Circadian cycle: How too little sleep or late eating can affect gut health

Just as we have a daily routine (to eat, work, exercise, sleep), our body also has one.

This is the circadian cycle. During the morning and afternoon, body and mind are active; with the arrival of night, 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 an impact both physically, mentally and behaviorally.

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

The truth is that the western lifestyle does not contribute to keeping 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 schedules and a diet based on sugary and ultra-processed products.

What implications might all this have for health?

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

Bacteria and their biorhythms

But circadian rhythm disorders don’t just affect us: they are also influenced 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 linked 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, in addition to a deregulation of hormones that control appetite and favor preference for foods rich in sugars and saturated fat.

This can cause a decrease in insulin sensitivity, a 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 is not surprising that this relationship occurs, since food digestion occurs during the day, a time when the intestine remains active and in optimal conditions to absorb nutrients.

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

Change in schedules, change in microbiota

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

Eating a meal later, which usually takes place at midday, for example at 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 affected by the profile of our diet, but changing feeding times — whether for behavioral reasons, fasting or increasing the frequency of meals — also has an impact.

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

Scientific evidence points out 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 research on the microbiota and circadian cycles has been carried out in animals.

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

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

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

The influence of microorganisms on our sleep

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

It is, however, a two-way relationship: the metabolism of intestinal bacteria is also able to influence circadian rhythm.

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

The intestinal microbiome is responsible for producing some of the chemical compounds (the referred 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, bacteria Streptococcus 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 (from the fermentation of dietary fiber by the microbiota) helps to promote sleep through an action on the sensory mechanisms of the portal vein of the liver (a vessel that carries blood from the intestines to the liver).

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

In extreme cases, a state of dysbiosis can be reached, that is, the predominance of harmful bacteria over beneficial ones.

In order to provide more information about 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 objective is to study the cycles of fasting and eating in the intestinal 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 Nutrition and Cardiometabolic Health Research Program and the Cardiometabolic Nutrition Group at IMDEA ALIMENTACIÓN

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

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

**This article originally appeared on The Conversation scholarly news site and is republished under a Creative Commons license. Click here to read the original version (in Spanish).

– The Portuguese version was published here