Do you work unusual hours? Do you wonder which meal is better suited to which time of the day? Do you worry about the effect shift work may have on your health?
Maybe you work in the emergency services; maybe you are on the night shift at a big factory; you might even work in the hospitality industry. There are many occupations that involve working outside what we might call "normal" hours. So how do you ensure you are maintaining a way of eating that supports you health, while dealing with the unique challenges that shift work presents?
Firstly, what do we mean by shift work?
Shift work is any occupation that involves regularly working outside the "normal 9 to 5" pattern. This might involve really early starts, very late finishes, or even real "back-of-the-clock" stuff, where you work all the way through the night, and get home about the time everyone else is leaving to start work. In addition, your shifts may be fixed - the same hours every time; or rotating - a stretch of early shifts, a couple of days off, then a stretch of lates, followed by another couple of days off.
How can shift work affect our health?
Compared to people who work "regular" hours, shift workers have a higher risk of cardiovascular disease (disease of the heart and blood vessels, including stroke) and Type 2 diabetes. Interestingly, it seems that anyone who tends to eat late into the night - after around 8pm - may have a higher risk of chronically elevated blood glucose levels (hyperglycaemia), as well as an increased risk of developing Metabolic Syndrome.
Metabolic Syndrome is a cluster of conditions that increase your risk of developing heart disease, stroke and Type 2 diabetes:
elevated blood pressure (but not enough to be diagnosed with hypertension)
elevated levels of triglycerides in the blood (a type of fat)
elevated blood glucose levels (but not enough to be diagnosed with Type 2 diabetes)
lower levels of "good cholesterol" (high-density lipoprotein, or HDL)
a waist circumference above a certain measurement (this type of fat storage pattern is an indication of excess fat around your internal organs, also called visceral fat)
Why this extra risk?
Firstly, we need to look at our body clock.
Our body clock is what controls our sleep/wake cycle, also known as circadian rhythm. We have a “master clock” in a part of our brain called the hypothalamus. This little part of the hypothalamus (called the suprachiasmatic nucleus) receives light signals from the eyes via the optic nerve, and this helps regulate our circadian rhythm cycle, which is approximately 24 hours in length.
Throughout the circadian rhythm cycle, this master clock co-ordinates how efficiently certain biological processes work. This is designed to match the efficiency of these various processes to the sort of activity you would expect to be doing at that time in the sleep/wake cycle. Things like digestion and absorption of food, growth and repair of body tissues, even your body temperature is affected. For the nerds who would love some more detail about how this works on a cellular level, check out this video.
Consequently, when we eat through the night we are out of step with our circadian rhythm, and the efficiency of our digestion and absorption processes is turned down to the low setting. As a result, our body deals with this food differently, leading to some very interesting responses.
Blood glucose levels
Research shows that our blood glucose response to food can be significantly different depending on what time we eat. One study compared a glucose drink consumed at 8am, with the same drink consumed at 8pm. The blood glucose levels following the evening session were twice that of the morning session - and it was the exact same drink!
After those fairly startling results, the researchers looked for similar studies, and found nine others showing the same effect. They also found eight studies that showed a much greater insulin response to food eaten during the night. This makes sense as insulin is the hormone your body releases in response to the glucose level in your blood rising, so if the glucose level is higher, then your pancreas is required to pump out more insulin to return your blood glucose back to normal levels.
The usual advice may not be appropriate
As a Nutritionist, I would think the best way to calm down this scarily high blood glucose response would be to ensure you ate a high-fibre, low Glycemic Index meal during those small hours at work. The Glycemic Index (or GI) is an indication of how quickly the carbohydrate in a food or meal is digested and absorbed into the bloodstream. A high GI food will be digested and absorbed rapidly, and will cause your blood glucose levels to spike fairly quickly, then fall equally rapidly - think of that sugar crash you can have after eating something high in added sugar. A low GI food will take longer for your body to digest and absorb, and your blood glucose levels will rise slowly, won't reach as high a peak, and will come down slower too - meaning you have sustained energy for longer (no crash!). Low GI foods are often higher in fibre and more nutrient dense too, although this is not always the case. GI is just one more tool to guide your food choices, and shouldn't be used to classify foods as "good" or "bad".
However, one study compared a low GI meal and a high protein low carbohydrate meal, once again eaten in the morning and in the evening. Both meals produced larger blood glucose readings when they were eaten at night compared to when they were eaten in the morning, so very much in line with the previous research I mentioned. But when you compare both night-time results, the glucose response from the high protein low carb meal was only around a third of the glucose response from the low GI meal. So it seems reducing the carbs and pumping up the protein and non-starchy vegetables in the meal or snack you eat during your night shift might just be a better strategy than a low GI meal. Essentially, save most of your grainy carbs for the hours between 8am and 7pm.
It’s also interesting to view these results in light of other research that has shown there is no significant difference between the total energy intakes of day time workers and shift workers – so it’s not that shift workers are eating more kilojoules, it’s that their bodies are processing those kilojoules in a comparatively inefficient way, due to a mis-match between their body clock and their eating patterns.
So what’s the connection between these different daytime and night time glucose and insulin responses, and the health of shift workers?
We know that people with continually elevated blood glucose and insulin levels have a much greater risk of developing both CVD and T2DM.
That can’t be the only reason, can it?
No, to be fair, there are many other factors that can influence the type of food you choose to eat while on shift, or before and after shift:
How stressful your work is
If there are regular, scheduled meal breaks, or if you end up just grabbing food when you can
Drinking coffee or caffeinated sugary drinks to keep awake
The kind of food available when at work – what if the only food available is from snack-filled vending machines?
Is there a fridge at work to put your leftovers in, or a microwave to re-heat food?
What your workmates eat – it can be hard to resist food that people have brought in to share
If you regularly choose foods that are higher in added sugar and fat, even if you eat the same amount of energy as a non-shift worker this will further affect your blood glucose response, as well as the other conditions involved in Metabolic Syndrome.
I guess the next question is, what are some strategies I can use as a shift worker to reduce my risk of developing cardiovascular disease and Type 2 diabetes?
Before we dive into that, it might be time for a quick re-cap on what we’re aiming to eat in a 24-hour period:
5+ serves of fruit and veg
Around 6 serves of grains (that’s your breads, cereals, rice, pasta group), predominantly wholegrain
2 serves of dairy foods (or alternatives)
1 or 2 serves of protein foods (depending on whether you are a vegetarian or not)
If you work shifts, you’ll still be aiming for these food group servings in a 24-hour period, you’ll just be jiggling the timing of them around a bit to suit your work schedule and your body clock – and trying to avoid those big glucose and insulin spikes.
Here are my Top 4 Tips for shift workers:
1. Plan your food and meal timings:
With an eye on the food group serves and your shift schedule, plan out your meals and snacks. It will really depend on personal preferences (for example, if you prefer to eat breakfast foods in the mornings, or upon waking) and your shift start and finish times, but as a general guide for a night shift (working 10pm – 7am, going to bed at 9am and waking at 5pm):
7pm: dinner with family - eat your dinner (bigger meal, preferably before 8pm)
10pm: start work
11pm: small protein-rich snack at work
2am: protein-rich lunch sized meal - this will depend on your scheduled breaks
Try and have a “fasting window” of around 5 hours during your shift (likely after your “lunch”)
7am: leave work
7.30am: eat breakfast - aim to eat a typical breakfast when you get home after shift, an hour or so before going to bed (this way you’re not eating a big meal too close to lying down, avoiding any reflux issues)
9am: go to sleep
5pm: wake up - depending on your intended activity level (you might want to do some exercise before work), and how much time you have until your evening meal, you may like a small snack after waking.
This all adds up to breakfast, lunch and dinner with one or possibly two snack occasions. The only difference between this schedule and non-shift eating would be the recommendation for the “fasting window” during work – this would be comparable to an office worker eating lunch at midday, then not having a snack until they eat an apple on the way home in the car, for example.
2. Pack a lunchbox:
Go and get yourself a cooler bag, some of those little freezer cube thingies, and an assortment of reusable plastic containers with tight-fitting lids. Now you’ve got all you need to pack all the food you planned to eat in step one, and take it along to work. If you don’t have a fridge at work, this is even more important to keep your food chilled and safe to eat.
3. Pump up the protein at work:
Grainy carbs are our friend (think gut health, and decreased risk of cardiovascular disease, Type 2 diabetes and many cancers), but if you are a shift worker eating in the middle of the night, they are less friendly! Try and pack a smaller meal or snack that’s high in protein and low in carbs, in case you get the munchies towards the end of your shift. If you want some snacks on hand, try:
reduced-sugar yoghurt, grainy crackers and cheese, a small handful of nuts, hard-boiled eggs, vege sticks and hummus…
4. Watch the drinks:
If you do drink sugary drinks at work, try and reduce the number you have. It’s easy to consume a lot of energy very quickly in this form, with very few (if any) beneficial nutrients. If you drink caffeinated drinks at work, try and give yourself enough time between your last dose of caffeine and the end of your shift, so as not to disturb your sleep when you get home.
If you'd like some ideas on food to pack for work, you might find these two resources very useful:
I would like to acknowledge the work of Gloria Leung PhD candidate from Monash University, Melbourne Australia. Her research in this area, along with additional research listed below, informed this blog post and the associated podcast episode.
Antunes, L.C., Levandovski, R., Dantas, G., Caumo, W., & Hidalgo, M.P. (2010). Obesity and shift work: Chronobiological aspects. Nutrition Research Reviews, June 2010. Retrieved from https://pdfs.semanticscholar.org/2f99/1b21656e2318aff38f9799d24c09a07d77dc.pdf?_ga=2.256698946.8145858.1569119641-1360602564.1569119641
Davis, R., Bonham, M.P., Nguo, K., & Huggins, C.E. (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 (no free access)
Gill, S., & Panda, S. (2015). A smartphone app reveals erratic diurnal eating patterns in humans that can be modulated for health benefits. Cell Metabolism, 22, 789–798. Retrieved from https://www.cell.com/cell-metabolism/pdfExtended/S1550-4131(15)00462-3
Kutsuma,A., Nakajima, K., & Suwa, K. (2014). Potential association between breakfast skipping and concomitant late-night-dinner eating with Metabolic Syndrome and proteinuria in the Japanese population. Scientifica, 14. Retrieved from http://downloads.hindawi.com/journals/scientifica/2014/253581.pdf
Leung, G.K.W., Huggins, C.E., & Bonham, M.P. (2017). Effect of meal timing on postprandial glucose responses to a low glycemic index meal: A crossover trial in healthy volunteers. Retrieved from https://reader.elsevier.com/reader/sd/pii/S0261561417314085?token=CB77021EE6C5F3C06DC0BB989069482AACA4DF4DA234A91D641ED3E1D0FDEF12F08D721243D56A25D8A886A140BE0437
Leung, G.K.W., Huggins, C.E., Ware, R., & Bonham, M.B. (ahead of publication). The Effect of Meal Timing on Postprandial Glucose and Insulin Response: A Meta-Analysis of Acute Experimental Trials [Abstract]. Presented ahead of publication at the 10th Asia-Pacific Conference on Clinical Nutrition 2018.
Nakajima, K., & Suwa, K. (2015). Association of hyperglycemia in a general Japanese population with late-night-dinner eating alone, but not breakfast skipping alone. Journal of Diabetes & Metabolic Disorders, 14 (16). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4396539/pdf/40200_2015_Article_147.pdf
Vetter, C., Dashti, H.S., Lane, J.M., Anderson, S.G., Schernhammer, E.S., Rutter, M.K., Saxena, R., & Scheer, F.A.J.L. (2018). Night shift work, genetic risk, and Type 2 Diabetes in the UK Biobank. Diabetes Care [online, ahead of print]. Retrieved from https://care.diabetesjournals.org/content/early/2018/01/31/dc17-1933.full-text.pdf
Vyas, M.V., Garg, A.X., Iansavichus, A.V., Costella, J., Donner, A., Laugsand, L.E., Janszky, I., Mrkobrada, M., Parraga, G., & Hackam, D.G. (2012). Shift work and vascular events: Systematic review and meta-analysis. British Medical Journal, 345. Retrieved from https://www.bmj.com/content/bmj/345/bmj.e4800.full.pdf