Social jet lag, the shift that one’s internal body clock takes when sleeping patterns change between workdays and free days, might cause unfavorable changes in the gut microbiome, according to a new observational study published in the European Journal of Nutrition, by causing a number of unfavorable species to flourish. The study was conducted by King’s College London and ZOE, a personalized nutrition company.
 
Previous research has linked working shifts and disruptions in circadian rhythm to increased risks of weight gain, heart problems, and diabetes. There is less awareness about smaller sleep inconsistencies, such as waking early with an alarm clock on workdays rather than waking up naturally.
 
“We know that major disruptions in sleep, such as shift work, can have a profound impact on your health,” said senior author Dr. Wendy Hall. “This is the first study to show that even small differences in sleep timings across the week seems to be linked to differences in gut bacterial species. Some of these associations were linked to dietary differences but our data also indicates that other, as yet unknown, factors may be involved. We need intervention trials to find out whether improving sleep time consistency can lead to beneficial changes in the gut microbiome and related health outcomes.”
 
These changes happened alongside shifts in diet quality, habits, and inflammation, in a cohort of 934 people. Researchers assessed blood, stool, and gut microbiome samples as well as glucose measurements, and tracked correlations to both regular and irregular sleeping patterns. The cohort of individuals were mainly lean and healthy, and got more than seven hours of sleep nightly on average.
 
Just a 90-minute difference in the timing of the midpoint of sleep (the halfway point between sleep time and wake-up time) was linked to significant changes in the abundance of specific bacteria species.
 
Three of six microbiota species which were significantly more abundant in the social jet lag group had associations with poor diet quality, indicators of obesity and cardiometabolic health issues, and higher levels of inflammation and cardiovascular risk, according to the authors. These three species were Clostridia bacterium SGB14263, Clostridia bacterium SGB3940, and Peptococcaceae bacterium GB49168.
 
Further, diet quality index was poorer in the social jet lag group, with lower intakes of fruits and nuts and higher intakes of sugar-sweetened beverages.
 
“Sleep is a key pillar of health, and this research is particularly timely given the growing interest in circadian rhythms and the gut microbiome,” said Kate Bermingham, PhD, from King’s College London and senior nutrition scientist at ZOE. “Even a 90-minute difference in the mid-point of sleep can encourage microbiota species which have unfavorable associations with your health.”