Shift work is not associated with dietary acid load in the NHANES

Changes in eating habits and food preferences caused by circadian rhythm disruptions in shift workers increase the risk for chronic diseases. Several studies demonstrated that shift work exerts adverse effects on various risk factors for cardiometabolic disease and cancer. Moreover, shift work leads to altered eating patterns, including diets low in alkaline foods (such as vegetables, fruit and legumes) and high in acidogenic foods (such as meat, fish and cheese). Previously not examined, this imbalance could result in a high dietary acid load (DAL). DAL has been linked to low-grade metabolic acidosis, tissue inflammation and other metabolic alterations. The aim of this study was to investigate the hypothesis that shift work is positively associated with an increased DAL.

The authors used cross-sectional data from the National Health and Nutrition Examination Surveys (2007–2010). The sample for this analysis was drawn from a representative multistage-probability sample of US civilians. DAL estimations included potential renal acid load (PRAL) and net endogenous acid production (NEAP). Acid load scores and nutrient intake were compared between regular day workers (n = 3,814; mean age, 43.7 ± 0.3; mean body mass index (BMI), 28.6 ± 0.1; females 46.9%) and shift workers (n = 881; age, 37.4 ± 0.6; BMI, 28.4 ± 0.3; females 48.1%). Evening/night shift workers combined with rotating shift workers were contrasted to participants on a regular daytime schedule.

Potassium and magnesium intake were significantly lower in shift workers, whereas no significant differences with regard to total energy intake were found. The authors found significantly higher crude NEAP_F scores in shift workers (mean: 61.8 ± 1.2 mEq/day) compared to regular day workers (mean: 58.7 ± 0.5 mEq/day, P = 0.023). After adjustment for confounders, however, this association remained no longer significant. There were no significant intergroup differences regarding NEAP_R and PRAL_R.

This study revealed significant differences in crude NEAP_F scores between shift workers and day workers. After adjustment for confounders, this association was no longer significant. Such discrepancy is probably because of the scarce homogeneity in the analyzed sample which represents the main limitation of this study. Thus, the results did not confirm the hypothesis that shift work is associated with elevated DAL scores. Importantly, the data suggest significant intergroup differences in nutrient intakes without confirming our initial hypothesis with regard to DAL.

In light of the detrimental health outcomes associated with an increased DAL, this study reinforces the call for evidence-based dietary guidelines in shift workers. Studies in other shift working populations are thus warranted.