Who doesn’t want healthy digestion? Of course most people would answer that they do, but most people take healthy digestion for granted. Who could really blame them, who ever thinks about their digestion until something goes wrong with it?
For the most part, digestion is just one of those automatic processes we never give a second thought to. It’s just like heart rate, blood pressure, breathing rate, and sleep. These things probably never enter your stream of consciousness until something runs amok with one of them.
Circadian rhythms exert a substantial amount of control over digestion and all of these processes. Whether disruption of circadian rhythms is a cause or effect of digestive disorders, if you’re having problems, correcting them can improve your situation immensely. So let’s take a look at how circadian rhythms promote healthy digestion.
What are circadian rhythms?
Circadian rhythms refer to physiological processes that follow an approximately 24 hour rhythm with or without exposure to environmental cues. For example, you go to sleep every 24 hours, so your sleep/wake cycle follows a circadian rhythm.
We all know that light exposure regulates sleep, but did you know that even in the complete absence of light, you’d still have a sleep/wake cycle that follows a 24 hour cycle? For most people it’s a little more or a little less, but it doesn’t really go to 22 or 26 hours.
This inherent rhythm that occurs in the absence of environmental cues is called the free-running clock. Regardless of the cycle your free-running clock runs at, exposure to environmental cues helps reset the clock every day. This is how we’re able to move across time zones and adapt to a new environment with a time relatively different than the one we were previously in. It takes a few days, but we adapt.
The most important concept to grasp with regard to circadian rhythms is that every organ and tissue in your body has its own clock. Optimal function of all organs and tissues and synergy between them is dependent on synchronizing these clocks together and tying them to the day/night cycle. When they become de-synchronized, this is referred to as circadian disruption.
Factors that lead to circadian disruption
There are a few factors that can lead to circadian disruption, but the classic case is jet lag. Jet lag is literally circadian disruption, and resolves once synchrony between the environment and your clocks is re-established. In the meantime, you feel like garbage because your body is like an orchestra without a conductor, or 10 different conductors that are all following their own beat.
Working night shift is another way to disrupt circadian rhythms. To some extent you can do things to lessen the negative impact working night shift has on circadian rhythms, but since you’ll always be out of sync with the Day/Night cycle you still won’t function optimally. And if you think you’re going to break your night shift schedule on the weekends to hang out with friends, think again.
Probably the biggest and most common way to disrupt circadian rhythms is to get older. As we get older, we’re more prone to circadian disruption as our once smooth rhythms become fuzzier. It should come as no surprise, then, that circadian rhythms are associated with all of the chronic diseases of aging. Whether they’re a cause or effect of disease, not paying attention to them will certainly make your disease worse.
Fortunately, our clocks are able to be reset by environmental cues and this doesn’t go away with age. Utilizing these cues to your advantage can go a long way to improve the circadian disruption that comes with age. Since digestion also tends to decline with age, there’s a pretty good chance that correcting circadian disruption will dramatically improve your digestive health.
Circadian rhythms and gut health
So now that we have the basic review out of the way, just how much control do circadian rhythms exert over our digestion? The following digestive processes are under direct circadian control:
- Stomach acid synthesis and secretion
- Bile synthesis and secretion
- Pancreatic enzyme synthesis and secretion
- Brush border enzyme synthesis and secretion
- The migrating motor complex(Housekeeper of the gut)
- The microbiome changes and interacts with the cells in your gut in a circadian manner
- Tight junction protein expression(Gut “leakiness”)
- Toll-like receptor expression(Sensitivity to inflammation)
- Colonic motility(And thus stool consistency)
So, when it comes down to it, basically the entire digestive and absorptive process are under direct circadian control. But it gets even more powerful than that. The entire purpose of having synchronization of the circadian clocks between distant tissues is so that they can work together to make the whole system function properly.
A great example of this is bile. We use bile to emulsify fats, help regulate the “leakiness” of the gut, to promote the growth of beneficial bacteria, to prevent the overgrowth of pathogenic bacteria, and absorb fats and fat soluble nutrients. Bile is made out of cholesterol which follows a circadian rhythm set by the master clock via light exposure.
With every meal we eat, bile gets secreted in to the small intestine from the gallbladder a number of times. The vast majority of this bile, approximately 95%, is recycled back to the liver, resent to the gallbladder, and re-secreted multiple times between meals to help fully digest and absorb our food. The movement of bile from the liver to the gallbladder as well as the recycling of bile acids is regulated by cortisol, which also follows a circadian rhythm that is regulated by the master clock.
As you can see, circadian rhythms truly help tune your body like a conductor tunes a symphony orchestra. Letting just one thing get out of sync with the others can have a devastating effect on how you digest your food. Syncing your clocks together and to the day/night cycle is probably the most important step in re-establishing good gut health when it goes awry and preventing your gut health from going down the tubes in the first place.
Note: I’ve covered this topic in much more detail in a blog you can find here. But if you’re looking for something a little simpler and more actionable, check out my 5 nutrition strategies to optimize your circadian rhythms. You can sign up to receive it at the link below.