Daytime-only eating may protect night shift workers from heart risks: study

By Stephen Beech

Eating only during the daytime could protect night shift workers from the increased risk of a heart attack or stroke, according to a new study.

Food timing could be a bigger risk factor than sleep timing when it comes to cardiovascular health, say scientists.

Several previous studies have shown that working night shifts is associated with serious health risks, including to the heart.

Now, new research suggests that eating only during the daytime could help people avoid the health risks associated with shift work.

Study senior author Professor Frank Scheer, of Brigham and Women’'s Hospital, in Boston, said: “Our prior research has shown that circadian misalignment - the mistiming of our behavioral cycle relative to our internal body clock – increases cardiovascular risk factors.

“We wanted to understand what can be done to lower this risk, and our new research suggests food timing could be that target.”

Animal studies have shown that aligning food timing with the internal body clock could reduce the health risks of staying awake during typical rest time, which prompted Prof Scheer and his colleagues to test the concept in humans.

For the new study, published in the journal Nature Communications, researchers enlisted 20 healthy young participants for a two-week in-patient study.

The participants had no access to windows, watches, or electronics that would clue their body clocks into the time.

The researchers explained that the effect of circadian misalignment could be determined by comparing how their body functions changed from before to after simulated night work.

Participants followed a “constant routine protocol” - a controlled laboratory set-up that can tease apart the effects of circadian rhythms from those of the environment and behavior patterns.

During the protocol, participants stayed awake for 32 hours in a dimly lit environment, maintaining constant body posture and eating identical snacks every hour.

After that, they participated in simulated night work and were assigned to either eat during the night time - as most night shift workers do - or only during the daytime.

The participants then followed another constant routine protocol to test the aftereffects of the simulated night work.

Both groups had an identical schedule of naps, so any differences between the groups were not due to differences in sleep schedule.

The research team examined the aftereffects of the food timing on the participants’ cardiovascular risk factors and how they changed after the simulated night work.

Researchers measured several cardiovascular risk factors, including autonomic nervous system markers, plasminogen activator inhibitor-1 which increases the risk of blood clots, and blood pressure.

They found that the cardiovascular risk factors increased after simulated night work compared to the baseline in the participants who were scheduled to eat during the day and night.

However, the risk factors stayed the same in the study participants who only ate during the daytime, even though how much and what they ate was not different between the groups - only when they ate.

Study lead author Professor Sarah Chellappa, of the University of Southampton, added: "Our study controlled for every factor that you could imagine that could affect the results, so we can say that it’s the food timing effect that is driving these changes in the cardiovascular risk factors.”

While further research is necessary to show the long-term health effects of daytime compared to night-time eating, the team described the results as “promising” and suggested that people could improve their health by adjusting food timing.

Chellappa added that avoiding or limiting eating during night-time hours may benefit night workers, those who experience insomnia or sleep-wake disorders, people with variable sleep/wake cycles, and those who often travel across time zones.