Thinking about travelling this summer to Bali or French Polynesia? Maybe, while you’re reading these lines, you picture yourself lying on a beautiful beach, drinking smoothies, sunbathing and taking dips. Sounds good, really good. But, beware the health problems caused by jetlag during the days after your flight.

Fatigue, sleeplessness, dizziness, sleepiness, hunger and even intestinal problems, such as constipation or diarrhoea. All of these can happen when crossing multiple time zones, due to jetlag: a temporary sleep problem caused when your body’s natural circadian rhythms are out of whack.

And it turns out jetlag also affects the microbiota in your gut. In a study published in Cell, researchers from the Weizman Institute of Science, in Israel, found that in both humans and mice, the bacteria living in the gut were affected by changes in the biological clock. They did an experiment in which a group of volunteers travelled from the US to Israel, an eight to ten hour time difference. The poor mice in the study did not go anywhere, but researchers changed their feeding habits and the lights in their habitats to make them feel jetlagged.

Scientists took faecal samples before and after the travel (or mock travel) to see which bacteria were thriving in their guts, and they found that not only did the gut bacteria composition change, but also the microorganisms that prospered under the changing conditions were the ones most associated with obesity, and other health problems.

The researchers even transplanted stool from the jetlagged humans into mice without gut microbes and found those mice gained more weight and body fat and had higher blood sugar levels compared to mice that received stool from the individuals before being jetlagged.

If you take a flight once a year to go on your summer holidays, the fact that your gut microbiota change may not be a big deal, apart from the inconvenience of feeling dizzy for some days or having some intestinal discomfort. Because luckily the effects of jetlag on the composition of gut microbiota dissipate within a few weeks. But if you have to travel often, crossing the planet or changing time zones, or you are a shift worker or an airplane pilot, then you may have a problem, as alterations in gut microbiota composition are linked to obesity, diabetes and other health problems. This could be related to why frequent travellers often pack on extra pounds.

Jetlag is also associated with gastrointestinal problems, such as diarrhoea or constipation, due to the change of diet (enjoying the native food) and eating at different hours in order to adapt to the new time zone, although maybe they are more linked to fact of the travel than to the sleep disturbances due to jetlag.



Thaiss C, Zeevi D, Maayan L, et al. Transkingdom Control of Microbiota Diurnal Oscillations Promotes Metabolic Homeostasis. Cell. 2014; 159: 514-529.