changes from our natural patterns it has some consequences.

One of the major effects is that we are partially removed from the natural rhythm of light and dark that helps to regulate our endocrine systems in their daily cycles. Living indoors means that we aren’t exposed to as much light during the day as we would be if we were largely outdoors and then using artificial sources of light in the evenings mean that we are exposed to more light in the evenings than we naturally would be. There is no question that this can significantly disrupt the way our brains and bodies function.

Here’s how the Neurology works: Our retinas have specialised cells (called ganglion cells) which aren’t used for vision but act to detect the intensity of the light passing through the eyes. These cells have nerve connections directly back to a part of the Hypothalamus gland (called the Suprachiasmatic Nucleus) this in turn controls the release of Melatonin from the Pineal gland. When you have a lot of light passing through your eye, melatonin release is suppressed – this makes you feel more alert. When you have low levels of light passing through your eye, the pineal is triggered to release more melatonin – and you feel sleepy.

Disruption of the natural cycle of melatonin can cause problems with sleep and consequent fatigue. Melatonin is also thought to play a role in conditions as diverse as cancer, immune disorders, cardiovascular diseases, depression, seasonal affective disorder (SAD), high cholesterol, obesity, anxiety, memory problems, and chronic fatigue syndrome. Melatonin is also an anti-aging hormone and has been shown to decrease age related degeneration and improve life expectancy in experiments on mice.

To help to regulate your melatonin production, think about when you are exposing yourself to bright lights. Research has shown that exposure to normal room light levels in the hours prior to sleep can reduce melatonin production by up to 50% resulting in difficulties falling asleep and less restful sleep. Also studies have shown that staring at a light source such as a TV or a computer screen in the evening supresses melatonin production. In one study participants who used a tablet computer for 2 hours in the evening had a 22% reduction in melatonin levels.

So what should we do about it?

Well electric lights and working indoors are here to stay but we should all be making an effort to get at least 30 minutes of natural light exposure every day and when we are inside we should keep things as light as possible.

Conversely, in the evenings try and dim the lights as much as is practical and turn down the brightness on your TV and computer screens. If sleep is an issue for you then you should definitely avoid bright lights and TV/computer screens for 90 minutes before bed.

Yes, that’s probably a slight inconvenience but I reckon it’s worth it for a refreshing night’s sleep.