What is Irritable Bowel Syndrome
Irritable bowel syndrome, or IBS, is a gastrointestinal disorder that affects up to 20% of the population of the USA and is associated with an alteration in bowel habits (such as diarrhea and constipation). Patients with IBS have a considerably impaired quality of life. IBS is more prevalent in women. IBS is a multifactorial disorder and is still incompletely understood. These are some of the factors that have been implicated in the development of IBS, specifically in women:
Genetics. A recent study performed a sex-stratified genetic analysis and showed that certain variants on chromosome 9 increase the risk of IBS only in women and are associated with constipation-predominant IBS in women as well as harder stools in women. This highlights the importance of a genetic predisposition to developing irritable bowel syndrome.
Female hormones. A recent study comparing male and female mice showed that female mice exhibited higher levels of distress, lower body temperature, and higher blood histamine levels in response to stress stimulation. Female responses to stress were more exaggerated in this animal model. These data suggest that biological sex may play a prominent role in the prevalence and severity of IBS.
Visceral hypersensitivity. A subset of patients who have IBS, varying from 30% to 40%, are reported to exhibit enhanced sensitivity to distension of the colon. These people may have a reduced threshold for pain and an increased intensity of sensations. Multiple studies have shown that female hormones appear to influence visceral hypersensitivity. Visceral hypersensitivity could account for symptoms of urgency for bowel movements, bloating and abdominal pain experienced by patients.
Gut infections. Infection of the colon may disturb equilibrium in the gut. Changes in the gut may persist long after resolution of the infection. For example, IBS symptoms may develop in up to 25% of patients after Salmonella infection. Although severe symptoms typically disappear within several weeks, bloating, diarrhea and abdominal discomfort may not. Although the exact mechanisms underlying postinfectious IBS are not clearly understood, increased intestinal permeability has been reported in these patients. Increased intestinal permeability seems to correlate with several other clinical conditions, including food allergies, IBD, rheumatoid arthritis, allergic disorders, celiac disease and a few chronic dermatological conditions.
Diet and IBS
A recent study revealed that a “western dietary pattern” which was defined as consumption as fatty and sugary products and snacks, was correlated with a moderately increased risk of developing irritable bowel syndrome.
A diet low in fermentable oligo, di and monosaccharides and polyols (FODMAP diet) improves quality of life and reduces activity impairment in women with irritable bowel syndrome and diarrhea.
A recent randomized controlled trial showed that a diet low in fermentable oligo, di and monosaccharides and polyols (FODMAP diet) reduces anxiety in women with irritable bowel syndrome and diarrhea.
Exercise and IBS
Low to moderate intensity aerobic exercise training modulates irritable bowel symptoms by reducing measurable markers of inflammation and oxidative stress.
Endometriosis and IBS
Women with endometriosis have a higher prevalence of symptoms consistent with irritable bowel syndrome.
A recent study reveals an association between estrogen receptors and irritable bowel symptoms. Therefore, immunological dysregulation observed in women with irritable bowel syndrome may involve estrogen-dependent pathways.
Bowel symptoms may be exacerbated by menstruation and concurrent diagnosis of endometriosis.