Image by Monoar Rahman Rony from Pixabay
When an electronic device stops working, what’s the first thing that most of us think to do? Reboot. Hit the reset button. It’s a beautiful solution, because it doesn’t require you to know what’s wrong… often the problem just fixes itself.
I wrote here on how fasting can function as an overall physiologic “reset button”, and here on how it can specifically regenerate immune cells. Here’s a quick video overview on some of its many health benefits.
Studies show that it can also help hit a “hard reset” on the circadian rhythm, as well. But what does that mean? How does the circadian rhythm actually work?
The Master Clock
The hypothalamus in the brain is considered the body’s master endocrine gland. Contained within it is a structure called the suprachiasmatic nucleus (SCN) which functions as the body’s “master clock,” controlling functions connected to the 24 hour sleep/wake cycle such as eating, drinking, body temperature, and secretion of certain hormones. Triggers that affect this rhythm are called zeitgebers (the German word for “time giver”).
Light, of course, is the most important of the zeitgebers, and probably one of the most common ways it can be disrupted is through artificial light prolonging “daytime” signaling to the brain (and I wrote here on the potential health impacts of artificial light on health). Night shift workers are also at risk, as are those living in polar regions.
The 24 hour cycle of darkness and light seems to be very important, then. This interesting study subjected a flowering plant to both shorter and longer light-dark cycles (20 hrs and 28 hrs, respectively), and found that in both cases, its growth was reduced by half.
Interestingly enough, the SCN “master clock” is so important that grafting a normal SCN into a lab animal whose clock is “off” will restore a normal rhythm to that animal. (Might this suggest that hypothalamic glandular supplementation could have a similar effect?)
The Second Messengers
How does the SCN carry out its mission with respect to the rest of the body? It appears that the SCN functions as the manager, and sends its messengers to peripheral tissues, instructing them what to do. It sends different messengers depending upon whether it’s daytime or nighttime, though (the daytime messengers are called pituitary adenylyl cyclase-activating peptide (PACAP) and cAMP, while the nighttime messengers are the neurotransmitter acetylcholine, and cGMP). Each of these triggers a cascade of events that ultimately causes a “phase advance,” which I envision as shifting the needle forward on a timeline, so that the body gets the message that it’s either daytime or nighttime, and behaves accordingly. The nighttime messengers get inhibited by two things: light (back to the artificial light thing) and glutamate, an excitatory neurotransmitter that opens calcium channels.
Chronically high levels of glutamate is associated with excitotoxicity in the brain which, among other things, is connected with chemical sensitivities and EMF sensitivity. This implies that one of the effects of these conditions may well be circadian disruption.
The Peripheral Clocks
The “worker bees” on the periphery are the cells in the various body tissues, each of which receives the messages that ultimately come from the SCN and behave accordingly. Within these cells, proteins called core clock proteins regulate which genes should get expressed, depending upon the perceived time of day.
These proteins control up to 10% of all genetic expression. (That’s a lot!)
Fasting and the Circadian Rhythm
Considering how important the circadian rhythm is to overall health, if the SCN or the core clock proteins ever lose time, how do you hit the reset button?
One way is with fasting. This is because food also acts as a zeitgeber for core clock proteins, affecting the expression of quite a number of different genes.
The lack of the “food” zeitgeber, even for just 24 hours, can serve as that hard reset button. Then the peripheral tissues and the SCN can sync back up again when re-feeding begins.
The Upshot
Among its many other health benefits, short fasts can also help to “reset” a circadian rhythm gone astray. This has implications on much more than just sleep, since so many different cellular functions oscillate based upon the time of day.
This may be one of the reasons why fasting can have such a profound effect upon overall health.
