3.  Celiac disease is an immune reaction to eating gluten, a protein found in wheat, barley and rye.  If you have celiac disease, eating gluten triggers an immune response in your small intestine, producing inflammation that damages the small intestine's lining and prevents absorption of some nutrients.  The intestinal damage can cause weight loss, bloating and sometimes diarrhea.  Eventually, your brain, nervous system, bones, liver and other organs can be deprived of vital nourishment.

5.  Lactose intolerance, is the inability to digest lactose, a sugar found in milk and milk-derived dairy products.  Lactose intolerant individuals have insufficient levels of an enzyme in their digestive system. In most cases this causes symptoms which may include abdominal bloating and cramps, flatulence, diarrhea, nausea, or vomiting after consuming significant amounts of lactose.

7.  GERD is a chronic digestive disease that occurs when stomach acid or, occasionally, bile flows back into your food pipe (esophagus).  Signs of GERD include acid reflux and heartburn. When these signs and symptoms occur at least twice each week or interfere with your daily life, doctors call this GERD.  People with GERD may need stronger medications, or even surgery, to reduce symptoms.

9.  Irritable bowel syndrome (IBS) is a common disorder that affects your large intestine (colon).  Irritable bowel syndrome commonly causes cramping, abdominal pain, bloating gas, diarrhea and constipation.  Most people with IBS find that symptoms improve as they learn to control their condition.  Despite these uncomfortable signs and symptoms, IBS doesn't cause permanent damage to your colon.

11.  Peptic ulcers are open sores that develop on the inside lining of your esophagus, stomach and the upper portion of your small intestine.  The most common symptom of a peptic ulcer is abdominal pain.  It's a myth that spicy foods or a stressful job can cause peptic ulcers. Doctors now know that a bacterial infection or some medications — not stress or diet — cause most peptic ulcers.

13.  Gallstones are hardened deposits of digestive fluid that can form in your gallbladder.  Gallstones range in size from as small as a grain of sand to as large as a golf ball.  Some people develop just one gallstone, while others develop many gallstones at the same time.  People who experience symptoms from their gallstones usually require gallbladder removal surgery.

15.  Ulcerative colitis (UC) is a disease that causes inflammation and sores, called ulcers, in the lining of the rectum and colon.  UC can happen at any age, but it usually starts between the ages of 15 and 30. It tends to run in families.  The most common symptoms are pain in the abdomen and blood or pus in diarrhea.  In severe cases, doctors must remove the colon.

17.  Diverticulosis is the formation of numerous tiny pockets, or diverticula, in the lining of the bowel.  The pockets can range from pea-size to much larger, are formed by increased pressure on weakened spots of the intestinal walls.  Diverticula can form while straining during a bowel movement, such as with constipation.  Diverticulitis occurs when there is inflammation and infection in one or more diverticula. This usually happens when the pockets become blocked with waste, allowing bacteria to build up, causing infection.  Symptoms include alternating diarrhea with constipation, painful cramps or tenderness in the lower abdomen, chills or fever.

19.  Dyspepsia (indigestion) is a common condition and usually describes a group of symptoms.  Symptoms can include belly pain or discomfort, bloating, feeling uncomfortably full after eating, nausea, loss of appetite, heartburn or burping up food or liquid (regurgitation).  Chocolate, mint, and alcohol can make dyspepsia worse, as can spicy foods, foods that have a lot of acid (like tomatoes and oranges), and coffee.  Treatment depends on what is causing the problem. If no specific cause is found, treatment focuses on relieving symptoms with medicine such as antacids or prescription drugs.