Constipation-Predominant Irritable Bowel Syndrome (IBS-C)
Constipation-predominant irritable bowel syndrome (IBS-C) is a subtype of irritable bowel syndrome (IBS) that leads to abdominal pain, bloating, and straining. The exact causes are unknown, but research suggests that multiple factors — such as the gut-brain axis, abnormal muscular contractions, gut microbes, and genetics — could play a role in the disease. IBS-C can be managed with dietary modifications, supplements, and prescription medications.
IBS-C is a subtype of IBS characterized by abdominal pain, bloating, and straining to pass stool. Approximately one-third of IBS sufferers have IBS-C, and women are much more likely than men to fit the criteria of IBS-C. IBS-C is associated with anxiety, but unlike IBS-D, it isn’t linked to depression.
IBS-C shares some symptoms — including abdominal pain and bloating — with the other IBS subtypes, but in IBS-C, constipation is the most common bowel habit, and people with IBS-C also often report straining to pass stool. Symptoms often temporarily subside after a bowel movement.
There is no test to diagnose IBS-C, so doctors often use blood and stool tests to rule out other diseases before reaching an IBS-C diagnosis. Rome IV criteria can be used to diagnose IBS-C based on the proportion of bowel movements rated as constipation compared to those rated as normal. Symptoms need to occur at least once per week for at least three months to be considered IBS.
Medications for IBS-C include osmotic laxatives and guanylate cyclase-c agonists, both of which can increase water retention in the bowel and stimulate intestinal motility. Antidepressants and antispasmodics may also be used to reduce abdominal pain.
There’s some evidence that methane could slow intestinal transit, and antibiotic treatment of methane-positive small-intestinal bacterial overgrowth (SIBO) improved constipation in a small number of studies.
A number of probiotic strains have been shown to reduce abdominal pain, bloating, and intestinal transit time while improving stool consistency. However, the effects appear to be temporary, with most benefits seen around six to eight weeks of supplementation even though some participants continued to take the probiotics for twelve weeks.
Doctors might also recommend over-the-counter fiber supplements if increasing dietary fiber doesn't help. Psyllium husk appears to be effective for normalizing stool in both IBS-C and IBS-D. Additionally, peppermint oil can ease IBS-associated abdominal pain.
One study found that a traditional Persian blend of herbal extracts had a laxative effect greater than placebo; interestingly, the British Pharmacopoeia simple syrup used to compound the blend, which served as placebo, itself also had a noticeable laxative effect. This could be due to the high concentration of sugar causing water retention in the intestine and easing stool transit.
Flixweed (Descurainia sophia), a common weed also known as tansy mustard, was as effective as figs for improving pain, distension, and bowel movement frequency.
Although a low-FODMAP diet isn’t recommended for IBS-C, some people with IBS-C report greater abdominal distension after eating foods high in FODMAPs. Dietary fiber is only weakly associated with bloating or distention after eating.
Both kiwis and dried, rehydrated figs have been shown to improve IBS-C symptoms at reasonable serving sizes of two kiwis per day or 45 grams of dried figs twice per day.
Electroacupuncture — a form of acupuncture that uses electrodes in place of needles — was more effective for constipation and abdominal pain relief compared to sham treatment in a four-week study, but participants were able to use a laxative if they had less than three bowel movements per week. Since the researchers didn’t disclose information about laxative use during the study, it’s unclear whether the improvements were due to the electroacupuncture or the laxative.
Although traditional Chinese medicine appears to be as effective as pharmaceutical drugs, most studies are of low quality with a high risk of bias due to a lack of blinding and participant randomization.
Though the cause of IBS-C is still unknown, research suggests that multiple factors — such as the gut-brain axis, abnormal muscular contractions, gut microbes, hormones, and genetics — could play a role in the disease. IBS is twice as common in women compared to men, which could be explained, in part, by hormonal changes during the menstrual cycle.
Some studies have found a higher prevalence of methane-positive small-intestinal bacterial overgrowth (SIBO) in people with IBS-C and other forms of constipation, suggesting that this form of SIBO could be linked to symptoms via excess methane production (which could slow intestinal transit.) However, it’s unclear whether methane production is a cause or consequence of slow transit.