Have you walked down a suburban street at night and noticed how bright the lights inside some houses are; conflagrations of illumination, mimicking the brightest sunshine.

As well as being a waste of electricity, bright lights can interfere with production of melatonin in our brains, which has an affect on our body clocks.

Melatonin and the human body clock

Melatonin is a naturally occurring hormone that is key to sleep and the sleep-wake cycle in humans and other animals. In the body, melatonin is produced by the pineal gland in the brain when night falls. The retina detects failing light, and the level of melatonin gradually increases, reaching its peak in the middle of the night in natural circumstances.

Our circadian rhythm (or ‘body clock’) is therefore influenced by melatonin. Melatonin is not a sedative, it works as a cue for innate night-time behaviour. In the morning when plasma levels of melatonin decrease, sleep ends and wakefulness begins.

In humans, melatonin induces heat loss, reduces arousal and related brain activity and delays production of cortisol, which increases blood pressure and blood sugar, in preparation for sleep.

Intense light at night interferes with your body clock.

Research indicates that room light exerts a profound suppressive effect on levels of melatonin thus shortening the body’s internal perception of night duration. Hence, regularly exposing oneself to electrical lighting in the late evening disrupts melatonin signalling and could therefore potentially impact sleep, thermoregulation, blood pressure, and glucose homeostasis.

The research results were clear, showing that exposure to room light before bedtime shortened melatonin duration by about 90 minutes, compared to dim light exposure. In addition, the researchers say, exposure to room light during the usual hours of sleep suppressed melatonin levels by more than 50%.

The benefits of muted light

Some people prefer dim lights at night. Soft, muted light is more calming and seems to be conducive to night-time endeavours like reading, writing and hobbies. Of course you need sufficient light to see what you are doing, but this is surprisingly little. Whilst you can’t damage your eyesight by reading in dim light, if the light is too dim you will become easily fatigued.

For centuries people have used candle lamps and oil lamps, and before that people only had firelight. These were all dim lights that didn’t turn the night time into the day time. These light sources simply provided enough illumination so that people could see what was in front of them. The light didn’t do harm to the darkness, it gently spread it away with a soft glow.

Electric lights can be much brighter, and often are. However, most of the light is wasted because it is brightly illuminating rooms that are either empty, or mostly empty. Of course, there is a place for bright lights, an operating theatre for example. But, unless you are planning on operating on one of your family members before heading off to bed, you certainly don’t need those searing lights at home.

As already mentioned, dim light, as opposed to bright light, does not disrupt our body clocks. On the contrary, it seems to help relax us and lets us gently wind down. It’s reassuring warm glow is conducive to reflection, as well as focussing our attention on what is at hand.

Save electricity and your body clock by dimming those lights. You could even light a beeswax candle and enjoy the added benefits of burning beeswax.