The number of UK employees working night shifts has increased by 9% between 2011 and 20161. As we move towards a 24-hour economy and the need for 24-7 healthcare provision, the prevalence of night shift work is forecast to increase. While the transition away from the traditional 9 a.m. to 5 p.m. working pattern may be advantageous to the economy and assist in meeting the increasing demand for health care, long-term exposure to night shift work may have a cost. Large-scale observational studies in North America have shown a 5% increased risk of developing type two diabetes for every 5-years of rotating shift work (a mixed shift schedule including at least three night shifts per month)2. In Canada, where the prevalence of shift work is 33% (compared to about 15% in the UK) it is estimated that shift work exposure attributes 7.3% to coronary events in the population3.
We know that diet is a key factor in the development and management of type 2 diabetes and cardiovascular diseases. Given the observed health disparities associated with time of working hours we need to understand:
i) how night shift work influences dietary intake
ii) if diet can help reduce the risk of developing type two diabetes and cardiovascular diseases in shift workers.
Over recent decades observational studies have reported that night shift workers in particular tend to consume a less healthy dietary pattern – with higher dietary energy density and higher intake of sugars-sweetened beverages4,5. More recent laboratory controlled ‘chrono-nutrition’ (the interaction between nutrition and time of eating) studies have found that consuming energy during the night, compared to during the day, has an acute detrimental impact on blood lipids and glucose6,7. Although limited studies have tested the interaction between nutrients and time of eating, where evidence does exist the health outcomes of a poor diet may be potentiated when consumed during the night8.
Improving the diet of shift workers to be in-line with current UK healthy eating recommendations is clearly an important step to improving the nutritional wellbeing of shift workers. However, implementing dietary changes are challenging in this population group due to the availability of food and also human biological processes interlinking circadian and metabolic systems. For example, we know that the hunger hormone ghrelin is higher during the night9 – possibly driving the increased consumption of snacks and sugar sweetened beverages observed in night workers.
Specific evidence based guidelines for night workers are yet to be established. Chrono-nutrition is an emerging field of nutritional science. Current and planned studies in this field will be key to understanding if we need to provided more prescriptive dietary recommendations for night workers to offset the effect of eating out of sync with our body clock. “Do we need to specify time of intake guidelines alongside healthy eating guidelines?” is an important research question. A pilot study being conducted in Australian shift workers is testing the hypothesis that avoiding food intake between 1 a.m. and 6 a.m. will improve blood glucose and lipids in night workers10. This is an exciting area of work – however researchers need to not only determine the effectiveness of such interventions, but also the acceptability and practicalities of interventions to employees working night shifts.
Author: Dr Rachel Gibson RD. Lecturer in Nutrition and Dietetics at King’s College London and Work Ready Dietitian. Research interest: Working hours, dietary behaviours and cardio-metabolic health.
- Trade Union Congress. Number of people working night shifts up by more than 250,000 since 2011, new TUC analysis reveals | TUC. (2017). Available at: https://www.tuc.org.uk/news/number-people-working-night-shifts-more-250000-2011-new-tuc-analysis-reveals. (Accessed: 12th November 2017)
- Pan, A., Schernhammer, E. S., Sun, Q. & Hu, F. B. Rotating night shift work and risk of type 2 diabetes: two prospective cohort studies in women. PLoS Med 8, e1001141 (2011).
- Vyas, M. V et al. Shift work and vascular events: systematic review and meta-analysis. BMJ 345, e4800 (2012).
- Gibson, R. et al. Sex differences in the relationship between work patterns and diet in British police force employees: a nested cross-sectional study. Proc. Nutr. Soc. 75, E20 (2016).
- Nea, F. M., Kearney, J., Livingstone, M. B. E., Pourshahidi, L. K. & Corish, C. A. Dietary and lifestyle habits and the associated health risks in shift workers. Nutr. Res. Rev. 28, 143–166 (2015).
- Al-Naimi, S., Hampton, S. M., Richard, P., Tzung, C. & Morgan, L. M. Postprandial metabolic profiles following meals and snacks eaten during simulated night and day shift work. Chronobiol. Int. 21, 937–47 (2004).
- Scheer, F. A. J. L., Hilton, M. F., Mantzoros, C. S. & Shea, S. A. Adverse metabolic and cardiovascular consequences of circadian misalignment. Proc. Natl. Acad. Sci. U. S. A. 106, 4453–8 (2009).
- Morgan, L. M., Shi, J.-W., Hampton, S. M. & Frost, G. Effect of meal timing and glycaemic index on glucose control and insulin secretion in healthy volunteers. Br. J. Nutr. 108, 1286–91 (2012).
- Qian, J., Morris, C. J., Caputo, R., Garaulet, M. & Scheer, F. A. J. L. Ghrelin is impacted by the endogenous circadian system and by circadian misalignment in humans. Int. J. Obes. 1 (2018). doi:10.1038/s41366-018-0208-9
- Bonham, M. P. et al. Does modifying the timing of meal intake improve cardiovascular risk factors? Protocol of an Australian pilot intervention in night shift workers with abdominal obesity. BMJ Open 8, e020396 (2018).