Circadian Cycle: How Sleeping Too Little or Eating Late Can Affect Gut Health

Just like we have a daily routine (eat, work, exercise, sleep), our body has one too.

This is the circadian cycle. During the morning and afternoon, the body and mind are active; as night falls, a series of physiological changes prepare us for sleep.

It’s like a clock. An internal clock that warns us of the different moments of the 24 hours of the day and that has both a physical, mental and behavioral impact.

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It is not difficult to understand the importance of this mechanism. Anyone who’s ever stretched late, on a night out, or had one of those busy days at work where there’s no time to eat or sleep well, has felt the consequences.

The truth is that the Western lifestyle does not help keep the circadian rhythm balanced.

We are exposed to fewer hours of natural light than our ancestors: we are more sedentary and spend more and more time in front of screens.

Added to this is a higher level of stress, a social life that does not respect our routine hours and a diet based on sugary and ultra-processed products.

What implications could all this have for health?

An imbalance can lead to lack or poor quality sleep, mood swings, increased stress, disorientation, memory problems, fatigue and anxiety, among other evils which, if maintained for a long time, can have much more serious consequences. .

Changes in meal times also interfere with the body clock — Photo: Getty Images via BBC News Brasil

Bacteria and their biorhythms

But circadian rhythm disturbances aren’t just about us — they’re also affected by our gut bacteria, which have their own cycles, synchronized with ours.

So, can a mismatch in our internal clock affect our gut health? Definitely yes.

Disturbances in physiological cycles are closely related to changes in the digestion process and metabolism.

They can be caused, for example, by an imbalance in glucose metabolism, which increases the risk of weight gain and increased blood pressure, as well as a deregulation of hormones that control appetite and favor foods high in sugar and saturated fats.

This can cause decreased insulin sensitivity, lower glucose tolerance, and a change in the body’s lipid profile. These are alterations that have a direct impact on intestinal health and, therefore, on the microbiota.

And it’s no wonder that this relationship occurs, given that the digestion of food takes place during the day, when the intestine remains active and in optimal conditions for absorbing nutrients.

When we eat, we synchronize the clocks of the organs and tissues involved in digestion: the stomach, pancreas, liver, intestines and adipose tissue.

Changes in the microbiota may affect gut health — Photo: Getty Images via BBC News Brasil

Change of schedules, change of microbiota

And what happens to the microbiota if, for example, we start eating late?

Eating a late meal, which usually occurs at noon, for example 4 pm, causes a delay in the clock, an interruption of the normal rhythm of intestinal function and a change in the composition and functionality of intestinal bacteria.

The microbiota is mainly influenced by the profile of our diet, but changing feeding times, whether it is for behavioral reasons, fasting or increasing the frequency of meals, also has an impact.

Intestinal bacteria show their own fluctuations depending on the time of day, both in composition and function.

Scientific evidence underlines that, in fact, they have their own circadian cycle, which they try to synchronize with that of the host to make the most of it.

Most of the research on the microbiota and circadian cycles has been conducted in animals.

There are studies focused on, for example, intermittent fasting that have revealed some benefits in mice, such as increased microbial diversity, reduced inflammation and the production of beneficial compounds by gut bacteria.

In humans, a study with women found that eating late reversed the rate of oral microbial diversity. What appears is a pattern also seen in some diseases, including obesity and inflammatory bowel disorders.

It should not be forgotten, however, that the gut microbiota is like a unique and personal signature of each individual, so that each person responds differently to both intermittent fasting and changing meal times.

The influence of microorganisms on our sleep

These studies show that the gut microbiota is affected by a mismatch in biological cycles, as these turn genes involved in bacterial metabolism on or off depending on the time of day.

However, this is a two-way relationship: even the metabolism of intestinal bacteria is able to influence the circadian rhythm.

This process can occur in two ways: through the production of metabolites, from the food we eat, or by responding to changes in the weather by modulating the abundance of certain bacterial groups.

The gut microbiome is responsible for producing some of the chemicals (the related metabolites) that end up in our bloodstream and can induce or promote sleep.

Bacteria synthesize these substances from the food we eat and when we eat it, thanks to their own metabolism.

For example, Streptococcus bacteria and some strains of Escherichia and Enterococcus contribute significantly to the production of serotonin, linked to the sleep-wake cycle.

Another neurotransmitter, gamma-aminobutyric acid (coming from the fermentation of dietary fibers by the microbiota) helps to promote sleep through an action on the sensory mechanisms of the portal vein of the liver (vessel that carries blood from the intestine to the liver ).

Our microbial community can also respond to disruption of the circadian cycle or its low quality by interfering with the quantity of certain bacterial groups.

In extreme cases, a state of dysbiosis can be reached, i.e. the dominance of harmful bacteria over beneficial ones.

To provide more insight into the effects of deregulation of biological rhythms, researchers from the Federal University of Pernambuco (UFPE) and the Spanish institute IMDEA Alimentación (Madrid) are working together.

The aim is to study the fasting and feeding cycles in the gut microbiota, the effect this can have on obesity and the search for bacterial biomarkers of food intake in the Dietary Deal and Metainflamacion projects.

*Amanda Cuevas Sierra is a postdoctoral researcher at IMDEA ALIMENTACIÓN

*Alfredo Martínez Hernández is director of the Cardiometabolic Nutrition and Health Research Program and of the Cardiometabolic Nutrition Group at IMDEA ALIMENTACIÓN

*Elizabeth do Nascimento is a professor in the Department of Nutrition at UFPE and in the Bachelor of Nutrition at UFPE in the research line of experimental nutrition and metabolism

*Nathalia Caroline de Oliveira Melo is a PhD candidate in Nutrition at UFPE in the area of ​​experimental nutrition, intestinal microbiota and chrononutrition

**This article was originally published on the academic news site The conversation and republished under a Creative Commons license. Click here to read the original version (in Spanish).

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