Cues for our circadian rhythm come from our environment. The dominant cue is light and darkness. But another significant cue is the timing of eating.  Let’s find out more.

Disruption of our circadian rhythm has been linked to many disease processes, including metabolic syndrome, obesity, cardiovascular diseases, neurodegenerative disease, intestinal dysbiosis, inflammatory bowel disease, and cancer. 

Intestinal cells circadian rhythm

We hear a lot about the hormone melatonin in the brain and it’s involvement with our circadian rhythm, and I’ve written several blog posts about melatonin before. But what is interesting is that melatonin levels are actually much higher in the gut than in the brain. And the gut cells have their own circadian rhythm. These rhythms influence nutrient absorption, gut motility, metabolism, and cell proliferation.  Thus it makes sense that research has found that circadian rhythm disruption is linked to gastrointestinal diseases such as IBS and colorectal cancer.

Gut microbiota circadian rhythm

But layered on top of the individual gut cell rhythm is the circadian rhythm of the microorganisms that make up our gut microbiota. Yes, they too have their own rhythm, as we saw in my earlier post on how the body’s physiology changes during light and dark. Just like our circadian rhythm changes metabolism, so does the circadian rhythm of the microbiota. The levels of different microbes also vary during the day and night. Their changes then affect us too. 

Synchronizing the different rhythms 

The rhythm of the microbiota affects the rhythm of our intestinal cells which affects our body’s rhythm.  We want it to be coordinated, like a dance. So what can we do to synchronize these rhythms and thus help prevent disease associated with circadian rhythm disruption? 

Meal timing

While light exposure is the dominant cue for the body’s clock, the timing of food intake influences our intestinal and microbiota rhythms. 

Eating late at night or during the night and eating at erratic times can disrupt both the intestinal and microbiota rhythms. Conversely, modifying when we eat can bring us back into rhythm. 

One approach to maintaining a good gut rhythm is time restricted eating (TRE) or time restricted feeding (TRF) as it is also known. This approach limits the time you can eat food into a window of  a specific number of hours each day. In its simplest form, it means you eat during 12 hours of the day and fast for the others 12 hours.  So if you wake up at 8 am and eat breakfast, you then stop eating at 8 pm and don’t eat again until 8 am the next morning. This is a relatively easy approach to do.  TRE is found to restore our circadian rhythm in the intestine and thus helps synchronize the body’s rhythm. 

For optimal health and to help heal from illnesses, additional benefits can come from reducing the eating window time more. An example would be fasting for 16 hours and eating over 8 hours. In its simplest form, this means skipping breakfast. I’ve written about this in previous blog posts so take a look if you are interested. (This extended  16: 8 hour fasting approach isn’t suitable for everyone so check the link to the previous blog post and talk to your healthcare professional). 

The 12:12 is a great place to start, however, and may be all that you need. 

Genetics impact gut–circadian rhythm

Genetic polymorphisms in the CLOCK genes can also affect circadian rhythms. Polymorphisms may make some people more susceptible to circadian rhythm disruption and gut health issues such as dysbiosis. For these people, it is increasingly important to have good sleep habits and focus on optimizing your circadian rhythm to keep their bodies functioning optimally.

Take home points

While ensuring a good light vs dark cycle helps with your body’s circadian rhythm, we can support that further by eating and fasting during specific times of the day, for example using 12-hour windows for eating and fasting. This supports our gut and microbiota circadian rhythm which synchronizes with the body’s rhythm.

If you have polymorphisms in your clock genes, this may be a higher priority for you.

Paying attention to these factors may help reduce gut issues, cancer, obesity, cardiovascular diseases and neurodegenerative disorders. 

What eating window can you start with tomorrow?  Don’t view it as something temporary.  Just decide on maybe that 12:12 hour split and make it part of your lifestyle. 

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