Researchers created a simulated shift-work schedule and found increases in depression and anxiety for those eating at odd hours.
"Our findings provide evidence for the timing of food intake as a novel strategy to potentially minimize mood vulnerability in individuals experiencing circadian misalignment, such as people engaged in shift work, experiencing jet lag, or suffering from circadian rhythm disorders," said co-author Frank Scheer. He's director of the medical chronobiology program in Brigham and Women's Hospital's Division of Sleep and Circadian Disorders in Boston.
"Future studies in shift workers and clinical populations are required to firmly establish if changes in meal timing can prevent their increased mood vulnerability," Scheer said in a hospital news release. "Until then, our study brings a new 'player' to the table: the timing of food intake matters for our mood."
About 20% of the workforce in industrial societies does shift work in places like factories and hospitals. These workers often experience a misalignment between their central "circadian clock" in the brain and daily behaviors, including sleep/wake and fasting/eating cycles, according to the study. They also have about a 25% to 40% higher risk of depression and anxiety.
The study enrolled 12 men and seven women in a randomized, controlled study. Participants underwent a "forced desynchrony" protocol in dim light for four 28-hour "days" instead of 24-hour days.
By the fourth "day," their behavioral cycles were inverted by 12 hours, which simulated night work and caused circadian misalignment, researchers said.
Participants were then randomly assigned to one of two meal timing groups. In the control group, meals were eaten on a 28-hour cycle, which meant folks were eating both during the night and day. This is a typical schedule for night workers.
In the daytime-only meal intervention group, participants ate meals on a 24-hour cycle, which meant they were eating only during the day.
While this was ongoing, the research team assessed mood levels every hour.
By day 4, for those in the daytime/nighttime meal group, their depression-like mood levels had increased by 26% and anxiety-like mood levels by 16%.
The daytime-only group had no mood changes.
The participants with a greater degree of circadian misalignment experienced more mood changes, the authors said.
"Shift workers -- as well as individuals experiencing circadian disruption, including jet lag -- may benefit from our meal timing intervention," said co-author Dr. Sarah Chellappa, who worked at Brigham at the time of the study. She is now at the University of Cologne in Germany.
"Our findings open the door for a novel sleep/circadian behavioral strategy that might also benefit individuals experiencing mental health disorders," Chellappa said in the release. "Our study adds to a growing body of evidence finding that strategies that optimize sleep and circadian rhythms may help promote mental health."
Further studies will be needed to establish if changes in meal timing can help people with depressive- and anxiety-related disorders, she said.
The findings were published Sept. 12 in the Proceedings of the National Academy of Sciences.
The U.S. Department of Labor has more on the impact of extended or irregular shifts at work.
SOURCE: Mass General Brigham, news release, Sept. 12, 2022