Firefighters working 24-hour shifts who ate only between 9am and 7pm saw improvements in heart health, blood sugar and blood pressure
October 4, 2022
Eating within the same 10-hour time frame per day can counteract the health effects of shift work, such as increased risk of diabetes, cardiovascular disease and cancer.
Shift work disrupts circadian rhythms, the 24-hour sleep-wake cycles that also govern the activity of various organs. Nutrition can regulate these rhythms. To see if changing what and when people eat could counteract the harms of shift work, Satchidananda Panda of the Salk Institute for Biological Studies in California and colleagues studied firefighters working 24-hour shifts.
They advised 137 firefighters in San Diego, California, to follow a Mediterranean diet — high in fruits, vegetables, legumes, whole grains and olive oil and low in red meat and sugar — for 12 weeks. They asked 70 to eat in the same 10-hour time frame every day, and the other 67 to eat whenever they wanted. Before the study, the groups had no significant differences in health, and more than 70 percent of the participants had at least one risk factor for heart or metabolic disease, such as high blood pressure or obesity.
Participants recorded when they ate using a smartphone app and answered surveys about sleep and well-being before and after the study. The researchers also collected blood samples and tracked the participants’ weight. Firefighters in the time-restricted feeding group saw greater improvements in health after 12 weeks compared to the control group. The biggest improvement was in the size of harmful cholesterol particles known as very low-density lipoproteins, which increase the risk of heart disease. On average, the size of these particles decreased by nearly 3% in the time-restricted feeding group compared to a 0.5% reduction in the control group.
“This is very important because the leading cause of death or disability for firefighters is cardiovascular disease,” says Panda.
Firefighters on the time-restricted diet also had, on average, slightly greater reductions in weight, diastolic blood pressure, alcohol consumption, caloric intake, and sleep disturbances. The time-restricted diet also led to greater drops in blood pressure and blood sugar among firefighters with elevated levels of those markers to begin with.
“If firefighters eat a Mediterranean diet, that’s good, but if they combine the diet with time-restricted eating, that’s even better,” Panda says. Nutrition helps determine when organs perform certain functions. The stomach, for example, normally digests food during the day and recovers at night, but it cannot perform these functions simultaneously. A consistent meal schedule throughout the day reinforces this pattern and ensures that different organs have time to recover, he says.
A time-restricted diet may also help prevent health problems associated with shift work, as previous research has shown it reduced rates of diseases such as diabetes in mice that had disrupted circadian rhythms and an increased risk of obesity and diabetes.
However, it’s not clear from the current study whether the diet is feasible in the long term, says Jingyi Qian of Harvard University in Massachusetts. “If we want to have sustained benefits for shift workers, we need to know if they can stick with this intervention for a year or even longer,” she says.
Journal reference: Cellular metabolismDOI: 10.1016/j.cmet.2022.08.018
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