Objective: Shift work is associated with adverse health outcomes, and an unhealthy diet may be a contributing factor. We compared diet quantity and quality between day and shift workers, and studied exposure-response relationships regarding frequency of night shifts and years of shift work.
Methods: Cross-sectional general population data from the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) cohort was used. Dietary intake was assessed in 1993-1997 among adults aged 20-70 years using a food frequency questionnaire. We calculated energy intake, the Mediterranean Diet Score (MDS) and WHO-based Healthy Diet Indicator (HDI). In 2011-2014, we retrospectively identified 683 shift workers and 7173 day workers in 1993-1997. Using multivariable-adjusted linear regression analysis, we estimated regression coefficients (β) and 95% confidence intervals (95% CI) of the differences in dietary intake between day and shift workers.
Results: Shift workers had a higher energy intake than day workers (β:56 kcal/d, 95% CI 10-101), and a higher consumption of grains, dairy products, meat and fish (P<0.05). The difference in energy intake was largest for shift workers with ≥5 night shifts/month. They consumed 103 kcal/d (95% CI 29-176) more than day workers. No associations were found with MDS and HDI.
Conclusion: Shift workers and particularly those with a high frequency of night shifts had a higher energy intake than day workers. Regardless of number of night shifts and years of shift work, shift workers had similar diet quality as day workers. This suggests that increased energy intake among shift workers may contribute to shift work-induced adverse health outcomes.