DR. GOLDMAN'S BLOG

Read this if you do shift work

Night shift workers face increased risk of obesity, diabetes and even cancer. @NightshiftMD says the problem has more to do with when you eat than when you sleep.
Research suggests people who work nights face increased risk of breast, prostate and skin cancer. (Fulltimegipsy/Shutterstock)

One in four Canadians does shift work, and one in five works nights, according to the Workers Health and Safety Centre. 

It's a lifestyle that can be hazardous to your health. 

People who do shift work and especially night shift on a regular basis have higher rates of obesity, Type 2 diabetes and high blood pressure.

Those are risk factors for cardiovascular disease, so it's no surprise that chronic shift workers are more likely to get heart attacks, strokes and heart failure at some point in their lives. They have higher rates of ulcers and other gastrointestinal problems. They are also at increased risk of kidney disease.

In 2007, the World Health Organization said shift work was a probable cause of cancer. People who work nights are at increased risk of breast, prostate and skin cancer. Shift workers tend to be tired all the time. They are also more likely to suffer from depression.

Humans have evolved to sleep at night and be awake during the day. But as soon as you begin working a string of nights, the brain's internal clock begins to shift so that you can be awake at night and sleep during the day. It's a process that takes many days and requires that you stick with being up at night and asleep during the day even on days off. 

The body's internal clocks

In a new study, researchers examined the effect in healthy volunteers by having them do simulated night shifts. After three such night shifts in a row, the brain's internal clock was two hours out of sync. That was expected since the process of adjusting the brain's clock is gradual.

What was completely unexpected is that the clocks inside the volunteers' digestive tracts (the clocks that tell us to eat during the day and to fast at night) adjusted to nights extraordinarily quickly. While the brain's clock was just two hours out of sync, the digestive clock had jumped by a whopping 12 hours. 

For example, if it was midnight  for the volunteers, the clock in their brain said it was 2 a.m., and the clocks in their digestive tract said it was noon.

With signals that conflicted, it's no wonder their metabolism was disrupted. And it took just three nights for that to happen.

Until this study, researchers assumed that night shifts disrupt the sleep-wake which in turn disrupts other bodily processes.  No one knew that the clock inside people's digestive organs that controls eating and fasting could be changed so profoundly and so quickly while the brain's clock barely changed at all.

As part of the study, the researchers identified a large number of markers of abnormal metabolism in the bloodstream of shift workers. 

Those markers indicated that the volunteers were laying down abdominal fat instead of burning calories. That would help explain why they are more likely to gain weight and develop diabetes.

It's plausible that changes in the metabolism of shift workers alter the activity of cells involved in the development of cancer later in life. Once those processes are identified, researchers may be able to identify the genes that control them, and perhaps even prevent cancer in shift workers.

And that's not the only news. This study is also the first to show how alterations in the kidney's clock put shift workers at risk of kidney disease. 

The most important implication of the study is that the health risk comes not from working at night but from eating big meals at night. Experts have come around to the hypothesis that the best way to prevent obesity, diabetes and other direct health problems in shift workers is to restrict calories during the night shift.

A recent study found that restricting feeding in mice kept awake at night shifted their digestive clocks back to the normal routine of eating during the day and fasting at night. There is some evidence that doing so in humans may help prevent diabetes.

A lot more research needs to be done to prove that when you eat is more important than when you sleep. Thanks to this study, researchers will be able to do blood tests that measure the effectiveness of tactics that minimize the risks of shift work.

In the meantime, experts recommend that night shift workers set aside a block of seven to nine hours for sleep during the day. Use blackout curtains and nightshades to block out light, and earplugs and sound machines to block or mask out noise.

If you want to apply the latest research related to diet, eat as little as possible at night.

Experts recommend avoiding fried foods at night because they are hard to digest. Stick with light broths, rice and yogurt plus foods rich in protein such as eggs, peanut butter, tuna, peas, beans and roast turkey.

Drink lots of water during your shift. After coming home from a night shift in the morning, eat carbohydrate-rich foods like bread, cereals, muffins and fruit because they make you sleepy.  

The study has some important implications for people who don't work nights but like to snack at night. If you don't want to gain weight, lay off fried foods, fats and carbohydrates. 

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