Grinding away at a job while everybody else sleeps can put your mental health at risk. According to new research, confining your dining to daytime hours might help reduce the odds of developing depression or anxiety.
When a normal internal body clock is disrupted, such as by being awake during typical sleeping hours, it can negatively impact an individual's mood and emotional well-being.
Studies suggest even after years spent on a roster of night shifts our body won't fully adapt to the altered schedule. In fact, the negative effects appear to be worse the longer a biological clock is thwarted.
So how can we protect shift workers like nurses, security guards, and fire fighters – who make up to 30 percent of the global workforce – from poor mental health while still maintaining crucial around-the-clock services?
Melatonin and light therapies are already being investigated as solutions. Now researchers are putting forward another potential panacea: altered meal timing.
"Our findings open the door for a novel sleep/circadian behavioral strategy that might also benefit individuals experiencing mental health disorders," says neuroscientist Sarah Chellappa, who helped conduct the randomized trial while working at Brigham and Women's Hospital in Boston.
"Our study adds to a growing body of evidence finding that strategies that optimize sleep and circadian rhythms may help promote mental health."
The typical human body's balance of hormones fluctuates throughout the day based on their circadian clock, and evidence suggests that nighttime meals can meddle with metabolism.
That could be part of the reason why shift workers tend to have a higher body mass index and a greater waist-to-hip ratio than daytime workers.
Impaired glycemic control is also a common risk factor for mood disruption. Moreover, depression and obesity often go hand in hand in a vicious cycle that elevates the risk and severity of either condition.
With these findings in mind, researchers are looking into whether avoiding meals at nighttime could improve the well-being of shift workers.
This is still an emerging area of research, but this recent trial suggests that confining meals to the daytime could help prevent mood vulnerabilities associated with night work.
Over the course of two weeks, 19 participants were subjected to simulated night work in a randomized, controlled trial.
Meals among one half of the group were eaten during both daytime and nighttime hours, while the other half only ate during the day.
Every other part of the trial was the same, including calories consumed, the duration of sleep, physical activity and lighting conditions.
When simulated night workers were served meals in the day and at night (as is common with many shift workers), the authors found a 26 percent increase in depression-like mood levels and a 16 percent increase in anxiety-like mood levels compared to a baseline measure. The group that only ate in the daytime reported no such mood changes.
Even more convincing is the fact that those individuals whose circadian rhythms showed the greatest degree of misalignment were also more likely to display depression- and anxiety-like symptoms.
"We found evidence that meal timing had moderate to large effects on depression-like and anxiety-like mood levels during simulated night work, and that such effects were associated with the degree of internal circadian misalignment," the authors write.
"These findings offer a proof-of-concept demonstration of an evidence-based meal timing intervention that may prevent mood vulnerability in shift work settings," they add.
The randomized trial was rigorously designed, albeit small in scope, but due to the experiment's design, the findings cannot tell us how or why the timing of a meal appears to have such a drastic effect on a shift worker's moods.
Further research is needed to explore whether glucose intolerance at nighttime could possibly play a role. Results from another recent randomized trial suggest that only eating during daytime hours can prevent glucose imbalances that shift workers otherwise develop.
There is also room for future studies to explore whether a misaligned circadian rhythm can change the gut microbiota in way that makes mental health worse.
Like the human hormonal system, the gut microbiome is also closely tied to the human circadian rhythm, and when a biological clock is misaligned, studies suggest the gut's microbiome can become disordered and promote inflammation.
What's more, an altered gut microbiome has been linked to symptoms of anxiety and depression.
"Meal timing is emerging as an important aspect of nutrition that may influence physical health," says Chellappa.
"But the causal role of the timing of food intake on mental health remains to be tested."
The study was published in PNAS.