The modern human body contains ancient genetic codes. These codes were programmed as our ancestors synchronized their activities to daylight, darkness and seasons of the year. The codes primed them to hunt and gather during daylight and to rest and rejuvenate at night. Our bodies still operate this way. Hundreds of body rhythms such as heartbeat, breathing, blood pressure, temperature, hormones and digestion rise and fall in predictable cycles.

Many of these cycles peak and ebb each day. The level of light entering the eye triggers hormone shifts. Environmental cues such as clock time, birds singing and traffic noise add to the body's information about light. The body then sets its biological clock. This clock acts like the choreographer of an intricate dance involving hundreds of body rhythms. Body functions become finely tuned to each other and to the environment.

Shiftwork disrupts this complex dance as the switch to night work triggers changes in body rhythms. The changed rhythms start to adjust to new cues but they adjust slowly and at different rates. They become out of sync with each other and with the environment. The result is internal chaos, like an orchestra with instruments being played at different times.

The same disruption of rhythms occurs when flying across several time zones. It can take several days for the body to recover from jet lag. The greater the time zone change the greater the recovery time.

Shiftwork creates a state like perpetual jet lag. The body may recover after several days off, but it is forced again into disharmony when night work resumes. Even permanent nights do not overcome the problem because the usual time cues change on days off. Some shiftworkers find the only way to feel well is to stop working nights. Others adapt more easily and experience fewer problems. As we age we become less tolerant of shiftwork.

What impact does shiftwork have on health? There are many gaps in our understanding of shiftwork and its effects on health. Modern technology is researching ways to overcome or lessen shiftwork stress. To date, simple and workable solutions have not been found. What is known, however, is that shiftwork has been associated with increased sleep problems, fatigue, gastrointestinal complaints, depression, anxiety, heart disease and substance abuse. Accidents and mistakes are more common on the night shift.

How can the effects be overcome?

Good health habits may help to reduce some of the wear and tear of shiftwork and promote feelings of wellness. For instance, adequate sleep is essential for health. Shiftworkers need a proper dark and quiet environment when they must sleep during the day. Then, when they finish a period of shiftwork, they must allow themselves a chance to recover normal body rhythms and catch up on lost sleep.

Exercise and recreation help to re-establish the cycles to which the body is accustomed. Good communication within the family can help everyone understand the person's need for changed patterns of sleep. A wise choice of foods may be of particular benefit in helping the body cope with the stress of changing body rhythms.

What is the relationship between nutrition and the stress of shiftwork?

For anyone, poor nutritional choices place a stress on normal body function. For those who do shiftwork, the change in schedule puts an extra strain on the body. The body produces lower levels of the hormones and enzymes needed for digestion during the nighttime. Therefore, changes in night-time eating patterns may be necessary to accommodate differences between daytime and night-time digestion.

Digestion slows down at night. The body turns its attention to growth, repair, rest and recovery. For instance, the wave of food propelling motion in the gut slows down. Hormone levels that affect digestion change at night. Although digestion does not stop completely, it is reduced. As a result, shiftworkers often experience unwanted weight changes, heartburn, diarrhea and other gastrointestinal problems.

It is not clear whether certain food choices and eating during the night are the cause of these problems or if they are aggravating factors. It seems prudent to adjust food intake until we understand more about night-time digestion. Choose smaller amounts of easily digested foods. Compared to larger meals, food intake spread out over more frequent feeds and coffee breaks may also lighten the load.

Since fat stays in the stomach longer and needs extra steps for digestion, fatty foods are harder and slower to digest. Avoiding fatty foods often eases digestive complaints like heartburn. Individual differences in digestion and tolerance to foods vary widely. Following are some hints that may help food digestion during shiftwork:

Choose foods that are not fried and watch for hidden fat in snack foods and baked items. Use butter, margarine and salad dressings sparingly.
Choose lower-fat milk and milk products. Avoid fatty and highly spiced luncheon meats. Choose lean meats and keep portions small. Try lower-fat cheese and yogurt as substitutes for meat.
Fruits, vegetables and whole-grain breads and cereals should comprise most of the night-time food choices. These foods are easy to digest and nutritious, and they provide quick energy. Choices can include whole-wheat bread, bagels, crackers, fresh fruit, juices, salads and low fat muffins.
Replace large, full course meals with soup and sandwiches.

What about overall nutrition for shiftworkers?

Healthy food choices are especially important to help offset the wear and tear of shiftwork. Why? Our bodies contain billions of cells. Each cell has a special job such as producing a digestive enzyme or helping the body defend itself against viruses.

Each cell requires a team of nutrients to do its job. Cells cannot operate if their team fails to shows up for work. Shiftworkers who eat poorly aggravate the wear and tear cause by desynchronized body rhythms.

What about caffeine and other beverages at night?

Coffee and other caffeine containing beverages such colas promote alertness but it becomes a sleep stopper if consumed up to six hours before sleep is planned. Coffee can also aggravate some digestive complaints.

There are several beverages to drink instead that do not interfere with digestion or sleep. Cold water, sparkling water, other non-caffeine containing carbonated beverages and fruit juices can quench thirst and not alter sleep. It may be helpful to drink fewer liquids by the end of a night shift to reduce bathroom needs during the sleep period.

Should eating patterns change during waking hours?

A breakfast eaten before a day-time sleep should be light to avoid interfering with sleep. Cereal, toast, fruit and muffins are good breakfast choices. A glass of warm milk may promote sleep.

After waking from day sleep, some shiftworkers find a traditional supper difficult to eat. Breakfast foods are a fine substitute. Regardless of what type of food (even cereal) is chosen for this meal, it is nice to enjoy sitting with the rest of the family for the evening meal.

Some final tips

The number of meals and amounts eaten during a night shift may be less than during a similar twenty-four hour period on a day shift. The important thing is to focus on eating a good variety of healthy foods following Canada's Food Guide to Healthy Eating. The attention paid to food choices and sound nutrition will benefit overall health and well-being. It is time well spent!

Night Shift Eating Avoiding common pitfalls