Daytime eating shields night shift workers from heart risks

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Apr 14 2025

A new study reveals that confining meals to daytime hours can help preserve cardiovascular function and reduce disease risk in night shift workers, underscoring the power of meal timing in mitigating circadian disruption.

Study: Daytime eating during simulated night work mitigates changes in cardiovascular risk factors: secondary analyses of a randomized controlled trial. Image Credit: Shutterstock AI Generator / Shutterstock.com

A recent study published in Nature Communications examines how daytime eating may preserve cardiovascular health among night shift workers.

Altered diet habits during shift work

About 15% of workers in residing developed nations perform night shift work, which increases the risk of developing cardiovascular disease (CVD). Circadian misalignment, which occurs due to disturbances between the central circadian pacemaker and normal sleep/wake cycles, likely contributes to dysfunctional cardiometabolic health in shift workers.

Circadian organization is fundamental for normal health and longevity, while circadian disruption is implicated in the etiology of cardiac disease.”

The relationship between shift work and cardiovascular health is multifactorial, with several studies suggesting that meal timing may contribute to the increased risk of CVD among shift workers. To elucidate the role of meal timing in this risk, the researchers of the current study compared the effects of eating during the day and night to only eating during daytime hours in a cohort of study participants exposed to simulated night work.

About the study

The researchers of the current study conducted a single-blinded trial comprising seven females and 12 males. To simulate night work, the Forced Desynchrony protocol was utilized, which involved exposing the study participants to a total of four 28-hour days.

During each 28-hour cycle, all meals in the Nighttime Meal Control (NMC) group were consumed during the day and at night, which is a common practice among shift workers.

The remaining study participants were placed in the Daytime Meal Intervention (DMI) group, which involved a modified 28-hour FD protocol. All meals in the DMI group were consumed during the daytime.

Cardiac vagal regulation was assessed by the percentage of successive normal cardiac interbeat intervals greater than 50 milliseconds (pNN50), root mean square of successive differences (RMMSD), which is a marker of heart rate variability, and low/high cardiac frequency (LF/HF). The levels of circulating plasminogen activator inhibitor-1 (PAI-1), which a prothrombotic factor involved in circadian rhythm, were also measured, in addition to heart rate and blood cortisol levels.

Cardiovascular measurements were assessed during Constant Routine (CR) protocols, which minimizes the potential effects of behavior and the environment on physiological parameters.

Daytime eating preserves heart function

Following exposure to simulated night work, pNN50 and RMSSD levels declined by 25.7% and 14.3%, respectively, in the NMC group as compared to baseline levels. These changes were not observed in the DMI group.

Simulated night work also led to a significant increase in LF/HF ratio levels of 5.5%, whereas no change was observed in the DMI group. PAI-1 levels rose by 23.9% in the NMC group after simulated nightwork, whereas DMI study participants did not exhibit any significance change in PAI-1 levels.

No significant changes in cortisol levels or heart rate were observed in the NMC and DMI groups. However, blood pressure levels were reduced by 6-8% in the DMI group following exposure to simulated night work.

Implications

By restricting eating to only daytime hours, the study findings demonstrate that meal timing, rather than simulated night shift, has a more significant impact on cardiovascular health than night work alone. More specifically, eating during both nighttime and daytime hours, rather than daytime alone, led to reduced cardiac vagal modulation, which has been consistently reported in previous clinical trials.

Daytime meal timing avoids the adverse effects of simulated nighwork on cardiovascular function in humans.”

Night shift workers often eat their meals during nighttime hours, skip other meals during the day, and frequently snack. The study findings confirm the importance of meal timing in mitigating the risk of cardiovascular disease among night shift workers and suggest that meal-timing based behavioral interventions may improve health outcomes in this population.

Nevertheless, future studies with larger sample sizes and real-life shift work conditions, including rotating or irregular work routines, are needed to validate and extend these findings.