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Functional Gastrointestinal Disorders and Nutrition

What are Functional Gastrointestinal Disorders?

Functional gastrointestinal disorders (FGIDs) are a group of disorders which are characterized by persistent and recurring GI symptoms as a result of abnormal functioning of the GI tract. They are not caused by structural or biochemical abnormalities, such as tumors and masses. Thus, many routine medical tests used to diagnose GI diseases, such as ultrasounds, endoscopies, and blood tests, will produce essentially normal results. They are also not considered psychiatric disorders, although stress and psychosocial difficulties can exacerbate symptoms. Examples of functional GI disorders include Irritable Bowel Syndrome (IBS), functional dyspepsia (pain or discomfort in the upper abdominal area, feelings of fullness), functional vomiting, functional abdominal pain, and functional constipation or diarrhea. An estimated 25 million Americans have functional GI disorders, although 50-80% of people do not consult a physician for their symptoms despite reporting significant job absenteeism and lower productivity. For example, it has been reported that IBS is the second leading cause of missed workdays or school after the common cold.

FGIDs are characterized by three primary features – motility, sensation, and brain-gut dysfunction. Motility refers to the muscular activity of the GI tract. Normal motility is characterized by a sequence of muscular spasms from top to bottom, called peristalsis. In FGIDs, the muscular spasms which impact motility can be very rapid or slow and disorganized, sometimes causing pain. Sensation determines how the nerves of the GI tract respond to stimuli, such as digesting a meal. With FGIDs, the nerves may be especially sensitive that even normal muscular contractions in the GI tract may cause discomfort. Brain-gut dysfunction describes impairment of the communication between the GI system and the brain.


Unfortunately, routine tests used for diagnosis of common GI disorders are usually negative for most FGIDs. However, more research is being conducted to increase understanding of FGIDs. Experts have developed a set of symptom-based criteria called the “Rome Criteria” which is helpful for diagnosing FGIDs. However, gastroenterologists are encouraged to rule out other causes of GI discomfort, such as celiac disease, inflammatory bowel disease, and bowel obstruction. Because our understanding of these disorders is still developing and symptoms can vary between individuals, patients often feel discouraged when it comes to treatment.

The Role of Nutrition

Little is currently known about the effectiveness of diet therapy for the treatment of IBS and FGID symptoms. However, the single most important aspect to IBS/FGID nutrition therapy is that there is no single diet to help resolve symptoms. Individualization is key – everyone has different food and psychosocial triggers. The best advice is to look for patterns when GI symptoms develop and write it down in a food journal. Many dietitians, however, have had success with the use of elimination diets. Specifically, the Low FODMAP diet has proven invaluable. FODMAPS (fermentable oligosaccharides, disaccharides, and monosaccharides and polyols) are a group of short-chain carbohydrates found in many of the foods we eat. They share three characteristics which make them more likely to cause GI distress: they are poorly absorbed in the intestine, draw extra water into the intestines, and are rapidly fermented by bacteria in the bowel. The result is increased gassiness, bloating, abdominal pain, and diarrhea. During the elimination phase, the patient consumes only foods that contain little or few FODMAPS. Next, the patient challenges him/herself by reintroducing food groups in a systematic way, with the guidance of a Registered Dietitian. Signs and symptoms of GI distress should be tracked throughout this process. Few foods will require complete elimination from the diet completely in the long term.

Fiber is a controversial subject for individuals with FGIDs. The Academy of Nutrition and Dietetics recommends 25-30 g fiber per day with the addition of plenty of fluids. However, fiber is hit or miss for many people experiencing GI distress. Humans do not contain the enzymes to break down fiber. Therefore, it is not digested nor absorbed into the body, so it becomes a substrate for fermentation in the colon. This may cause increased gas and bloating. Fiber can be the answer for some people, especially those affected by constipation. However, fiber therapy doesn’t always work and can even make symptoms worse.

Probiotics are another controversial subject among those with GI issues. Several studies have been conducted to research the safety and efficacy of probiotics, and their role in improving symptoms and normalizing bowel movement frequencies for patients with chronic constipation or diarrhea related to IBS. A 2008 review article published in The Journal of the American Dietetic Association found that a probiotic known as Bifidobacterium infantis has been shown to be effective in treating IBS. However, it should not be used as a first-line defense in the treatment of IBS. Rather, it is important to get to the root cause of the issue, including food triggers, sensitivities, and psychosocial causes.

If you are experiencing gastrointestinal troubles, consider the following interventions:

  • First and foremost, get to the root cause – talk to your doctor and get tested!
  • Try an elimination diet under the guidance of a Registered Dietitian
  • Balance gut bacteria
  • Don’t overeat
  • Be mindful of what you are eating
  • Eliminate sugar alcohols
  • Slow down
  • Check vitamin levels at your next doctor’s appointment
  • Get enough sleep
  • Work on stress management
  • Get enough exercise (and not too much)
  • Eat “real” foods
  • Are you eating enough fiber?
  • Avoid common triggers: NSAIDs, acid blockers, alcohol
  • When you gotta go, you gotta go – don’t hold it in.


  1. https://www.med.unc.edu/ibs/files/educational-gi-handouts/What%20Is%20Functional%20GI.pdf
  2. http://www.todaysdietitian.com/newarchives/060109p34.shtml

By Jillian Klemm, Dietetic Intern

Wake Internal
Wake Gastroenterol
Wake Women's Health
Rx Urgent Care
Wake Research Associate
Wake Sport Medecine

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3100 Blue Ridge Rd, Suite 100 & 300

Raleigh, NC 27612

Phone: (919) 781-7500

Fax: (919) 645-3054

Monday - Friday: 8:00am - 5:00pm

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North Raleigh

10880 Durant Rd, Suite 100

Raleigh, NC 2.7614

Phone: (919) 781-7500

Fax: (919) 420-6065

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