A large long-term study suggests that what shift workers eat, especially how much fiber they consume, could meaningfully influence their risk of coronary heart disease, offering a potential dietary strategy to counter the cardiovascular strain of working through the night.
Study: Night shift work, dietary patterns, and coronary heart disease. Image credit: Jacob Lund/Shutterstock.com
CHD risk is higher among shift workers than among daytime workers. A recent paper in the journal European Journal of Epidemiology examines this difference in association with fiber intake and meat avoidance to identify a possible mediatory role.
Why shift workers face higher CHD risk
Night shift work is essential in multiple occupations, including firefighting, healthcare, and law enforcement. However, it interrupts biological sleep-wake cycles. Impaired sleep prevents the associated repair and recovery benefits for the body’s normal functioning.
The cardiovascular system is among the most sensitive to such disruptions, and regular night shift work is correlated with a higher risk of cardiovascular disease (CVD), especially CHD. To protect against this, the AHA compiled a list of cardiovascular health components, called Life’s Essential 8.
Avoiding meat and increasing dietary fiber intake appear to be effective for preventing CVD. The increased risk of CHD in night shift workers has not been specifically examined for association with these dietary factors, despite their potential for dietary guidelines in this subgroup of the population.
Comparing daytime, occasional, and night shifts
The study involved 222,801 participants, with a mean age of ~53 years. They were categorized as:
- Daytime workers (83.6 %)
- Shift workers, but with few or no night shifts (13 %)
- Night shift workers (3.3 %)
A dietary questionnaire was used to assess dietary habits. Cardiovascular events were recorded over a median follow-up of 12.6 years.
Higher fiber intake attenuates shift-related risk
The results show that the CHD hazard was 10 % higher among night shift workers compared to daytime workers. Shift workers with few or no night shifts did not differ significantly from daytime workers after full adjustment for sociodemographic and lifestyle factors.
Irrespective of night shifts, shift workers had a higher CHD risk associated with lower daily fiber intake than daytime workers. More precisely, relative to daytime workers, both shift-work groups showed higher CHD hazard ratios at lower fiber intakes. These associations weakened with higher fiber consumption, reflecting a statistically significant interaction between fiber intake and work schedule.
In addition, meat avoidance was associated with a 10.4 % lower risk of CHD compared with meat intake, but this association was not observed across worker groups. In this study, meat avoidance was defined as consuming no processed meat and no unprocessed red meat (beef, pork, or lamb). Unlike fiber intake, meat avoidance did not show a statistically significant interaction with work schedule, indicating that its association with lower CHD hazard was similar across all worker groups. This should be expected based on current cardiovascular recommendations.
Notably, the reduction in CHD risk with meat avoidance was independent of fiber intake, indicating that perhaps the former achieves its effects by driving down saturated fat and heme iron intake, reducing blood lipids and systemic inflammation, or improving gut microbiome composition.
Interactions between fiber intake (in grams) and work schedule showed that night shift workers would need about 19 g/day of fiber to reduce their CHD risk to that of daytime workers. Shift workers with no or little night work required about 15 g/day of fiber. The risk drops below that of daytime workers with higher fiber intake than this, although the researchers caution that this apparent crossover reflects the statistical interaction in the Cox regression model and does not imply that shift work becomes protective at high fiber intake levels.
No sex-specific differences in CHD risk were found, irrespective of shift work.
Higher fiber intake was associated with a relative attenuation of CHD hazard, particularly among night shift workers. The authors suggest this may reflect the higher baseline cardiovascular stress associated with this work schedule. This type of shift work is associated with higher blood pressure, inflammation, and circadian disruption compared to daytime workers.
This is not a causal association, caution the researchers, but the reflection of the statistical interaction between these parameters in the Cox regression model they used. These results do not extrapolate to other cardioprotective dietary factors, such as anti-inflammatory omega-3 fatty acids. Moreover, meat intake is correlated with other beneficial dietary factors, like protein, iron, and vitamin B12. This precludes blanket bans on meat consumption in favor of a tailored approach.
Study limitations
The study has several limitations. Dietary habits were assessed only at baseline, so changes over time were not captured. There is also the possibility of residual confounding from lifestyle factors not included in the analysis, such as eating at night. In addition, higher dietary fiber intake may not be appropriate for certain individuals with specific medical conditions. Finally, the findings may have limited generalizability, as the cohort consisted primarily of middle-aged adults.
In fact, higher fiber intake is not a universal cure for high-risk individuals. It does not replace the need for other cardiovascular protective factors, such as physical exercise, good sleep hygiene, and avoiding smoking.
Future studies should have long-term follow-up, more diverse samples, and a granular assessment of cardiometabolic risk factors to validate these findings.
Tailored nutrition could support shift workers
The study showed interactions between dietary fiber intake and night shift work on CHD risk in middle-aged adults. A modest reduction in CHD risk was linked to meat avoidance. With increasing fiber intake, the risk in night shift workers was lower.
Overall, the findings indicate that higher daily fiber intake may help attenuate the elevated HRs associated with night shift work.
This indicates the potential for a tailored dietary plan targeting this subgroup, which would add to the relevance of the AHA’s Life’s Essential 8 recommendations.
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