• The researchers simulated night work conditions on study participants
  • Those who ate both at night and daytime had increased depression-like mood
  • Meal timings is an "emerging aspect of nutrition," the researchers said

People may not think that the time of day in which they eat can affect their mental health. But for shift workers and others who experience circadian disruptions, this can spell the difference between having increased mental health woes or not, a new study has found.

Mental health disorders have a major impact on society, with "lost workforce productivity alone" having an estimated global cost of $1 trillion, according to the researchers of a new study published Monday in the Proceedings of the National Academy of Sciences.

Among workers, shift workers are particularly hard hit by mental health woes, having a whopping 25 to 40% higher risk of depression and anxiety. This, researchers say, is in part due to "misalignments" in their circadian rhythms and daily environments.

For their work, the researchers conducted their study on 19 participants, 12 of whom were women while seven were men. They were subjected to a 14-day clinical trial that placed them in simulated night work conditions.

Some of them had meals both in nighttime and daytime (daytime and nighttime meal control [DNMC] group), which is said to be common among shift workers, according to the Brigham and Women's Hospital news release. The others were placed in the daytime-only meal intervention (DMI) group, wherein they ate only during the day. The researchers then assessed their depression and anxiety-like symptoms each hour.

"Daytime eating — despite mistimed sleep — can maintain internal circadian alignment and prevent glucose intolerance during simulated night work," the researchers wrote. "As impaired glycemic control is a risk factor for mood disruption, we tested the prediction that daytime eating prevents mood vulnerability, despite simulated night work."

Indeed, they found that those who ate both during the day and night had 26.2% increased depression-like mood levels and 16.1% anxiety-like mood levels. On the other hand, the group that ate only in the daytime did not see such increases.

"These effects were unlikely due to differences in study design, as the laboratory protocol of both groups was identical (i.e., caloric/macronutrient intake, physical activity, posture, sleep duration, lighting conditions), except for the timing of meals," the researchers noted.

This shows how crucial diet is in one's mental health, the researchers said, citing a previous study on more than 500,000 individuals who found that those with unhealthy diets had worse sleep and "mental health symptomatology." Meal timing, according to them, is an "emerging aspect of nutrition" that may be studied further.

"Shift workers — as well as individuals experiencing circadian disruption, including jet lag — may benefit from our meal timing intervention," study co-corresponding author Sarah L. Chellappa, now of the University of Cologne, Germany, said in the news release.

"Future studies in shift workers and clinical populations are required to firmly establish if changes in meal timing can prevent their increased mood vulnerability," study co-corresponding author Frank A. J. L. Sheer of Brigham's Division of Sleep and Circadian Disorders added. "Until then, our study brings a new 'player' to the table: the timing of food intake matters for our mood."

Meal, Food, Breakfast, watch, clock
Representation. Rolf van de Wal/Pixabay