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“Have you seen the latest research showing that the microbiome has a circadian rhythm?” asked my friend Dr. Uli Bauhofer. We were talking about my book Gut Crisis and how it relates to Ayurveda, the ancient system of medicine from India. Dr. Bauhofer, who is a highly respected German doctor and an expert in Maharishi Ayurveda, continued enthusiastically, “This helps explain why it’s important to have your main meal at the time of day when your agni (digestive power) is strongest!”

I immediately went to PubMed to look up articles on the microbiome and circadian rhythms. It is well known that most forms of life, from bacteria to humans, have internal molecular biological “clocks” that maintain an approximate 24-hour rhythm. Humans have a master clock located in a tiny group of cells in our hypothalamus (suprachiasmatic nucleus), which synchronizes the many different internal rhythms in our body. This master clock uses external signals from the daily cycles of light and dark to ensure a continuous recalibration of our internal timekeeping to a rhythm of exactly 24 hours. When we introduce abnormal external signals of light and dark, we confuse our master clock and create health problems. For instance, studies show that shift workers have a higher incidence of cancer, cardiovascular disease, digestive disorders, obesity, psychiatric, and neurodegenerative diseases.

Jet lag is a common disrupter of our internal rhythms. Cross several time zones in a matter of hours, causes our internal clock to go out of synch. One scientific study created jet lag in mice by forcing these normally nocturnal animals to stay up during the day. The researchers then tested gut bacteria from the jet lagged mice to see if it would affect germ-free mice, with no bacteria in their body. When the researchers did a fecal transplant (that awful procedure rears its ugly head once again), transferring gut bacteria from the jet-lagged mice into germ-free mice, the recipient mice gained weight. And when researchers transplanted gut bacteria from jet-lagged humans into germ free mice, they developed both obesity and glucose intolerance.

Another study showed that a disruption of circadian rhythms can lead to an unhealthy balance of the gut bacteria, particularly if coupled with a high-fat diet or alcohol consumption. The authors of the study suggest that this unhealthy state would increase the number of bacteria that cause inflammation in the gut lining, promoting inflammatory diseases.

What else disrupts the circadian rhythms of our gut bacteria? Oddly enough, one of the most important issues is when we eat. When animals eat within 2 hours before they normally go to sleep, it can desynchronize the circadian rhythms of certain cells in the intestine and liver from the rest of their body. Chrono-nutrition is a field of study that examines the health benefits of time restricted feeding. For example, studies show that feeding animals on a specific time schedule reduces both insulin resistance and increases glucose tolerance.

At the beginning of one PubMed article, the authors quote medieval philosopher and doctor Maimonides, ‘‘Eat like a king in the morning, a prince at noon, and a peasant at dinner.” This echoes the advice of all well-known traditional systems of medicine. In Ayurveda, as Dr. Bauhofer pointed out, agni or digestive power is said to be highest at noon and decreases as the sun goes down. Because of a new understanding of our gut bacteria, modern science is finally able to verify the ancient knowledge of the value of circadian rhythms for our digestion and health.

 

References:

Reynolds, AC et al., The shift work and health research agenda: Considering changes in gut microbiota as a pathway linking shift work, sleep loss and circadian misalignment, and metabolic disease. Sleep Med Rev 2017; 34:3-9

Paulose, JK, et al., Human Gut Bacteria Are Sensitive to Melatonin and Express Endogenous Circadian Rhythmicity. PLoS ONE 2016; 11(1): e0146643

Voigt, RM et al., Circadian Rhythm and the Gut Microbiome. Cell, 2016; 161(1): 84-92

Zarrinpar, A et al., Daily Eating Patterns and Their Impact on Health and Disease.Trends Endocrinol Metab 2016; 27(2):69-83

Thaiss, CA et al., Trans-kingdom control of microbiota diurnal oscillations promotes metabolic homeostasis. Cell, 2014; 159(3): 514-29

Summa, KC and Turek, FW, Chronobiology and Obesity: Interactions between Circadian Rhythms and Energy Regulation. Adv Nutr 2014; 5: 312S–319S

Deckle-Mahan, K and Sassone-Corsi, P, Metabolism and the Circadian Clock Converge. Physiol Rev 2013; 93(1): 107–135

Konturek PC et al., Gut clock: implication of circadian rhythms in the gastrointestinal tract. J Physiol Pharmacol. 2011; 62(2):139-50