How circadian rhythms and gut microbiota team up to impact human health

In a review article published in the journal Nutrition, Metabolism, and Cardiovascular Diseases, scientists have provided an overview of recent studies investigating the association between circadian rhythms, gut microbiota, and diet and the collective impact of this association on general health.

Review: Circadian rhythms, gut microbiota, and diet: possible implications for health. Image Credit: T. L. Furrer / Shutterstock

Background

Chrono-nutrition is defined as the relationship between meal timing, circadian rhythms, and metabolic health. This particular field of nutrition has gained immense popularity recently because of the significant impact of circadian rhythms on the host’s metabolic processes and gut microbiota. Circadian rhythms refer to a series of endogenous oscillators generated by the circadian biological clocks that create a link between internal physiological processes and the external environment.

A considerable proportion of total gut microbiota composition fluctuates rhythmically throughout the day. Moreover, the gut microbiota itself synchronizes the circadian biological clocks of the host through different signaling pathways. These observations indicate that there might be crosstalk between host circadian rhythms and gut microbiota and that dietary patterns and timings might play a crucial role in this interplay.

Interplay between diet, circadian rhythms, and gut microbiota

Every aspect of dietary habits, including meal timing, frequency and regularity, and diet quality, collectively play a role in modulating the crosstalk between circadian rhythms and gut microbiota.

Meal timing

The central circadian clock located in the brain is regulated by the sun’s light-dark cycle. However, since peripheral circadian clocks located in the liver, pancreas, and gastrointestinal (GI) tract cannot be directly exposed to light, these clocks are primarily synchronized by dietary components.

Studies have shown that food intake in the late evening can disrupt circadian rhythms (chrono-disturbance) and alter hormone secretion. In addition, each 1-hour increase in the last meal time of the day has been found to associate with metabolic alterations, including increased C-reactive protein, reduced high-density lipoprotein (good cholesterol), and impaired glycemic control and body weight management.

Time-restricted feeding refers to the consumption of a desired amount of food during a specific time period. This particular dietary pattern has been found to modulate gut microbiota composition, such as the induction of beneficial bacterial communities and the reduction of harmful bacterial communities. Such restriction in food access time is believed to mimic natural eating patterns based on circadian rhythms.  

Meal frequency and regularity

Irregular eating habit is known to alter circadian rhythms by desynchronizing central and peripheral circadian clocks. Many studies have found that people who prefer to eat in the late evening hours have a significantly higher tendency to skip breakfast, lunch, or mid-morning snacks.

A study conducted on horses has found that food intake at a higher frequency reduces the abundance of harmful bacterial communities in the gut. However, no study has so far investigated the effect of meal frequency and regularity on human gut microbial composition.

Diet quality

Chronotype is defined as the body’s natural tendency to be awake or asleep at certain times during the day. Evidence suggests that a person’s chronotype can affect his/her diet quality.

Although chronotypes seem to have no effect on the intake of macro- and micronutrients, studies have shown that late-evening eaters have a higher frequency of sucrose consumption than morning eaters. Moreover, some studies have shown that evening-time eating habits are associated with poor or unhealthy diet quality.

The Mediterranean diet is considered one of the best dietary patterns with many health benefits. This diet is known to reduce the risk of cardiovascular and metabolic diseases and all-cause morbidity and mortality. Studies have shown that the morning chronotype is associated with higher adherence to the Mediterranean diet and better body weight management.

Regarding the relationship between diet quality, gut microbiota, and circadian rhythms, studies have shown that high-fat diets alter gut microbiota chronobiology, leading to altered production of microbial metabolites and impaired circadian rhythms and metabolism.

Health impact of diet, gut microbiota, and circadian rhythm crosstalk

Diet-related chrono-disruption and gut microbiota dysbiosis are associated with the development of many chronic diseases, including cardiovascular and metabolic diseases, mental disorders, and certain cancers.

There is evidence showing that evening chronotype is associated with altered cardiometabolic profiles. A significantly altered lipid and glucose metabolism and gut microbiota rhythmicity has been observed among evening-time eaters.

Studies have also found an association between evening chronotype and risk of breast, prostate, lung, and colon cancers. It has been hypothesized that circadian disruption increases cancer risk by altering cell proliferation and sleep cycle. Circadian disruptions can also promote carcinogenesis by changing the production of gut microbial metabolites, such as short-chain fatty acids (SCFA) and bile acids.

An imbalance between circadian rhythm and gut microbiota can increase the risk of certain mental disorders, including depression. This could be due to the altered rhythmicity of neurotransmitters that are associated with mood regulation.

Some recent evidence has suggested that a higher abundance of pro-inflammatory microbial communities and a lower abundance of SCFA-producing microbial communities can alter circadian rhythms, which collectively increase the risk of depression.