Shift work and carbohydrates - more or less? How meal choice impacts health outcomes for shift workers

The proportion of carbohydrate, fat and protein in food choices for shift workers when eating at night has the potential to improve post-meal blood sugar control, which may reduce the risk of developing insulin resistance and type 2 diabetes according to new research by the Monash University Department of Nutrition, Dietetics and Food.

Shift work - long nights, sleeping during the day and chronic disruptions to circadian rhythms. The life of a shift worker means food is often consumed throughout the evening and over night when most of us would usually be relaxing on the couch or sound asleep. Shift workers have an increased risk of chronic lifestyle (namely metabolic) conditions including type 2 diabetes and cardiovascular disease, which may be partly driven by eating behaviours. Understanding the impact of nutrition choices on the health outcomes of shift workers presents a very real opportunity to improve health outcomes [1].

You might be wondering what the big deal is. According to the Australian Bureau of Statistics, shift workers make up 16% of the Australian workforce - this equates to 1.4 million people [2]. Given the heightened risk of developing chronic lifestyle conditions, and the associated social and economic impacts, determining what can be done to optimise the health of shift workers is imperative. Addressing the type of food our shift workers consume and when they consume it may be one of these solutions, and is the focus of Associate Professor Maxine Bonham and her team's research.

For shift workers “what you eat, not just when you eat, is important, as we know that meals consumed overnight are associated with disruptions to metabolic processes,'' explained Maxine. PhD researcher Gloria Leung from Maxine’s team demonstrated this when she gave volunteers the same sugary drink on two separate days, once in the morning, and once at night. She found that although the drink contained the same sugar load, at night the volunteers’ blood sugar levels soared [3]. Gloria noted that “We know that the body is less efficient at clearing sugar, and potentially fats, from the blood after the same meal eaten at night compared to in the morning, and it’s because of this that eating during the night over a period of months or years contributes to poor metabolic health.”

“...the body is less efficient at clearing sugar, and potentially fats, from the blood after the same meal eaten at night compared to in the morning…”

Knowing that the metabolic response to the same meal will be different when eaten in the day versus night, and the fact that we have such a large proportion of the population on night shifts, the team wanted to find out if manipulating a meal’s macronutrient composition could impact how the body responds. “We wanted to know if adjusting the macronutrient composition of the meal resulted in a ‘healthier’ metabolic response at night,” PhD researcher Rochelle Davis, also from Maxine’s team, commented. Her recent study, published in the Journal of Clinical Nutrition, looked at how the body’s response to a meal at night changed when the proportions of carbohydrate and protein were manipulated.  She swapped ingredients in a pasta meal with high protein alternatives boosting the protein content from 15% to 41%, and simultaneously reducing the carbohydrate proportion from 46% to 29%. She found that reducing the carbohydrate portion of a meal at night in favour of more protein was effective in reducing participants’ blood glucose responses by 71.4% [1] - creating a ‘healthier’ metabolic response.

These studies add to other evidence from Maxine’s research group which is helping to create a picture of the link between food choices at night and not only metabolic health, but wellbeing at work in general. The research team has also found that feelings of ‘sleepiness’ increased when consuming a meal high in fat and sugar compared to a healthier meal at night [4]. This is particularly important in the context of workplace health and safety, and employee productivity, with the Sleep Foundation noting that sleepiness can cause us to make more errors and react slower than we do when we’re alert [5]. In fact, people often make poor judgement calls relating to their state of mind and abilities, ‘believing that they are able to handle important decisions and tasks, when in fact they are not’ [5]. This is pretty concerning when you consider the role of many shift workers (e.g. emergency department staff).

“This highlights the need for our work in order to develop effective strategies aimed at keeping shift workers healthy. These are important studies that are going to be able to inform relevant dietary guidelines for shift workers” explain Dr Bonham.

“The bottom line: meal composition matters, particularly when consumed at night.”

The bottom line: meal composition matters, particularly when consumed at night. Maxine recommends “those who have no choice but to eat at night should favour meals with a higher protein content and a moderate amount of fat combined with complex carbohydrates rather than meals high in fat and refined carbohydrate”. By following this type of meal pattern, shift workers are better able to use food to have a more positive impact on long term health and take steps towards reducing their risk of chronic health issues such as diabetes, cardiovascular disease and obesity [1].

Maxine’s team are continuing this work with a world-first study trialling weight-loss interventions in night shift workers. The study, Shifting Weight In night shiFt workers (SWIFT) will use diet plans that are flexible to the demands of working night shifts. To learn more about the study and eligibility criteria visit the website. We are also working to develop practical and achievable dietary recommendations for Australian shift workers. Part of this process is understanding the factors that influence shift workers’ eating habits. If you would like to share your “food story” as a shift worker click here to learn about the Shift Work Photovoice Study.

More Information

Associate Professor Maxine Bonham is a Registered Nutritionist (Australia/UK) and an academic staff member and researcher within the Department of Nutrition, Dietetics and Food. Maxine’s expertise is in the successful development and oversight of nutrition intervention programs that favourably impact metabolic health. Click here to access Maxine’s research profile. You can follow Maxine on Twitter via @MaxineBonham.

Rochelle Davis is a PhD candidate at Monash Department of Nutrition, Dietetics and Food whose research explores circadian rhythms in metabolism, and meal timing strategies to improve risk markers for health. Click here to access Rochelle’s research profile.

Gloria Leung, a PhD candidate at the Monash Department of Nutrition, Dietetics and Food, is passionate about improving the health of shift workers and is focusing her research on developing an evidence base around healthy eating at night. Click here to access Gloria’s research profile.

Publication information

Davis R, Bonham MP, Nguo K, & Huggins CE. (2019). Glycaemic response at night is improved after eating a high protein meal compared with a standard meal: A cross-over study, Clinical Nutrition, https://doi.org/10.1016/j.clnu.2019.06.014.

Click here to access the paper published in Clinical Nutrition.

Bonham MP, Kaias E, Huggins CE, Davis R, Leung GK, Eikelis N, Shaw E, Murgia C, Effects of macronutrient manipulation on postprandial metabolic responses in overweight males with high fasting lipids during simulated shift work: A randomized crossover trial, Clinical Nutrition, https://doi.org/10.1016/j.clnu.2019.02.018

Click here to access the paper published in Clinical Nutrition.

Clinical Nutrition is ranked 6 out of 86 in category Nutrition and Dietetics and has an impact factor of 6.402

Photo by Ryan Puncy on Unsplash.

References

1. Davis R, Bonham MP, Nguo K, & Huggins CE. (2019). Glycaemic response at night is improved after eating a high protein meal compared with a standard meal: A cross-over study, Clinical Nutrition, https://doi.org/10.1016/j.clnu.2019.06.014

2. Australian Bureau of Statistics, 6105.0 - Australian Labour Market Statistics, Oct 2010, accessed on March 31st, 2019, http://www.abs.gov.au/AUSSTATS/abs@.nsf/featurearticlesbyReleaseDate/5461A9DAE97FF759CA2578C300153388?OpenDocument

3. Leung GK,Huggins CE, Bonham MP, (2019) Effect of Meal Timing on Postprandial Glucose Responses to a Low Glycemic Index Meal: A Crossover Trial in Healthy Volunteers, Clinical Nutrition, https://doi.org/10.1016/j.clnu.2017.11.010

4. Bonham MP, Kaias E, Huggins CE, Davis R, Leung GK, Eikelis N, Shaw E, Murgia C, Effects of macronutrient manipulation on postprandial metabolic responses in overweight males with high fasting lipids during simulated shift work: A randomized crossover trial, Clinical Nutrition, https://doi.org/10.1016/j.clnu.2019.02.018

5. National Sleep Foundation, The relationship between sleep and industrial accidents, accessed on March 31st, 2019, https://www.sleepfoundation.org/excessive-sleepiness/safety/relationship-between-sleep-and-industrial-accidents