The full digest on four common causes of an upset stomach.
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Getty ImagesA bellyache has a long list of potential culprits—but stress is right up at the top. "Stress can affect every part of the digestive system," says Kenneth Koch, MD, chief of gastroenterology at Wake Forest Baptist Medical Center in Winston-Salem, N.C. It can ramp up acid production in the stomach or slow down digestion, inducing feelings of nausea and fullness. It can even change the consistency of your—well, you know. And sometimes, Dr. Koch says, it worsens the symptoms of an underlying problem. How do you know when abdominal discomfort stems from nerves or something else? For the good of your gut, here's a guide to some other usual suspects behind digestive trouble —and how to soothe your system.

Problem: You have white-hot pain in your chest.
It could be: Heartburn
The burning sensation is caused by acid from your stomach backing up into your esophagus. Certain foods and beverages can bring on the condition—such as tomato sauce, coffee and alcohol (which can relax your lower esophageal sphincter) and fatty fare (which may linger in your stomach). Stress and certain medications are often to blame, too. Proton pump inhibitors like Prevacid 24HR and Prilosec OTC offer relief by slowing acid production. But if your symptoms last more than three months, ask your doctor about prescription drugs.

Problem: You strain to go number two.
It could be: Constipation
"This can be an issue as women get into their late 30s and 40s," says Health's medical editor, Roshini Rajapaksa, MD, a gastroenterologist at NYU Langone Medical Center. "Women tend to become less active," she explains, which can lead to a sluggish gut. We also begin to experience hormonal changes that can cause hard, dry stools. (Blech.) "Drink four extra glasses of water a day and up your physical activity," suggests Dr. Rajapaksa. And make sure you're eating at least 25 grams of fiber daily. (A cup of cooked lentils, a bran muffin and a pear should do the trick.)

Problem: Your abdominal discomfort and altered BMs have lasted three months or more.
It could be: Irritable bowel syndrome (IBS)
Twice as many women as men suffer from IBS: "Women may have more bowel hypersensitivity, so nerves there overrespond to stimuli such as food or stress—causing increased gut activity," says Douglas Drossman, MD, professor emeritus of medicine and psychiatry at the University of North Carolina at Chapel Hill. The good news? About half of cases improve with dietary changes. Try avoiding trigger foods such as nuts, coffee and chocolate. Probiotics (in food or supplement form) could also help. If not, your doctor might prescribe medication.

Problem: Your belly feels like an inflated beach ball. Plus: cramps.
It could be: Nonceliac gluten sensitivity (NCGS)
Some people literally can't stomach gluten. But there is no conclusive explanation for NCGS and its range of symptoms, from gas and diarrhea to headaches, joint pain and more. Before you give up bread and pasta, get tested for a wheat allergy and celiac disease. Once they're ruled out, your doctor may suggest you go gluten-free to see if your symptoms improve.