Batya Swift Yasgur, MA, LSW
September 26, 2022
Shift workers who confine their eating to the daytime may experience fewer mood symptoms compared to those who eat both day and night, new research suggests.
Investigators at Brigham and Women’s Hospital, Boston, Massachusetts, created a simulated nightwork schedule for 19 individuals in a laboratory setting. Participants then engaged in two different meal timing models ― daytime-only meals (DMI), and meals taken during both daytime and nighttime (DNMC).
Depression- and anxiety-like mood levels increased by 26% and 16%, respectively, among the daytime and nighttime eaters, but there was no such increase in daytime-only eaters.
“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,” co-corresponding author Frank A. J. L. Scheer, PhD, director of the Medical Chronobiology Program, Brigham and Women’s Hospital, Massachusetts, said in a news release.
The study was published online September 12 in the Proceedings of the National Academy of Sciences.
Misaligned Circadian Clock
“Shift workers often experience a misalignment between their central circadian clock in the brain and daily behaviors, such as sleep/wake and fasting/eating cycles,” senior author Sarah Chellappa, MD, PhD, currently the Alexander Von Humboldt Experienced Fellow in the Department of Nuclear Medicine, University of Cologne, Germany. Chellappa was a postdoctoral fellow at Brigham and Women’s Hospital when the study was conducted.
“They also have a 25% to 40% higher risk of depression and anxiety,” she continued. “Since meal timing is important for physical health and diet is important for mood, we sought to find out whether meal timing can benefit mental health as well.”
Given that impaired glycemic control is a “risk factor for mood disruption,” the researchers tested the prediction that daytime eating “would prevent mood vulnerability, despite simulated night work.”
To investigate the question, they conducted a parallel-design, randomized clinical trial that included a 14-day circadian laboratory protocol with 19 healthy adults (12 men, seven women; mean age, 26.5 ± 4.1 years) who underwent a forced desynchrony (FD) in dim light for 4 “days,” each of which consisted of 28 hours. Each 28-hour “day” resulted in an additional 4-hour misalignment between the central circadian clock and external behavioral/environmental cycles.
By the fourth day, the participants were misaligned by 12 hours, compared to baseline (ie, the first day). They were then randomly assigned to two groups.
The DNMC group — the control group — had a “typical 28-hour FD protocol,” with behavioral and environmental cycles (sleep/wake, rest/activity, supine/upright posture, dark during scheduled sleep/dim light during wakefulness) scheduled on a 28-hour cycle. Thus, they took their meals during both “daytime” and “nighttime,” which is the typical way that night workers eat.
The DMI group underwent a modified 28-hour FD protocol, with all cycles scheduled on a 28-hour basis, except for the fasting/eating cycle, which was scheduled on a 24-hour basis, resulting in meals consumed only during the “daytime.”
Depression- and anxiety-like mood (which “correspond to an amalgam of mood states typically observed in depression and anxiety) were assessed every hour during the 4 FD days, using computerized visual analogue scales.
Nutritional Psychiatry
Participants in the DNMC group experienced an increase from baseline in depression- and anxiety-like mood levels of 26.2% (95% CI, 21 – 31.5; P = .001; P value using false discovery rate [PFDR] = .01; effect-size r = .78) and 16.1% (95% CI, 8.5 – 23.6; P = .005; PFDR = .001; effect-size r = .47), respectively.
By contrast, a similar increase did not take place in the DMI group for either depression- or anxiety-like mood levels (95% CI, -5.7% to 7.4%, P not significant; and 95% CI, -3.1% to 9.9%, P not significant, respectively).
The researchers tested “whether increase mood vulnerability during simulated night work was associated with the degree of internal circadian misalignment” — defined as “change in the phase difference between the acrophase of circadian glucose rhythms and the bathyphase of circadian body temperature rhythms.”
They found that a larger degree of internal circadian misalignment was “robustly associated” with more depression-like (r = .77; P = .001) and anxiety-like (r = .67; P = .002) mood levels during simulated night work.
The findings imply that meal timing had “moderate to large effects in depression-like and anxiety-like mood levels during night work, and that such effects were associated with the degree of internal circadian misalignment,” the authors write.
The laboratory protocol of both groups was identical except for the timing of meals, they emphasize. They note that the “relevance of diet on sleep, circadian rhythms, and mental health is receiving growing awareness with the emergence of a new field, nutritional psychiatry.”
People who experience depression “often report poor-quality diets with high carbohydrate intake,” and there is evidence that adherence to the Mediterranean diet is associated “with lower odds of depression, anxiety, and psychological distress.”
They caution that although these emerging studies suggest an association between dietary factors and mental health, “experimental studies in individuals with depression and/or anxiety/anxiety-related disorders are required to determine causality and direction of effects.”
They describe meal timing as “an emerging aspect of nutrition, with increasing research interest because of its influence on physical health.” However, they note, “the causal role of the timing of food intake on mental health remains to be tested.”
Novel Findings
Commenting for Medscape Medical News, Kathleen Merikangas, PhD, distinguished investigator and chief, Genetic Epidemiology Research Branch, Intramural Research Program, National Institute of Mental Health, Bethesda, Maryland, described the research as important with novel findings.
The research “employs the elegant, carefully controlled laboratory procedures that have unraveled the influence of light and other environmental cues on sleep and circadian rhythms over the past two decades,” said Merikangas, who was not involved with the study.
“One of the most significant contributions of this work is its demonstration of the importance of investigating circadian rhythms of multiple systems rather than solely focusing on sleep, eating, or emotional states that have often been studied in isolation,” she pointed out.
“Growing evidence from basic research highlights the interdependence of multiple human systems that should be built into interventions that tend to focus on one or two domains.”
She recommends that this work be replicated “in more diverse samples…in both controlled and naturalistic settings…to test both the generalizability and mechanism of these intriguing findings.”
The study was funded by the National Institutes of Health. Individual investigators were funded by the Alexander Von Humboldt Foundation and the American Diabetes Association. Chellapa has disclosed no relevant financial relationships. The other authors’ financial relationships are listed in the original article. Merikangas has disclosed no relevant financial relationships.
Proc Natl Acad Sci. Published online September 12, 2022.
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