Chapter 5 - Food

Learning Outcomes

After reading through this chapter, you should be able to:

  • Describe the glycemic index.
  • Distinguish high, intermediate, and low glycemic index foods. 
  •  Explain the impact of these foods on alertness.
  •  Explain how digestion and hunger are affected by non-traditional hours of work.

Why think about food to manage fatigue?

As discussed elsewhere in this workbook, the ability to stay awake is largely related to whether you have had adequate rest and recovery. However, there are other factors that may contribute to feeling weary, sluggish, and more tired in general. One of these is low blood sugar. Many people underestimate or are unaware of the affect of low blood sugar on their ability to stay alert and safe

Digestion and hunger

As humans, we are programmed to be awake during the day and asleep at night. Many other processes also follow this pattern, including digestion. Digestion is programmed to be most efficient during the day and much less so at night. This is because digestive juices (stomach acids and enzymes) are mainly secreted during the day.

Food eaten at night is digested at a slower rate. This can often lead to feeling bloated or constipated and can cause heartburn and indigestion. Gastro intestinal upsets are very common in people who eat outside of traditional meal times. These upsets can be worsened by drinking tea, coffee, or alcohol. Research has found that night workers are five times more likely to get peptic ulcers than day workers.

Many people working outside traditional daytime hours also notice that their hunger patterns change and that they get hungry at unexpected times of the day.


Controlling blood sugar with food

Given that non-traditional hours of work affect digestion and hunger, it is not surprising that it is difficult to keep your blood sugar stable under such circumstances. A stable blood sugar level is an important ally in minimizing the ups and downs in energy levels that are common for shift workers.

The belief that snacks loaded with sugar cause a fast rise and fall in blood sugar has been recently disproved. The way blood sugar levels react to different foods is known as the glycemic index (GI) of foods.

High GI foods make your blood sugar levels rise and fall quickly, whereas low GI foods make your blood sugar level rise and fall slowly. High GI foods are ideal when you have been doing physical work or exercise and need energy quickly to recover. Low GI foods are ideal to keep an already stable blood sugar level from becoming too high or low. Low GI foods are also ideal for raising blood sugar slowly and avoiding the fast drop in blood sugar (and energy) that can occur after eating high GI foods. Low GI foods are ideal as regular snacks across a shift to help avoid big changes in your energy levels.

Research into GI foods also holds important implications for people with diabetes. In general, medical practitioners recommend that diabetics avoid high GI foods to help regulate blood sugar levels. But high GI foods can be useful as a pick-me-up for non-diabetics, particularly after physical work or exercise. More often than not, however, low GI foods will be more useful in your day-to-day life.

Low-fat protein strategies

Research also suggests another eating strategy for shift workers: evidence shows that eating low-fat protein foods can help you stay awake. This is due to a process involving the amino acid tyrosine and leads to increases in the levels of stimulating chemicals in your body.


Examples of high GI foods

White or whole grain bread
Cornflakes or Coco Pops
White or quick brown rice
French fries
Rice crackers
Puffed corn or rice cakes
Baked or mashed potato
Breakfast bars

Examples of low GI foods

Oranges or orange juice
Baked beans
Fruit bread
All bran, porridge, muesli
Low-fat yogurt
Peanuts or cashews
Noodles or pasta
Apples or apple juice
Oat bran or grain bread

Examples of intermediate GI foods

Basmati rice
Rye or high-fibre bread
Full-fat ice cream
Flavoured milk drinks
Sweet corn
Soft drinks
Cranberry juice

Examples of low-fat protein foods

Low-fat dairy products
Hard boiled eggs
Cooked and canned fish
Lean chicken, beef, or lamb
Protein shakes


What type of GI foods do you normally consume at work or before work: high, intermediate, or low? Give examples.


Are there any food changes you should consider, based on what you now know about the GI of foods? If so, what are they?



Where to from here?

It is likely that at least some of the information in this chapter is new to you. You may have picked up some fresh strategies. Try things for a while and see how they work for you. Keep in mind that you are more likely to notice a difference using these strategies if you apply them when you are tired.

It is also important to maintain a balanced diet. In general, the evidence suggests that a low-fat diet comprised mainly of low and intermediate GI foods along with some good quality protein is most beneficial. In addition, it is important to consider the level of fibre in your diet (from fresh fruit and vegetables) as well as the levels of minerals and salt. The recommended daily salt intake is 3.8 grams per day to replace the amount lost daily through perspiration and to ensure your diet provides sufficient amounts of other essential nutrients. However, any more salt than this can result in high blood pressure, which can lead to stroke, heart disease, or kidney disease.

Case study

man eatingJeff is a 58-year-old maintenance engineer who has been working in the aviation industry since he was 16 years old. His three children are grown up and have their own homes and families. Jeff and his girlfriend Lisa have been together for seven years.

Lisa prepares Jeff’s meals. When he has a night shift, afternoon shift or an early morning shift, she packs whatever they would have eaten had they been together. Jeff cooks his meals in the kitchen at work and often prepares steak and eggs, reheats meatloaf, or roasts pork chops. This is the way things were before Lisa was around, and this is the way they have stayed.

The problem is that in the last few years, Jeff has been getting really bad stomach pains whenever he eats a heavy meal on the night shift. Jeff has only a few more years until he plans to retire and he doesn’t want to change the way he does things now. Jeff’s doctor has been saying that the pains are associated with the type of food that he eats on nights, but Jeff thinks he’ll be okay.

Jeff actually has a serious case of peptic ulcer. It’s unfortunate that Jeff doesn’t listen to his doctor because ulcers can be treated quite easily with diet changes and short-term daily medication.


checkmark Knowledge Check

  • Why might Jeff experience stomach problems after eating a heavy meal on the night shift?
  • What changes might Jeff make to his diet to help reduce his stomach problems?
  • Why are low GI foods generally appropriate when working shifts?
  • What effect does a stable blood sugar have on energy levels?
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