Your Body's Intrinsic Melatonin Rhythm
Melatonin is all the rage, learn what you need to know (Part 1 of 3)
There's a lot of melatonin being used, along with a lot of questions on how to use it best. Plus, some people aren't happy with the results it's getting them. Over the next weeks we’ll talk melatonin in three parts: a) our endogenous melatonin, b) three purposes to take melatonin supplements, and c) considerations for effective use of melatonin. (As ever, this is educational information, and if you wish to take any supplement, check with your healthcare provider to see if it’s right for you).
Whenever we're talking about melatonin, let’s be clear whether we're talking about endogenous melatonin, which is the melatonin that our bodies produce, or talking about melatonin supplements. Today let's start with the natural melatonin in our bodies, that endogenous, or intrinsic, melatonin.
Our Endogenous Melatonin
Melatonin is called the “hormone of darkness.” It’s a compound that is both water and lipid soluble, so can enter all compartments of the body. Each night, in darkness, the pineal gland deep in the brain releases a pulse of melatonin. That melatonin first spreads through the brain, making us drowsy and lowering our core body temperature. Then it goes into the circulation via the blood and is distributed throughout the body.
Most cell types have melatonin receptors. Melatonin binds to our cells, signaling that it is night, and time to switch into night physiology. Other tissues make melatonin too, but there are some key differences. The extra-pineal melatonin produced elsewhere (such as the gastrointestinal tract) stays local, it doesn’t enter the circulation, so only impacts cells that are nearby. The other key difference is that these cells produce melatonin in response to other stimuli, not the light-dark cycle as the pineal gland does.
Light Suppresses Melatonin
Let’s talk more about how melatonin release is intricately linked with our light-dark environment. You’ve probably heard that blue light suppresses melatonin, here’s how it works: In our eyes there are specialized cells in front of the rods and cones which are used for vision. These intrinsically-sensitive retinal ganglion cells measure the wavelength ie. color of light. Across the day, the wavelengths in sunlight change. Morning has more blue light. As the evening approaches, there’s less blue light, and more in the red spectrum. This is the reason for those beautiful sunsets! These special cells in our eyes send information to the brain about what time of day it is. An area of the brain called the supra-chiasmatic nucleus (SCN) gets this time information. The SCN is the “central pacemaker” which sets our circadian rhythm.
Our Nightly Melatonin Pattern
As the sun sets, and the light dims to less than 10 lux, the SCN allows our pineal gland to start to release melatonin. That melatonin continues to rise until about 4 hours into our sleep period, then will start to decline. Interestingly, when we first wake up, our melatonin is still somewhat elevated. But we open our eyes, open the shades, maybe even go outside, and that burst of light quickly suppresses any melatonin that’s still present. Endogenous melatonin levels from the pineal gland are fairly low, about 70pg at most in adults. (For that reason, we consider melatonin supplements of </= 1mg to be ‘physiologic’ doses, while above that are considered ‘pharmacologic’ doses. More on supplements next time, just mentioning it now to give some perspective on dosing vs. physiology).
Melatonin Levels Change Across the Lifespan
Melatonin levels change across the lifespan. Young children have the highest release of melatonin. Starting at puberty, melatonin levels decrease significantly by about 40%. Levels continue to decline in mid-life, so by the time a person is in their fifties they have quite low levels of melatonin.
The Built vs. Natural Environment
It’s important to note that since the wide-spread adoption of the electric light, we have significantly altered the light-dark cues we are getting. This changes our endogenous melatonin pattern significantly. In the built environment melatonin release starts later, and often ends later. This pushes us to be more night-owls. Children are much more sensitive to the negative effects of artificial light at night as their melatonin is suppressed by lower light levels. This is attributed to the fact that their system has not yet aged. (See my previous post about Blue Blocking Glasses for a solution).
Some studies have shown that in a naturalistic light environment compared to the built-in light environment, people in that natural environment end up having melatonin increased for a couple of hours more in the winter nights versus when they're in their homes with electric light.
Notes on Melatonin Testing
An easy way to test melatonin is through saliva. The standard procedure is to collect saliva specimens for six hours before bed. The challenge though is that the person must be in dim light, less than 5 or 10 lux. For most people this is a challenge, and doesn’t reflect their typical lifestyle. Often test kit instructions don’t mention the required light conditions. For these reasons, I question the value of testing your melatonin, unless directed by your clinician to evaluate for a specific pathology.
Sleep Skills
There are reasons – sleep, circadian health, cellular health – that we want to have the normal levels of melatonin that people have in the natural light environment. Here’s a few tips:
Get at least 20 minutes of outside light within the first two hours of your day (Yes, this works even in a cloudy June-uary, as it is here in the Pacific NW!)
Three hours before bed, dim the lights in your home, or wear blue blocking glasses if you need to use electronic screens or use LED bulbs.
Make your bedroom dark for sleep, with a bedside lamp handy if you need to get up.
Next newsletter we’ll talk about melatonin supplements, and when they might be used effectively.
Sleep well and Dream big,
Dr. Catherine Darley
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