Although only 16% of people in this study met the criteria for social jet lag, there were noticeable differences between the gut microbiomes of both groups. And those in the social jet lag group had a higher prevalence of three unfavorable microbial species. 

However, late nights are also often accompanied by other not-so-desirable habits. And those in the social jet lag group had a poorer diet quality (eating higher-calorie foods and less fiber, fruits, and vegetables). And surprisingly, eating nuts helped counter some of the negative changes to the gut microbiome. Information on alcohol intake was also collected, but even after it was accounted for, it didn’t change any of the study’s findings.

The study was not able to parse out whether the changes were directly tied to those dietary differences or other factors like sleep. Likely more studies will stem from this one to investigate how normalizing sleep patterns lead to (seemingly positive) changes in gut bacteria.