Shift Work Linked to Gut Problems

Among a growing body of evidence that shift work is hard on your health, a new study finds that it can trigger irritable bowel syndrome.

March 23, 2010

Switching shifts can be a pain in the gut, but you can protect yourself.

RODALE NEWS, EMMAUS, PA—Shift work is hard on people, and not just for the crazy schedule. A few years ago, the International Agency for Research on Cancer dubbed it a probable carcinogen after studies found that shift workers were more likely to suffer from breast and colon cancers than the rest of the population. Shift work has been associated with other diseases as well, including obesity, heart disease, and, according to the results of a study recently published in the American Journal of Gastroenterology, irritable bowel syndrome (IBS), a difficult-to-diagnose condition characterized by abdominal pain, cramping, constipation, bloating, and diarrhea.


THE DETAILS: The researchers focused on a sample of 399 nurses working at a university hospital. Of those, 399,214 reported working day shifts only, 110 reported working night shifts only, and 75 reported working a combination of day and night shifts. The nurses also filled out questionnaires related to their gastrointestinal health, whether they suffered irritable bowel syndrome, constipation, or diarrhea, and the quality of their sleep (poor sleep quality has been linked in a few studies to IBS). While sleep quality didn't have a noticeable effect on whether shift workers had IBS, the shifts they worked did. Nurses who worked day-only shifts had the lowest rates of IBS, while nurses who worked a combination of day and night shifts had the highest. Nurses who worked combination shifts were also the most likely to suffer from mixed IBS, a condition in which IBS sufferers also experience diarrhea and constipation, while night-shift workers were most likely to suffer diarrhea-predominant IBS.

WHAT IT MEANS: Shift work can be hard on your gut, particularly if you're constantly changing which shift you work. Sandra Hoogerwerf, MD, assistant professor of internal medicine at the University of Michigan and lead author of the study, says one theory to explain why people who work shifts are more likely to have IBS has to do with the body's circadian rhythms. "We have these clocks in our gut that determine what happens every 24 hours," she says. "And the colon has its own clock that says you should have your bowel movements in the first six hours after you get up." When people constantly change when they're getting up and going to work, their clock is also constantly changing, she adds, and they get can get constipated, bloated, and start having other gastrointestinal problems associated with IBS.

Messing with your body's clock can have other problems as well, which is why scientists have deemed shift work a cancer-causer. Your body's circadian rhythm regulates more than just your sleep and your colon, Dr. Hoogerwerf says. It controls how your body metabolizes food, which is why studies have found people who eat large meals in the morning are less likely to become obese than people who eat large meals at night, and it affects when cells replicate. "A lot of the cells regulated by your body's clock are located in the lining of your gut. If somebody participates in shift work and their clocks have to constantly adjust, the genes that are supposed to keep cells growing normally may not be activated at the right time, and repair doesn't occur," she says. That could lead to increased rates of colon cancer and other gastrointestinal problems such as ulcerative colitis, celiac disease, and Crohn's disease.

If you are a shift worker, here are a few ways to keep your work from making you sick:

•  Keep it regular. Stick with one shift, if that's possible. Rotating shift workers are the most likely to suffer long-term, says Dr. Hoogerwerf. "It's definitely clear that going back and forth between shifts is not good for the body," she says. And, she adds, "as boring as it sounds, living a regular, routine-driven lifestyle is going to be better for your overall well-being." That includes going to bed and getting up at the same time and eating at the same time every day, even if that means breakfast is at 8 p.m. and dinner is at 7 a.m. She adds that eating your biggest meal in the middle of the day helps, as well.

•  Try melatonin supplements. Dr. Hoogerwerf notes that a few studies have found melatonin to be effective in treating IBS symptoms, because it helps regulate your body's internal clock. The studies testing the supplement used doses in the 3-milligram range, which are available at any local health-food store. Be sure to buy products certified by U.S. Pharmacopeia,, or the National Sanitation Foundation (NSF) to ensure you're getting the dose advertised and no other sketchy supplement ingredients.