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What You Should Know About IBS-D

Written by Dr. Ruscio on December 10, 2020

Written by Dr. Ruscio on December 10, 2020 — Reviewed by Aimee Gallo

A Guide to Understanding IBS-D and Its Treatment

• What Is IBS-D|
• IBS-D Causes|
• IBS-D Treatment Plan|
• IBS-D Diagnosis|
• Bottom Line|

Irritable bowel syndrome (IBS) is a common diagnosis given to people with chronic, otherwise unexplained abdominal pain, irregular bowel movements, and a host of other possible symptoms [1]. Some people with IBS have diarrhea as a prominent feature and belong to an IBS subcategory called IBS-diarrhea, or IBS-D for short.

Needless to say, IBS-D can put a significant damper on your quality of life [2].

Although no cure currently exists for IBS-D, mounting evidence shows that lifestyle approaches may improve the condition and your quality of life. Such approaches may include eating a non-inflammatory diet, taking supplements to support digestion, reducing stress, correcting gut microbial imbalances, and making sure the bowels move regularly.

What Is IBS-D?

IBS-D is a subtype of IBS, which is a functional gastrointestinal disorder, or FGID [1]. In FGIDs, the digestive tract stops doing its job properly, but not because of any structural issues or biochemical irregularities that can be detected in x-rays, blood tests, or microscopic views of the intestine [3]. The Rome Foundation, which supplies doctors with a list of criteria to help them diagnose IBS, characterizes FGIDs as gut-brain axis disorders with the following [4]:

• Disturbed motility (muscular activity of the intestines)
• Hypersensitive GI tract nerves
• Abnormal functioning of the gut lining or immune system
• Imbalances in gut microbiota
• Impaired central nervous system communication

Estimates suggest that 10% to 12% of people in the United States have IBS, and females are three times as likely as males to have an IBS diagnosis [1].

About one-third of IBS sufferers have IBS-D, which means at least 25% of bowel movements appear as loose stools that are mushy without clear edges or completely liquid [1]. Another third of IBS sufferers have IBS with constipation — IBS-C — indicated when 25% of bowel movements have hard or sausage-shaped stools that are lumpy. A final third of IBS patients have IBS-M, or mixed IBS, in which at least 25% of bowel movements reflect diarrhea or constipation [1].

Symptoms of IBS-D

Typically, IBS-D symptoms include sporadic abdominal pain or cramping and chronic diarrhea. IBS-D sufferers may also experience any of the following [1]:

• Abdominal bloating after meals or with stress
• Feeling more full than makes sense
• Dyspepsia or indigestion: burning sensations in the upper abdomen, often along with bloating, belching, and nausea
• Mood disorders: emotions or moods that are inconsistent with the current situation and disrupt normal daily functioning and relationships
• Chronic migraines: having headaches on at least 15 days per month with migraines on at least eight of those days for at least three months in a row
• Interstitial cystitis: inflammation of the bladder that causes bladder or pelvic pressure and pain
• Fibromyalgia: widespread muscle or joint pain, often with fatigue and disruptions in sleep, memory, and mood
• Rarely, the sensation of incomplete or insufficient bowel movements; constipation may occur periodically in IBS-D

What Causes IBS-D?

Although the exact cause of IBS-D is unclear, research points to these possible underlying factors:

1. Dysbiosis or small intestinal bacterial overgrowth (SIBO): more than one-third of IBS patients may have SIBO [1, 5, 6, 7, 8, 9].
2. Gut infection: changes brought about by an immune attack on disease-causing microorganisms may disrupt intestinal motility even after the infection is cleared [1, 8].
3. Gut inflammation (gastroenteritis): a higher concentration of inflammatory cells, such as mast cells, cytokines, and eosinophils, may affect the nervous system and impair gut function [1, 10].
4. Food sensitivity: reactions to foods, such as FODMAPs [11], gluten [12], dairy products [13], and yeast [14] may irritate the gut lining, impairing motility and setting off immune reactions.
5. Malabsorption of bile acids: if bile acid from the gallbladder is not properly absorbed in the upper small intestine, it may flow into the large intestine and cause diarrhea-predominant IBS [1]; nearly 25% of IBS-D patients may have bile acid diarrhea of unknown cause [15].

People with IBS-D may be more likely to have a disorder called exocrine pancreatic insufficiency (EPI), in which the enzymes the pancreas produces to digest food are too few or otherwise unable to help with normal digestion. One study found that roughly 6% of people with IBS-D had EPI [16]. At this point, the jury is out on whether EPI can be considered a cause of IBS or vice-versa, but it’s worth asking your doctor about it just to be sure.

How To Treat IBS-D

The optimal treatment plan for IBS-D consists of these steps:

1. Eat a healthier diet.
2. If IBS-D symptoms persist, eat a low-FODMAP diet.
3. Support digestion.
4. Reduce stress.
5. Correct microbial imbalances.
6. Normalize (slow down) gut motility.

1. Eat a Healthier Diet

Frequently, just by making simple changes to the diet, people have seen significant improvements in their IBS-D symptoms [17]. First-line dietary changes include reducing your intake of sugar, processed foods, alcohol, and caffeine, and increasing the amount of fruits and vegetables in your diet.

2. Eat a Low-FODMAP Diet

If the first-line dietary changes don’t seem to improve your IBS-D symptoms after a couple of weeks, the next thing to try is a low-FODMAP diet. The acronym FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols that occur in specific foods. These sugars and starches can feed gut dysbiosis, making high-FODMAP foods hard for IBS patients to digest and irritating to the gut lining. Clinical trials have found that a low-FODMAP diet improved GI symptoms and stool consistency and frequency, as well as the quality of life, anxiety, and work productivity, in people with IBS-D [18, 19, 20].

3. Support Digestion

If you’re still not seeing improvements to your IBS-D symptoms, certain supplements may give your gut the boost it needs. Probiotics, immunoglobulins, and digestive enzymes may give your digestive system a hand at breaking down food and absorbing nutrients.

• Probiotics: Although some conflicting studies exist [21], probiotics in clinical trials have largely improved IBS-D symptoms, including diarrhea [22, 23, 24, 25, 26].
• Serum-derived bovine immunoglobulins appear to be safe and effective at reducing symptoms in IBS-D, including diarrhea [27].
• If EPI appears to be an issue, pancreatic enzyme replacement therapy (called PERT for short), a doctor-prescribed treatment for EPI, may be helpful [16].

4. Reduce Stress

Stress is a pretty regular part of most people’s lives and a likely contributor to your IBS-D symptoms. Several types of evidence-based practices have shown positive effects at reducing stress and specifically improving life for IBS patients.

• Breathwork or meditation can lower stress and may improve digestion.
• Moderate exercise can reduce stress and may have important benefits to IBS patients [28].
• Psychological support. In people with moderate to severe IBS-D, working with therapists who offered cognitive-behavioral therapy (CBT) or mindfulness-based stress reduction (MBSR), helped improve their quality of life [2].
• Hypnotherapy. Gut-focused hypnotherapy may help reduce IBS symptoms and improve quality of life [29], even when done via online video [30].

5. Correct Microbial Imbalances

If the previous approaches don’t seem to help, SIBO or other types of dysbiosis may be part of the picture. Probiotic therapy is my first choice for treating dysbiosis, but for those who don’t respond to probiotics, herbal antimicrobials or prescription antibiotics may be warranted.

• Probiotics. Although many believe that probiotics should not be used in cases of SIBO or dysbiosis, research clearly refutes this idea [31]. Clinical trials have shown probiotics to reduce SIBO [31, 32, 33] and other infections, such as H. pylori [34], parasites [35], and fungi [36, 37].
• Herbal antimicrobials. Although fewer studies exist for herbal antimicrobial treatments for IBS and SIBO, herbal preparations may be as effective as prescription antibiotics at treating both [38, 39]. Berberine, in particular, has reduced the frequency of diarrhea, abdominal pain, and urgency, as well as improved quality of life in IBS-D patients [38, 40].
• Rifaximin. With the brand name Xifaxan, this FDA-approved intestine-specific antibiotic may help modulate gut microbiota, inflammation, hypersensitivity, and intestinal permeability [41, 42].

6. Normalize (Slow Down) Gut Motility

Diarrhea happens when gut motility is too fast. Diarrhea causes dehydration and malabsorption, both of which can become serious issues if diarrhea becomes chronic. If IBS-related diarrhea persists after consistently applying dietary changes, digestive supports, stress reduction practices, and microbial balancing, the following conventional medications may be helpful.

• Loperamide. Brand name Imodium, this over-the-counter anti-diarrheal may help slow motility temporarily, but few clinical trials have researched its use in IBS [42].

• Eluxadoline. With the brand name Viberzi, this FDA-approved prescription drug targets opioid receptors in the digestive tract to slow motility, reduce water entering the intestine, and decrease pain perception [41, 42].
• Alosetron. With the brand name Lotronex, this FDA-approved prescription drug modulates nerve signals and slows motility [41, 42].

Peppermint oil is an herbal supplement that may relax the smooth muscles in the digestive tract, helping to decrease pain, bloating, and bowel movement urgency. But it commonly produces side effects, including heartburn or indigestion [42], so test it carefully.

If your doctor finds your stool has high levels of steatocrit, bile acid malabsorption (BAM) is likely causing your chronic diarrhea. Conventional medications that can help address this include bile acid binders [42], such as:

• Cholestyramine (Locholest)
• Colestipol (Colestid)
• Colesevelam (WelChol)

Important Notes About Medication:

• The FDA considers drugs as a bottom-of-the-list option for IBS, to be considered only if lifestyle changes don’t help [43].
• Dicyclomine: With the brand name Bentyl, this is another prescription drug that has been used to treat pain in IBS-D, but the FDA does not recommend using it because of side effects, including fatigue, dizziness, dry eyes, and dry mouth [42].

How Is IBS-D Diagnosed?

I recommend working with a gut specialist to find out whether you have IBS-D. As is true for all IBS subtypes, doctors have no clear path to diagnosing IBS-D. Without specific blood tests or other diagnostic panels to indicate IBS-D, primary care doctors and gastroenterologists typically have to first rule out conditions caused by structural or biochemical problems, including [44]:

• Celiac disease
• Inflammatory bowel disease (IBD)
• Colon cancer
• Chronic GI infections
• Microscopic colitis
• Primary bile acid diarrhea

If general blood tests, various breath tests, or colonoscopies don’t indicate these conditions, doctors may then use a set of questions, called the Rome IV criteria, combined with your health and family histories to decide whether you likely suffer from IBS-D [45].

Final Thoughts on IBS-D

IBS-D is simply a subtype of IBS that has diarrhea as a prominent symptom. It’s possible to switch back and forth between IBS-D and IBS-C, putting you in the mixed-type — or IBS-M — a category of people who suffer from IBS. In any case, the label is not as important as your symptoms and how they affect your life.

The good news is that when the right supports are in place, people can and do shift to a symptom-free existence and a higher quality of life. Until then, when IBS-D is part of your day-to-day life, this article can be your guide to finding appropriate care and giving your body the special support it needs.