Study reveals harmful gut bacteria linked to irregular sleep patterns

A recent peer-reviewed publication by researchers from King’s College London and ZOE, the personalised nutrition company, has shed light on the connection between irregular sleep patterns and harmful bacteria in the gut. Published in The European Journal of Nutrition, this study is the first to identify multiple associations between “social jet lag” – the disruption of the internal body clock due to inconsistent sleep patterns – and various factors like diet quality, eating habits, inflammation, and gut microbiome composition within a single cohort.

Prior research has already demonstrated that working shifts can disturb the body’s natural rhythm, leading to increased risks of weight gain, heart problems, and diabetes. However, this study highlights the lesser-known impact of minor inconsistencies in sleep patterns, such as waking up early with an alarm clock on workdays versus waking naturally on non-workdays.

Dr Wendy Hall, the senior author from King’s College London, emphasised, “Even small differences in sleep timings across the week seem to be linked to differences in gut bacterial species. While some associations were tied to dietary differences, our data also suggests the involvement of other, yet unidentified, factors. Intervention trials are needed to determine whether improving sleep time consistency can positively impact the gut microbiome and related health outcomes.”

The gut microbiome, the composition of microbes in the digestive system, plays a crucial role in affecting an individual’s health by producing either harmful toxins or beneficial metabolites. Specific microbial species can also influence a person’s risk of developing long-term health conditions like diabetes, heart disease, and obesity. The diversity of the gut microbiome can be influenced by the food one consumes.

The study analysed 934 individuals from the ZOE PREDICT study, the largest ongoing nutritional study of its kind. The participants with irregular sleep schedules were compared to those with regular sleep patterns. Unlike previous studies focusing on populations with obesity or diabetes, this cohort primarily consisted of lean and healthy individuals who typically got more than seven hours of sleep per night throughout the week.

The findings revealed that even a mere 90-minute difference in the midpoint of sleep, the halfway point between sleep time and wake-up time, was associated with variations in gut microbiome composition.

People with social jet lag tended to have lower overall diet quality, consumed more sugar-sweetened beverages, and had lower intakes of fruits and nuts, factors that directly influenced the abundance of specific gut microbiota.

Among the six microbiota species found to be more abundant in the social jet lag group, three were linked to “unfavourable” health outcomes. These microbes were associated with poor diet quality, indicators of obesity and cardiometabolic health, and markers of higher inflammation and cardiovascular risk in the blood.

Kate Bermingham, PhD, the first author from King’s College London and senior nutrition scientist at ZOE, commented, “Sleep is a key pillar of health, and this research is particularly timely given the growing interest in circadian rhythms and the gut microbiome. Even a 90-minute difference in the midpoint of sleep can encourage microbiota species which have unfavourable associations with your health.”