Research highlights shift workers meal times affect mood (guest blog)

By Sarah L. Chellappa and Frank A.J.L. Scheer

Shift workers account for up to 20 percent of the workforce in industrial societies and are directly responsible for many hospital services, factory work, and other essential services. Shift workers often experience circadian misalignment, the 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 percent higher risk of anxiety. 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.

We enrolled 19 participants (12 men and 7 women) in a laboratory study that included four 28-hour “days,” such that by the fourth “day” their behavioral cycles were inverted by 12 hours, thus simulating night work and causing circadian misalignment. Participants were randomized to either a Daytime & Nighttime Meal Control Group, which had meals according to a 28-hour cycle (resulting in eating during the night and day, as night workers often eat), or a Daytime-only Meal Intervention Group, which had meals on a 24-hour cycle (resulting in eating only during the day). We found that during the simulated night shift (day 4), those in the Daytime and Nighttime Meal Control Group had more depression-like and anxiety-like mood levels, compared to baseline (day 1). However, no such worsening of mood levels happened during the simulated night work in the Daytime-only Meal Intervention Group. Furthermore, those who had a greater degree of internal circadian misalignment, the misalignment between endogenous circadian rhythms in the body, experienced more depression- and anxiety-like mood.

What would be the potential mechanisms underlying the association between the time of day of eating and mental health? We previously showed in the same laboratory experiment that participants in the Daytime and Nighttime Meal Control Group had impaired glucose tolerance (a risk factor for type 2 diabetes) during the simulated night shift. Conversely, no such changes happened during the simulated night work in the Daytime-only Meal Intervention Group. Because high glucose levels are associated with depression, the beneficial effects of daytime eating on glucose tolerance may extend to mood perception.

Our findings suggest that meal timing is important for mood. Of note, our study aimed at answering fundamental research questions; hence, we used a stringently controlled 14-day laboratory protocol. Because of that, it is challenging to make a direct translation of our daytime meal intervention to meal schedules in real-life shift workers or patient populations. Future research is needed to establish if meal timing interventions can prevent depressed and anxious mood states in shift workers. Until such approaches are implemented, it may be helpful if night workers reconsidered the amount of calories, and especially carbohydrates, consumed in the nighttime.

The full paper can be read here: https://www.pnas.org/doi/abs/10.1073/pnas.2206348119?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub++0pubmed

Sarah L. Chellappa is Alexander Von Humboldt Experienced Fellow, Department of Nuclear Medicine, University of Cologne, Germany.

Frank A.J.L. Scheer, Ph.D. is Professor of Medicine, Harvard Medical School (HMS), Director, Medical Chronobiology Program, Brigham and Women’s Hospital (BWH) and Senior Investigator (Senior Neuroscientist), Departments of Medicine and Neurology, BWH

To access our ‘Nutrition and Anxiety – a self-help guide’ where the various components of a healthy diet in relation to stress are examined, please see here.

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