July 2016 Issue
Digestive Wellness: Get Things Moving — A Dietitian's Guide to Relieving Constipation
By Kate Scarlata, RDN
Vol. 18 No. 7 P. 10
When the human internal plumbing slows down, constipation presents with infrequent passing of stool; hard, dry stool; and/or a sense of incomplete emptying. Chronic constipation is a massive clinical problem, occurring in about one in five people globally, and accounts for at least 8 million annual visits to US health care providers.1
Chronic idiopathic constipation (CIC) and the irritable bowel subtype constipation-predominant irritable bowel syndrome (IBS-C) are the two primary forms of chronic constipation. IBS is a debilitating, painful gastrointestinal (GI) disorder prevalent in 10% to 15% of North Americans. IBS-C accounts for about 5% of those who suffer with this condition.2
Although typically classified as different diseases, IBS-C and CIC symptoms (gas, bloating, straining with elimination, and hard stools) frequently overlap and disrupt quality of life. The main differentiator is that pain often is present with IBS-C. "Constipation often flies under the radar in terms of its effect on patients. It's certainly not a topic that people want to speak about. Yet, constipation can have a profound impact on the patient's well-being and ability to function," says William Chey, MD, a professor of gastroenterology at the University of Michigan. "People often think that diarrhea is more impactful to patients than constipation. Actually, I would argue the opposite. Diarrhea is a huge problem when it causes a person to feel the urge to move their bowels and when they're passing diarrhea. On the other hand, constipation makes people feel ill all of the time—complaints like abdominal pain, bloating, gas, feeling like you have to go but can't are present all day and all night long."
Contributors to Constipation
Constipation may occur as a secondary systemic effect via motility disturbances in diabetes and hypothyroidism and neurologic effects in Parkinson's disease, spinal cord disorders, and stroke. Various medications, including calcium antagonists for high blood pressure and opioids for chronic pain, are linked with constipating side effects.3
Alterations in the gut microbiota also play a role. Gas produced as microbial fermentation end products can alter bowel movements. Elevations in methane and hydrogen gas are associated with slow or rapid transit of the intestine, respectively.4 "Methane is a gas produced by particular bugs in the gut, and the methane gas itself can slow down the intestinal movements," says Mark Pimentel, MD, director of the gastrointestinal motility program and laboratory at Cedars-Sinai Medical Center in Los Angeles. "We know that the more methane produced, the more constipated the person is. It's now known that getting rid of methane with antibiotics improves constipation in IBS."
Rather than eradicate the microbes that produce methane via antibiotics, novel medication trials are under way to assess the benefit of simply restricting the production of methane via microbial fermentation. In addition, defecation disorders such as dyssynergic defecation, which occurs when the muscles of the rectum contract rather than relax during a bowel movement, can be a cause of incomplete emptying. Treatments for defecation disorders include biofeedback and physical therapy.
Constipation Tool Box
Dietary strategies to aid the constipated patient include increasing selective fiber sources and fluid intake; eating three meals per day; a trial of the low-FODMAP (fermentable oligo-di-monosaccharides and polyols) diet, which is reduced in certain fermentable short-chain carbohydrates; and/or a trial of probiotics. Regular physical activity also can promote bowel motility. The low-FODMAP diet is an evidenced-based dietary approach to managing symptoms of IBS, which includes a constipation subtype. It's a three-part elimination diet; in the initial phase, high-FODMAP foods are removed from the diet in an effort to calm GI symptoms. The second phase involves a methodical reintroduction of FODMAPs back into the diet to help identify which FODMAPs trigger symptoms. The third phase is a less-modified low-FODMAP diet. The goal of this long-term phase is to manage symptoms while liberalizing the diet as much as possible without exacerbating GI distress. The diet has been shown to manage symptoms in 70% to 75% of those who suffer from IBS.5
The following are several tips dietitians can suggest to patients suffering from constipation:
• Hydrate. Consuming adequate fluid is a modifiable factor that may improve constipation.6 Encourage fluids at every meal and while in transit to and from work, school, or other activities.
• Eat regularly. Eating induces the gastro-colic reflux, stimulating intestinal movements that may relieve constipation.
• Up the fiber. Increasing intake of a variety of different fibers offers health benefits such as bulking stool, hastening transit time, and feeding healthful probiotic gut bacteria. Psyllium husk as a fiber supplement has some of the best evidence to support its use.7 Partially hydrolyzed guar gum (PHGG), a water-soluble fiber with prebiotic activity, also has some of the best research supporting its use to relieve constipation, as it improves transit time and stool consistency and stimulates growth of beneficial gut microbes, such as Bifidobacteria and butyrate-producing flora.8,9
• Add exercise. Walking and other types of exercise that add weight-bearing, jarring movements to the body may stimulate motility.
• Listen to the body. Patients should be encouraged to listen to their body when the urge to move the bowels occurs rather than waiting until later. Water is reabsorbed in the colon, and the longer the stool remains, the drier or more difficult it will be to pass.
• Get cultured. Probiotics may minimize constipation, though the exact mechanism is unknown. Probiotics with the best evidence for helping manage constipation are Bifidobacterium infantis 35624, VSL#3, and B animalis.10,11 Because probiotic science is complex and still in its infancy, more compelling research demonstrating effective probiotic strains, dosing, and therapy duration is needed.
• Reduce fermentable carbohydrates. Trying a low-FODMAP diet may help IBS-C patients, reducing pain, gas production, bloating, and perhaps improving stool consistency.5
Primer on Fiber
Fiber generally is defined as a carbohydrate that isn't hydrolyzed or absorbed in the upper part of the GI tract. Fiber comes in many shapes and forms, varying in water solubility, fermentability, and degree of polymerization. When it comes to digestive benefits, soluble fiber—found in oats, chia seeds, and beans—softens stool by creating a gellike consistency, acting as a bulking agent. Different sources of soluble fiber can impact gas production in the colon and—depending on the fiber's chain length—contribute to GI symptoms of bloating and excessive gas. Insoluble fiber, such as that found in fruit and vegetable skins, is poorly fermented (less gas production) and hastens transit time. However, few studies have been carefully executed in IBS patients to demonstrate its impact on constipation.
Because of the nature of gut flora and the gut's sensitivity to luminal distention—as an end product of gas production—tolerance to fiber depends on the individual. Many people can tolerate a mix of fiber to maximize its many health benefits, including normal cholesterol and blood sugar levels, and maintaining a healthy weight. IBS patients may be more sensitive to the intestinal stretching that occurs when copious amounts of gas are produced via microbial fermentation of fiber. However, selecting fibers associated with less gas production may be better tolerated.
Psyllium and oat fibers, soluble fibers that can contribute to moderate gas production, have a good laxative effect and hasten transit time. And they may be considered one of the best options to relieve constipation, particularly in those with IBS-C.7 PHGG is a regulating soluble fiber that has a very slow fermentation rate, therefore resulting in significantly less gas and bloating associated with some soluble fibers.12,13 Similar to psyllium, oat fiber, and inulin, PHGG helps relieve constipation, but unlike most soluble fibers, PHGG won't lead to diarrhea but will return stool content to normal from a diarrheal state.14 In addition, PHGG was found to normalize bowel habits not only for constipation but also in patients with IBS-C and diarrhea-predominant IBS.14
Insoluble, nongas-producing fiber supplements that appear well tolerated include cellulose and methylcellulose. Constipation sufferers routinely are encouraged to boost their fiber intake to speed transit time.
Low-FODMAP Diets and Constipation
Fermentable oligosaccharides are short-chain fibers, also known as FODMAP subtypes fructans (found in wheat, onion, and garlic) and galacto-oligosaccharides (found in legumes). Their small size and solubility means fructans and galacto-oligosaccharides fibers are rapidly fermented in the terminal ileum, resulting in production of large amounts of gas.
According to a 2014 study in Gastroenterology, a reduction in dietary FODMAPs, which restricts certain short-chain sugars and fibers, improves symptoms in IBS patients, including both constipation and diarrhea predominant subtypes.5 Lead researcher Emma Halmos, PhD, a postdoctorate nutrition researcher at The Walter and Eliza Hall Institute of Medical Research, the oldest research institute in Australia, says, "My study was not powered to look at individual subgroups of IBS, but it was interesting that IBS subjects from all four subgroups saw benefit from the low-FODMAP diet, including self-rated 'satisfaction of stool consistency.' As FODMAPs are both gas producing and osmotically active, it is expected that patients with abdominal pain and diarrhea would improve. Those with constipation also improved. This may be attributed to a reduction in colonic gas, luminal distension, and perhaps subsequently improved motility beyond the disadvantage of reducing natural laxative effect."
The low-FODMAP diet is best guided by a knowledgeable dietitian.2
Improving the Exit Strategy
If dietary interventions offer only partial improvement in constipated patients, further evaluation with the patient's primary care physician or gastroenterologist may be warranted. Contributing problems include defecation disorder (which may benefit from physical therapy and biofeedback), small intestinal bacterial overgrowth—particularly with elevations in methane gas (which may warrant antibiotic treatment)—and medication side effects (which may warrant further evaluation and modification).
In some cases, laxatives containing chemical stimulants to improve motility may be necessary. In more severe cases, prescription medications, such as linaclotide and lubiprostone, which have both osmotic and prokinetic effects in the colon, may be initiated.
— Kate Scarlata, RDN, is a Massachusetts-based dietitian and digestive health expert. She has a consulting relationship with Nestlé Nutrition Health Science in Florham Park, New Jersey.
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12. Ohashi Y, Harada K, Tokunaga M, et al. Faecal fermentation of partially hydrolyzed guar gum. J Funct Foods. 2012;4(1):398-402.
13. Niv E, Halak A, Tiommy E, et al. Randomized clinical study: partially hydrolyzed guar gum (PHGG) versus placebo in the treatment of patients with irritable bowel syndrome. Nutr Metab. 2016;13:10. doi: 10.1186/s12986-016-0070-5.
14. Quartarone G. Role of PHGG as a dietary fiber: a review article. Minerva Gastroenterol Dietol. 2013;59(4):329-340.
William Chey, MD, has consulting relationships with Ardelyx in Freemont, California; AstraZeneca in London, UK; Allergan in Parsippany, New Jersey; Ironwood Pharmaceuticals in Cambridge, Massachusetts; Sucampo Pharmaceuticals in Rockland, Maryland; and Takeda in Osaka, Japan.