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The gut microbiota, circadian rhythm and dietary patterns...what is the connection?

Alcohol and fast food consumption at night lead to a disruption of gut microbiota rhythmicity which may lead to intestinal inflammation and an increased risk of certain colorectal cancers.

We’ve all experienced a late night of partying followed by a dose of fast food in the early hours of the morning. And we’ve all been so busy with work that we don’t have time to sleep or eat. But did you know these behaviors can have a negative impact on your gut microbiota health?

Diet is the factor that has the greatest impact on your gut microbiota and a new review led by Dr. James F. Cheeseman from the University of Auckland (New Zealand) highlights that your eating and sleeping patterns are also connected to gut bacteria and health.

So how can these behaviors affect your gut microbiota?

The circadian rhythm regulates our body’s energy expenditure, appetite and sleep. In simple terms, it is our internal clock. Under normal conditions, people get around seven hours of sleep per night. Then, as you wake, your body warms up, using up energy as you move around and carry out your daily functions. Your body needs food during the day to give you this energy, then at night-time, it fasts and goes to sleep.

Researchers noted that the basic rhythmicity of the gut microbiota is described by an increase of Firmicutes during feeding periods followed by its decrease over time during the day. Although some gut bacteria such as Bacteroidetes, Proteobacteria and Verrucomicrobia are more present during fasting periods, bacteria that feed on fiber grow at night as food residues reach the colon. Polyphenol and some prebiotic fibers such as GOS (galactooligosaccharides), found in plant sources and breast milk, respectively, are able to consolidate the circadian rhythm by increasing gut microbiota diversity.

Gut microbiota rhythmicity is expressed through the secretion of molecules at specific times of the day. At night, genes related to energy metabolism, DNA repair and cell growth are enacted, while during the day, bacteria produce molecules that consolidate their own colonization of the gut.

As reported by the authors, night fasting is beneficial to gut microbiota given the production of molecules called short-chain fatty acids, such as butyrate, which protects our gut and also regulates glucose levels through various glucose-related hormones, or propionate, which regulates fat metabolism in the liver. Meanwhile, microbial metabolites excreted during feeding time are related to proteins and lipids absorption. Nutritional tryptophan is converted to serotonin, a molecule which regulates our gut motility, but studies have found it to be correlated with the production of melatonin (sleeping hormone). Moreover, a new tryptophan transport mechanism has found it to be transported to the brain with impact on cerebral functions such as sleep.

According to the review in Microorganisms, sleep time controls the rhythmicity of our food intake through feeding and fasting actions. Any long disruption to this cycle may contribute to an unbalanced gut microbiota, which may lead to a higher risk of metabolic diseases such as diabetes and obesity. Researchers highlighted that alcohol and fast food consumption at night lead to a disruption of gut microbiota rhythmicity through a fall in the number of Bacteroidetes, which may lead to intestinal inflammation and an increased risk of certain colorectal cancers. Furthermore, the higher fat content present in fast food promotes bacteria that can resist the molecules that come from digestion, and many of them are pathogenic or pro-inflammatory due to their ability to produce toxins.

Interestingly enough, studies have shown that ingesting probiotics may help increase melatonin secretion and sleeping quality, opening a door for the future use of probiotics for sleep regulation and health.

In conclusion, both your diet and your lifestyle can affect gut microbiota health and balance. A healthy diet that is high in fiber and a regular eating schedule during the day are tools we can easily access for improved gut microbiota rhythmicity, meanwhile behaviors that include eating late at night, alcohol consumption and sleep disruption need to be avoided.

This article was originally written by: Manon Oliero

Referenced in the article: Parkar, SG, Kalsbeek, A, Cheeseman JF. Potential role for the gut microbiota in modulating host circadian rhythms and metabolic health. Microorganisms. 2019; 7(2). doi: 10.3390/microorganisms7020041. -


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