Entrainment of Melatonin Secretion Cycles

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It is important to understand when melatonin starts to be secreted in a human with optimal circadian rhythms. That time in the literature when melatonin starts to secrete is typically around 6pm, steadily rises to around 1am when it peaks and then starts to decrease until it bottoms out between 6am – 7am. When melatonin bottoms out, cortisol peaks.



Under the correct light and dark cycles melatonin release can last for about 12 hours. However in our modern world we are exposed to artificial light which causes a shortening of the dark circadian period. What is does is shorten the release time of melatonin meaning we get less quality sleep. When we sleep our bodies go into growth and repair mode. The body will clear out all the dead cells and repair cells that are not functioning properly. With faulty cells not being cleared out of the body they can turn cancerous and multiply. Under artificial lighting conditions after dark our peripheral clocks can become “worn out” which is characterised by a circadian clock that is entrained too late coupled with bright light exposure too early. This of course is all in relation to the time the low lux light exposure started in the evening time (aka – the time you out your BLUblox blue blockers on).

However, it’s not all about artificial light. If you get inadequate morning light you can phase shift melatonin production. The most common incidence of this would be Seasonal Affective Disorder (SAD). Something I suffered with when living in the UK during the winter months.

The Master Clock located in the SCN is amazing and regulating melatonin secretion at the correct times of day, but it can easily become out of sync. Exposure to bright light at the wrong times of day, aka just before you go to sleep and completely suppress melatonin production. Specifically light in the mid blue and mid green ranges 450-550nm. Melatonin is the starting pistol for the body to slowly enter repair mode. Suppressing melatonin tells the body to enter a period of productivity and activity. This can be catastrophic for your sleep and health. Repair does not perform optimally which leads to metabolic diseases such as cancers. The odd late night or light exposure after dark is okay but done chronically will lead to a whole host of metabolic issues later in life.

We understand that light timing is essential for entrainment of our circadian clocks. High lux light exposure in the early mornings allows for melatonin production to occur earlier in the next 24 hour cycle. High lux light exposure in the evenings creates a delay in the production of melatonin in the following circadian cycle.

The spectrum of light also has a big effect on entrainment. Sunlight for example is the perfect blend across the spectrum enabling us to have a well synced circadian cycle. LED light, used when the sun is hidden can actually cause secretion of melatonin to start too early as the spike in the 450nm blue range tells the body its midday already, not early morning. This can lead to circadian mismatch diseases and dysfunction.

No matter where you are in the world the key is to simulate 12 hours of darkness. By simulate we mean removing the melatonin suppressing blue and green light from 400-550nm. This will allow for a correctly entrained circadian clock when coupled with the correct high lux light in the morning. Darkness can be realized in the presence of yellow, amber and red light as they do not impact melatonin secretion.

If you are falling asleep too late it means your light hygiene in the evenings is on optimal. You may be using a lot of technology and not wearing blue blockers. You could be wearing blue blockers that are only blocking blue or some blue light. It is very clear that mid-point green light between 500-550nm also suppresses melatonin so you may need to upgrade your blue blockers.

If you are waking too early (before 06:00) you have not had adequate morning light exposure. It may be difficult in the winter months given factors such as daylight savings time and cloudy weather, so you need to hack your light environment to make sure you get the correct or as near correct spectrum of light as you can in the mornings. Use red light therapy in combination with warmer light bulbs to simulate the sun rising. Don’t get me wrong nothing will ever replace the sun but hacks like these can keep your circadian health in check into the sun starts to reappear seasonally speaking. devises Summer months make it so much easier but we need to understand the above in order to hack our individual lighting environments to get as close to optimal as we can.

View BLUblox range of 550nm blue and green light blockers to get your melatonin entrainment perfected. 

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