Working overnight shifts has long been associated with a higher risk of heart disease. Now, a large observational study suggests that fiber intake may influence how that risk plays out.
Researchers from Uppsala University analyzed data from more than 220,000 adults in the UK Biobank and followed participants for about 12 years. The findings were published in the European Journal of Epidemiology.
Before diving into the results, it is worth noting the study’s funding. The research was supported by the Novo Nordisk Foundation, the Department of Pharmaceutical Biosciences at Uppsala University, the Åke Wiberg Foundation and the Diabetes Foundation. The authors state that funders had no role in the study design, analysis or publication decisions. Open access funding was provided by Uppsala University.
Participants were grouped as day workers, occasional night shift workers and regular night shift workers. All had completed detailed dietary questionnaires between 2006 and 2010. Researchers then tracked new cases of coronary artery disease over time.
Regular night shift workers who reported lower fiber intake had a higher risk of coronary artery disease compared with those who consumed more fiber.
“A moderate intake of about 19 grams of fiber per day was linked to a lower risk for those who worked night shifts regularly,” said Diana Nôga, the study’s lead author. “For those who worked night shifts sporadically, about 15 grams was enough. The current recommendation for adults is about 25 grams of dietary fiber per day.”
The amounts observed in the study are not new dietary recommendations. Instead, they reflect intake levels within this cohort that were associated with relatively lower risk. Notably, even the higher intake levels reported among night workers were still below the general recommendation of about 25 grams per day for adults.
Researchers adjusted for a range of lifestyle factors, including smoking, physical activity and other aspects of diet. While observational research cannot prove cause and effect, the association between higher fiber intake and lower coronary risk remained after these adjustments.
“The link between fibre and a lower risk of heart disease is not just because those who eat more fibre generally have a healthier lifestyle,” said Christian Benedict, senior author of the study. “We know this because we adjusted for various lifestyle factors in the analysis.”
He added that one possible explanation is that fiber may influence gut bacteria and blood lipid levels in ways that are particularly relevant for people whose sleep and eating schedules are misaligned with their internal clocks.
Shift work disrupts circadian rhythms, which regulate metabolism, hormone release and cardiovascular function. Over time, that disruption has been associated with higher rates of obesity, type 2 diabetes and coronary artery disease. Diet may be one of several factors that can either compound or help buffer that risk.
Fiber-rich foods include whole grains, vegetables, fruits, legumes and lentils. The researchers emphasize that dietary changes should complement, not replace, other heart-protective behaviors such as not smoking, staying physically active and getting adequate sleep when possible.
As with most nutrition research based on self-reported food intake, measurement error and residual confounding are possible. The UK Biobank population also does not perfectly represent all demographic groups. Still, the large sample size and long follow-up strengthen the findings.
For people who regularly work nights, the study suggests that fiber intake may be one dietary factor worth paying attention to. It does not mean fiber cancels out the health risks of circadian disruption. But it does reinforce a broader pattern seen in many populations: dietary fiber remains consistently linked with better cardiovascular outcomes.
This study was supported by the Novo Nordisk Foundation, the Department of Pharmaceutical Biosciences at Uppsala University, the Åke Wiberg Foundation and the Diabetes Foundation. Open access funding was provided by Uppsala University.