Do gut bugs experience jet lag?

Do gut bugs get jet-lagged? Trillions of microbes collectively make up the "gut microbiota", and, according to a study out this month, when the host's day and night cycles and feeding times change, the gut microbiota can change too.

To take a closer look at links between circadian rhythms and the gut microbiota, researchers at the Weizmann Institute in Israel analysed bacteria in the faeces of mice and discovered daily fluctuations in the numbers of microbes and in their activities.

Changing the day/night rhythms of the mice by altering their exposure to light and feeding times led to fluctuations in the rhythms of their gut microbes too. Feeding times emerged as a particularly strong influence, seemingly coupling the body’s internal clocks with the bacteria.

"Here we demonstrate that the gut microbiota itself follows diurnal [24-hour] oscillations in composition and function whose regulation is governed by host feeding rhythms," write the researchers in the journal Cell.

Interestingly, after weeks on a high-fat diet, “jet-lagged” mice gained more weight than “control” mice with normal day/night rhythms. And when the researchers transplanted “jet-lagged” gut microbes into mice that lacked gut microbiota, the weight-gain effects transferred over too.

What about humans? The study found rhythmic oscillations in the gut microbes of two humans studied. And when two healthy humans flew long-haul (US to Israel), their gut microbe fluctuations got thrown off course in the short-term, but were back to normal after two weeks.