# Gut Microbiota Diversity and Composition Across Shift Types and the Effects of Walnut Supplementation—An Observational and Interventional Study

## TL;DR

This study finds that night shifts may temporarily reduce gut microbiota diversity, but walnut supplementation and healthier diets can help preserve it in shift workers.

## Contribution

The study demonstrates that walnut supplementation may mitigate gut microbiota diversity loss during night shifts, using a within-person design.

## Key findings

- Night shifts transiently reduced gut microbiota diversity during observation but not with walnut supplementation.
- Healthier dietary patterns were consistently linked to greater gut microbiota diversity.
- Gut microbiota composition remained largely stable across shift types and interventions.

## Abstract

Public Health Relevance—how does this work relate to a public health issue?
Shift work is a widespread occupational exposure associated with circadian disruption and increased risk of chronic metabolic diseases.Alterations in gut microbiota diversity may represent a biological pathway linking night shift work, diet quality, and long-term health outcomes.

Shift work is a widespread occupational exposure associated with circadian disruption and increased risk of chronic metabolic diseases.

Alterations in gut microbiota diversity may represent a biological pathway linking night shift work, diet quality, and long-term health outcomes.

Public Health Significance—why is this work of significance to public health?
Using a within-person design, this study shows that overall gut microbiota composition remains largely stable across shift types, while night shifts may transiently reduce microbial diversity.Healthier dietary patterns were consistently associated with greater gut microbiota diversity, and walnut supplementation appeared to attenuate diversity loss during night shifts.

Using a within-person design, this study shows that overall gut microbiota composition remains largely stable across shift types, while night shifts may transiently reduce microbial diversity.

Healthier dietary patterns were consistently associated with greater gut microbiota diversity, and walnut supplementation appeared to attenuate diversity loss during night shifts.

Public Health Implications—what are the key implications or messages for practitioners, policy makers and/or researchers in public health?
Targeted nutritional strategies focusing on overall diet quality may help preserve gut microbiota diversity in shift-working populations.These findings support further public health research on dietary and timing-based interventions to mitigate the health effects of circadian disruption in shift workers.

Targeted nutritional strategies focusing on overall diet quality may help preserve gut microbiota diversity in shift-working populations.

These findings support further public health research on dietary and timing-based interventions to mitigate the health effects of circadian disruption in shift workers.

Shift workers are at elevated risk of chronic diseases due to circadian rhythm disruption, suboptimal lifestyle behaviors, and potentially altered gut microbiota (GM). This study investigated variations in GM diversity and composition across three weekly shifts in rotating shift workers and following walnut supplementation. Using a within-person design, GM diversity and composition were compared in 13 shift workers during morning, afternoon, and night shifts. After a three-week observational period, participants added a daily serving of walnuts to their habitual diet for an additional three weeks. GM was analyzed via 16S rRNA sequencing, assessing diversity and bacterial composition across shift types and between the observational and interventional phases. Overall GM composition did not differ between the beginning and end of shifts, by shift type, or following walnut supplementation. Bacterial diversity remained stable except for a significant decrease at the end of the night shift during observation (p = 0.03), which was not observed during walnut supplementation. GM clustered strongly by subject, and a healthier diet correlated with greater mean GM diversity (r = 0.64, p = 0.02). Despite overall GM stability, the decline in diversity during night shifts suggests that targeted nutritional strategies, such as walnut supplementation, may help preserve gut health in shift workers.