Researchers devised a trial that replicated night work and then compared the impact of daytime and midnight eating with simply daytime eating. The researchers discovered that among individuals in the daytime and nighttime eating groups, depression-like mood levels increased by 26% and anxiety-like mood levels increased by 16%. This rise was not observed in the daytime-only eating group, suggesting that meal timing may alter mood sensitivity.
“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-corresponding author Frank A. J. L. Scheer, PhD, Director of the Medical Chronobiology Program in the Brigham’s Division of Sleep and Circadian Disorders. “Future studies in shift workers and clinical populations are required to firmly establish if changes in meal timing can prevent their increased mood vulnerability. Until then, our study brings a new ‘player’ to the table: the timing of food intake matters for our mood.”
Shift workers account for up to 20 per cent of the workforce in industrial societies and are directly responsible for many hospital services, factory work, and other essential services. Shift workers often experience a misalignment between their central circadian clock in the brain and daily behaviours, such as sleep/wake and fasting/eating cycles. Importantly, they also have a 25 to 40 per cent higher risk of depression and anxiety.
“Shift workers — as well as individuals experiencing circadian disruption, including jet lag — may benefit from our meal timing intervention,” said co-corresponding author Sarah L. Chellappa, MD, PhD, who completed work on this project while at the Brigham. Chellappa is now in the Department of Nuclear Medicine, University of Cologne, Germany. “Our findings open the door for a novel sleep/circadian behavioural strategy that might also benefit individuals experiencing mental health disorders. Our study adds to a growing body of evidence finding that strategies that optimize sleep and circadian rhythms may help promote mental health.”
To conduct the study, Scheer, Chellappa, and colleagues enrolled 19 participants (12 men and 7 women) for a randomized controlled study. Participants underwent a Forced Desynchrony protocol in dim light for four 28-hour “days,” such that by the fourth “day” their behavioural cycles were inverted by 12 hours, simulating night work and causing circadian misalignment.
Participants were randomly assigned to one of two meal timing groups: the Daytime and Nighttime Meal Control Group, which had meals according to a 28-hour cycle (resulting in eating both during the night and day, which is typical among night workers), and the Daytime-Only Meal Intervention Group, which had meals on a 24-hour cycle (resulting in eating only during the day). The team assessed depression- and anxiety-like mood levels every hour.
The researchers discovered that meal time had a substantial impact on the mood levels of the subjects. When compared to baseline, participants in the Daytime and Nighttime Meal Control Groups reported higher depression-like and anxiety-like mood levels throughout the simulated night shift (day 4). (day 1). During the simulated night shift, there were no changes in mood in the Daytime Meal Intervention Group. Participants with higher levels of circadian misalignment reported increased despair and anxiety-like symptoms.
“Meal timing is emerging as an important aspect of nutrition that may influence physical health,” said Chellappa. “But the causal role of the timing of food intake on mental health remains to be tested. Future studies are required to establish if changes in meal timing can help individuals experiencing depressive and anxiety/anxiety-related disorders.”