Irritable bowel syndrome (IBS)—also referred to as spastic colon, mucous colitis, spastic colitis, nervous stomach, and irritable colon—affects nearly 20% of the adult population. It is a multifaceted functional disorder without any discrete structural abnormality or biochemical or organic cause. It occurs more frequently in women (14–24%) than in men (5–19%) and typically presents before 35 years of age. It is not life-threatening and does not contribute to the development of inflammatory bowel disease or cancer.
Approximately 70% of those presenting symptoms associated with IBS do not seek medical attention. The predominant symptom is abdominal pain, bloating, and gastrointestinal discomfort, which may be relieved with bowel movements. Symptoms are idiosyncratic, ranging from constipation or infrequent bowel movements to diarrhea. Some individuals have episodes of constipation and diarrhea, with intervening periods of GI quiescence.
Many theories for the causes of IBS have been advanced, leading to a variety of therapeutic approaches. Some research suggests IBS is predominately a colon motility disorder, or an illness associated with the secretion of the neurotransmitter serotonin, which is frequently elevated among individuals with a stressful lifestyle. GI infection may make the intestine more reactive to mild stimulation or stress. The problem is so vexing that fringe and sometimes harmful alternative approaches have blossomed into big business.
IBS symptoms are frequently exacerbated by large meals, colon bloating, certain medications (e.g., antibiotics), some foods (e.g., grains, dairy, or alcohol), caffeinated beverages, physical or emotional stress, and level of physical exercise. Some research suggests that women may experience increased symptoms during their menstrual periods, implying that reproductive hormones may play a role.
Standard management of IBS includes dietary and drug intervention. Most individuals with IBS can benefit from gradual increased intake of dietary fiber and water intake, consumption of 3–6 low-fat meals, minimal intake of alcoholic and caffeinated beverages, and gradually restricted intake of fructose and sorbitol or lactulose (if chronic constipation is a problem).
There is some evidence that microbial overgrowth, particularly in the small bowel, may be resolved through increased use of some strains of probiotics that modulate inflammatory responses and promote digestion of dietary components such as lactose and fiber. Reports of dramatic and apparently enduring clinical responses to probiotics have been thrown into question and have frustrated patients and clinicians because of the huge and growing spectrum of commercially available organisms. Quality and quantity may vary significantly depending on strain, manufacturer, age, packaging, recommended dose, and whether the probiotic matrix consists of single or multiple organisms, with or without a fructooligosaccharide substrate.
Peppermint oil and peppermint tea are traditional medicines that contain an array of phenolic constituents, may relax the GI tract (slow motility), and exert local analgesic and anesthetic effects. Human clinical studies that support the animal studies and traditional use of peppermint in treating IBS are limited. Some animal studies and traditional use indicate that the sedative Salvinorin A, a neoclerodane from Mexican mint, has had some success in managing IBS-associated pain.
Available are medications that regulate motility and promote restoration of normal bowel contraction (Dicetel, Modulon, Zelnorm); antidiarrheal drugs aimed at preventing cramps (Immodium, Lomotil, Levsin, Bentylol) and controlling stool frequency; digestive enzymes (Cotazyme, Creon, Pancrease, Ultrase) intended to relieve symptoms by facilitating digestion in the small intestine, especially if pancreatic insufficiency is contributing to the symptoms; analgesics that increase pain threshold; and possibly selective serotonin reuptake inhibitors (Prozac, Paxil, Zoloft). In some cases, tricyclic antidepressants (Amitril, Norpramin) and psychological therapy are components of the treatment strategy.
Continuous research will enhance our understanding of the disease process, and strict adherence to dietary regimens and medication therapies will result in significant improvement. The development of medical foods now provides another form of dietary support for IBS patients. The appearance of cultured milk products enriched with proprietary strains of probiotic organisms designed in the laboratory to "regulate" disordered bowel function may well mark the arrival of a new and important era in the production and marketing of foods with potent clinical applications.
by Roger Clemens, Dr.P.H.,
Director, Analytical Research, Professor, Molecular Pharmacology & Toxicology, USC School of Pharmacy, Los Angeles, Calif.
by Peter Pressman, M.D.,
Attending Staff, Internal Medicine, Cedars-Sinai Medical Center, Los Angeles, Calif.