Fiber may not be the Holy Grail of good health as it has been reported to be, but who cares? In healthy individuals, the fermentation of fiber in the large intestine is generally considered normal and healthy.
Unfortunately, that’s not the case for many people with digestive problems. Consuming too much fiber can cause excess fermentation to spill over into the small intestine leading to a condition called Small Intestinal Bacterial Overgrowth (SIBO).
The small intestine normally contains drastically fewer and different bacteria than the large intestine. SIBO occurs when bacteria from the large intestine invade and multiply in the small intestine. There is a growing list of digestive conditions linked to SIBO including Gastroesophageal Reflux Disease (GERD) and irritable bowel syndrome (IBS). Not surprisingly, SIBO symptoms can include abdominal pain, bloating, distention, gas, acid reflux, cramps, diarrhea or constipation and even malnutrition.
Irritable Bowle Syndrom (IBS), SIBO and Fiber
Dr. Mark Pimentel and colleagues at Cedars-Sinai Medical Center in Los Angeles, CA, as well as Dr. John Hunter’s group at Addenbrooke’s Hospital NHS Trust, Cambridge, UK, have both published on the link between IBS, abnormal fermentation and SIBO. Hunter’s group linked fiber with abnormal gut fermentation and determined that a fiber-free diet could significantly reduce symptoms and intestinal gas.
Pimentel’s team determined that 78 percent of IBS patients had SIBO as indicated by a positive hydrogen breath test, an indirect measure or abnormal fermentation in the small intestine. Similar results were achieved in children. While some researchers achieved conflicting results, a meta-analysis of numerous studies validated the use of hydrogen breath testing for SIBO in IBS diagnostics. The most definitive results to date linking SIBO to IBS is a study of 320 subjects where 42 out of 62 people (67.7%) confirmed to have SIBO by direct bacterial culture method also had IBS.
GERD, SIBO and Fiber
There is a growing body of evidence that gastroesophageal reflux disease (GERD) is also caused by SIBO that includes the following:
- Reflux symptoms can be controlled by inhibiting gut bacteria with antibiotics,, or carbohydrate restriction,.
- GERD is associated with other conditions linked to SIBO such as IBS and cystic fibrosis,,.
- Intestinal gas and acid reflux can be induced with the prebiotic fructose oligosaccharide, which is indigestible by humans but fermentable by bacteria.
- SIBO has actually been detected in GERD patients, and the symptoms improved after antibiotic treatment.
Less is More
Fiber and often other hard-to-digest carbohydrates such as lactose, fructose, resistant starch and sugar alcohols comprise a unique type of food, and digesting it depends on cooperation between our bodies and our resident intestinal bacteria. While fiber consumption helps maintain our healthy gut bacteria, less is more.
Native or “good” bacteria have adapted to survival in the highly competitive environment of our gut by occupying unique niches based on their highly specialized abilities to break down and utilize a wide variety of fiber types.
A nutrient-limited environment (less fiber) helps rid our body of bad or pathogenic bacteria, such as C diff, because they are less able to compete when the going gets tough. A good analogy is leaving a few pieces of bread or bird seed in your back yard for the birds. If you overdue it, you can end up with rats. Clearly the health benefits of consuming large amounts of fiber are overstated and need to be balanced with the risk of digestive problems that can be caused or exacerbated by excess fiber.
Solution for GERD, IBS and SIBO
There are so many different kinds of fiber in so many different foods. It can be difficult to link digestive symptoms with any specific type of fiber. My advice would be to enjoy plenty of leafy green vegetables that contain less fermentable types of fiber. Nuts, seeds and berries are also good as long as you do not over do it. Be sure to limit legumes such as beans and lentils or avoid them all together if your symptoms are severe.
Controlling not only fiber but also other hard-to-digest carbohydrates in your diet will ensure that your gut microbes compete for the benefit of co-existing with you without overgrowing in the small intestine and producing symptom-causing gas. And the Fast Tract Diet gives you the means to do exactly that.
The Fast Tract Diet systematically measures how much of your food is feeding symptom-causing / gas-producing bacteria in your gut and gives you in “FP” points to control it. FP stands for Fermentation Potential. It’s a mathematical formula that gives you the points to create healthy balance in your gut. But don’t worry. The math is already done for you.
To learn more, read the Fast Tract Digestion Heartburn or IBS books and get the Fast Tract Diet mobile app. And join the Fast Tract Diet Discussion Group on Facebook for support, inspiration and discussion.
Need individualized help? Call us at (844) 495-1151 (US) to make an appointment.
Feel Better, Live long, Enjoy Life.
Read Part I and Part II on fiber.
 Dear KL, Elia M, Hunter JO. Do interventions which reduce colonic bacterial fermentation improve symptoms of irritable bowel syndrome? Dig Dis Sci. 2005 Apr;50(4):758-66.
 Pimentel M, Chow EJ, Lin HC. Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. Am J Gastroenterol. 2000;95:3503-6.
 Scarpellini E, Giorgio V, Gabrielli M, Lauritano EC, Pantanella A, Fundarò C, Gasbarrini A. Prevalence of small intestinal bacterial overgrowth in children with irritable bowel syndrome: a case-control study. J Pediatr. 2009 Sep;155(3):416-20.
 Bratten JR, Spanier J, Jones MP. Lactulose breath testing does not discriminate patients with irritable bowel syndrome from healthy controls. Am J Gastroenterol. 2008 Apr;103(4):958-63.
 Shah ED, Basseri RJ, Chong K, Pimentel M. Abnormal breath testing in IBS: a meta-analysis. Dig Dis Sci. 2010 Sep;55(9):2441-9.
 Pyleris E, Giamarellos-Bourboulis EJ, Tzivras D, Koussoulas V, Barbatzas C, Pimentel M. The prevalence of overgrowth by aerobic bacteria in the small intestine by small bowel culture: relationship with irritable bowel syndrome. Dig Dis Sci. 2012 May;57(5):1321-9. Epub 2012 Jan 20.
 Pennathur A, Tran A, Cioppi M, Fayad J, Sieren GL, Little AG. Erythromycin strengthens the defective lower esophageal sphincter in patients with gastroesophageal reflux disease. Am J Surg. 1994 Jan;167(1):169-173.
 Pehl C, Pfeiffer A, Wendl B, Stellwag B, Kaess H. Effect of erythromycin on postprandial gastroesophageal reflux in reflux esophagitis. Dis Esophagus. 1997 Jan;10(1):34-37.
 Mertens V, Blondeau K, Pauwels A, Farre R, Vanaudenaerde B, Vos R, Verleden G, Van Raemdonck DE, Dupont LJ, Sifrim D. Azithromycin reduces gastroesophageal reflux and aspiration in lung transplant recipients. Dig Dis Sci. 2009 May;54(5):972-9.
 Yancy WS Jr, Provenzale D, Westman EC. Improvement of gastroesophageal reflux disease after initiation of a low-carbohydrate diet: five brief cased reports. Altern Ther health med. 2001. Nov-Dec; 7(6):120,116-119.
 Austin GL, Thiny MT, Westman EC, Yancy WS Jr, Shaheen NJ. A very low-carbohydrate diet improves gastroesophageal reflux and its symptoms. Dig Dis Sci. 2006 Aug;51(8):1307-12.
 Nastaskin I, Mehdikhani E, Conklin J, Park S, Pimentel M. Studying the overlap between IBS and GERD: a systematic review of the literature. Dig Dis Sci. 2006. Dec;51(12):2113-20.
 Ledson MJ, Tran J, Walshaw MJ. Prevalence and mechanisms of gastro-oesophageal reflux in adult cystic fibrosis patients. J R Soc Med. 1998 Jan;91(1):7-9.
 Vic P, Tassin E, Turck D, Gottrand F, Launay V, Farriaux JP. Frequency of gastroesophageal reflux in infants and in young children with cystic fibrosis. Arch Pediatr. 1995 Aug;2(8):742-6.
 Fridge JL, Conrad C, Gerson L, Castillo RO, Cox K. Risk factors for small bowel bacterial overgrowth in cystic fibrosis. J Pediatr Gastroenterol Nutr. 2007 Feb;44(2):212-8.
 Piche T, des Varannes SB, Sacher-Huvelin S, Holst JJ, Cuber JC, Galmiche JP. Colonic fermentation influences lower esophageal sphincter function in gastroesophageal reflux disease. Gastroenterology. 2003 Apr;124(4):894-902.
 Lombardo L, Foti M, Ruggia O, Chiecchio A. Increased incidence of small intestinal bacterial overgrowth during proton pump inhibitor therapy. Clin Gastroenterol Hepatol. 2010 Jun;8(6):504-8.
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