There's some evidence that chocolate can cause constipation, though other studies show chocolate may actually help some people, Dr. Park says.
In one 2005 study, people with chronic constipation or irritable bowel syndrome were more likely than people without those problems to say that chocolate caused constipation (as did bananas and black tea).
Eliminate or cut back on chocolate if you think it could be causing your constipation.
Painkillers, specifically narcotics, can cause constipation.
"A lot of receptors for the narcotic class of drugs are in the digestive tract, so it tends to bring everything to a halt," says Dr. Thomas Park, a gastroenterologist with the University of Rochester Medical Center Park in New York. "In general, it's a good idea for everyone who's placed on one of these drugs to also place them on a gentle laxative like a stool softener."
Some studies (but not all) have suggested that there might be a higher risk of constipation for people who are chronic users of pain relievers like aspirin and ibuprofen.
Vitamins in general won't cause constipation, but certain components, such as calcium and iron, can be a problem.
"I would tell a patient to stop taking the iron [or calcium] unless they really need it and, if they do need it, I would put them on a stool softener to counteract that," says Dr. Ginsburg, who is a spokesperson for the American Gastroenterological Association.
A diet high in cheese and other low-fiber/high-fat foods such as eggs and meat can slow down your digestion. The obvious solution? Cut down on your intake of such foods, and increase fiber intake to 20 to 35 grams a day.
"If you're going to have cheeses and red meat and eggs, mix in some salads or other foods that have fiber," Dr. Park advises. And avoid fast foods and processed foods, which are generally low in fiber.
Hypothyroidism, or an underactive thyroid gland, slows the body's metabolic processes - even the gut.
Not everyone with an underactive thyroid has constipation, nor do all cases of constipation mean that the butterfly-shaped gland in your neck is underperforming.
Still, "when I see a young person who's constipated more than normal and really complaining, I do tend to get a thyroid level," says Dr. Carla H. Ginsburg, assistant professor of medicine at Harvard Medical School in Boston.
Inflammatory bowel disease (IBD) includes two chronic conditions - Crohn's disease and ulcerative colitis. Both can cause cramping, weight loss, bloody stools, and other health problems.
Chronic diarrhea is a common symptom of both. However constipation can be a problem too.
In ulcerative colitis, constipation can be a sign of inflammation in the rectum and in Crohn's disease it can be a sign of an obstruction in the small intestine. However if you have constipation alone, without other symptoms, it's unlikely to be due to IBD.
Diabetes can cause nerve damage that can affect a person's ability to digest food, says Dr. Park.
Most people with advanced diabetes know they have it. Still, it's reasonable to do a blood sugar test on someone who is regularly constipated, says Dr. Ginsburg.
Neurological conditions such as multiple sclerosis or Parkinson's disease can cause constipation. Usually, though, "this goes with another symptom such as trouble urinating, double vision, or a gait problem," Dr. Ginsburg says.