The walls of the intestines are lined with layers of muscle that contract
and relax as they move food from your stomach through your intestinal tract to
the rectum. Normally, these muscles contract and relax in a coordinated rhythm.
But if you have IBS, the contractions are stronger and last longer than normal.
Food is forced through your intestines more quickly, causing gas, bloating and
diarrhea. In some cases, however, the opposite occurs. Food passage slows, and
stools become hard and dry.
No one knows exactly what causes IBS. Some researchers believe IBS is caused
by changes in the nerves that control sensation or muscle contractions in the
bowel. Others believe the central nervous system may affect the colon. And
because women are two to three times more likely than men to have IBS,
researchers believe that hormonal changes also play a role. Also, many women
find that signs and symptoms are worse during or around their menstrual
periods.
For reasons that still aren't clear, if you have IBS you probably react
strongly to stimuli that don't bother other people. Triggers for IBS can range
from gas or pressure on your intestines to certain foods, medications or
emotions. For instance, chocolate, milk and alcohol might cause constipation or
diarrhea. And the least bit of stress might send your colon into spasms.
If you're like most people with IBS, you probably find that your signs and
symptoms are worse or more frequent during stressful events, such as a change
in your daily routine or family arguments. But while stress may aggravate
symptoms, it doesn't cause them.
Sometimes another illness, such as an acute episode of infectious diarrhea
(gastroenteritis) can trigger IBS. Antibiotic use also may be a factor because
antibiotics disrupt the normal bacterial flora living in your bowel. Excessive
use of laxatives and even some antidiarrheal medications may contribute to the
problem as well.
If you experience cramping and bloating mainly
after eating dairy products or sugar-free gum or candies, the problem may not
be irritable bowel syndrome. Instead, your body may not be able to tolerate the
sugar (lactose) in dairy products or the artificial sweetener sorbitol.
