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From the Townsend Letter
February / March 2013

Small Intestine Bacterial Overgrowth:
Often-Ignored Cause of Irritable Bowel Syndrome

by Allison Siebecker, ND, MSOM, LAc, and
Steven Sandberg-Lewis, ND, DHANP

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If the measured gases do not rise until after 120 minutes, it is possible that this is due to a prolonged transit time, which we have seen in patients with severe constipation. In such a patient with the expected symptom picture for constipation type SIBO, a significant rise at 140 minutes may be interpreted as a positive test.

Breath testing may be used in pediatric cases, so long as the child can follow instructions to blow. For those under 3 years old, testing is best done on site at a lab due to differences in collection methods versus at-home kits. Pediatric lactulose dosing is 1g/kg body weight with a maximum of 10 g (22 pounds and above receive the max/adult dose of 10 g).41 Lactulose requires a prescription.

Treatment of SIBO
In 2006, Pimentel shared his treatment algorithm for IBS with SIBO which included the use of either antibiotics, elemental diet or both.28 Our approach offers two additional options: diet and herbal antibiotics (Figure 3).

Figure 3

SIBO Treatment Protocol

We advise diet (Specific Carbohydrate Diet or Gut and Psychology Syndrome Diet) for all SIBO patients.42,43 Since bacteria use carbohydrates as their energy source and ferment them to gas, a low-carbohydrate diet can directly reduce symptoms by decreasing the amount of gas produced.44 Reducing carbohydrates may also reduce the overall bacterial load as the food supply shrinks, though formal studies to validate this are lacking. These diets decrease polysaccharides, oligosaccharides, and disaccharides by eliminating all grains, starchy vegetables, lactose, sweeteners other than honey, and in the beginning, beans. Many patients experience a rapid and significant decrease in symptoms after starting a SIBO diet. The Specific Carbohydrate Diet (SCD) has been reported to have an 84% success rate for inflammatory bowel disease, a condition commonly associated with SIBO.45,46

Diet alone has proven successful for infants and children, but for adults one or more of the other three treatment options are often needed to reduce bacteria quickly, particularly in cases in which diet needs to be very restricted to obtain symptomatic relief. Additionally, any diet will always need to be customized to the individual by trial and error over time. That being said, following a diet prescription offers a place to start. We have found that using the SCD or Gut and Psychology Syndrome Diet (GAPS) as the core diet (Table 1), with the incorporation of the fruit and vegetable recommendations from the Low FODMAP Diet (Table 2), is an effective approach. The Low FODMAP Diet is an IBS treatment diet that has investigated the fermentable levels of carbohydrate foods (fruits, vegetables, and grains) and has a success rate of 76%.47 The FODMAP Diet is not specifically designed for SIBO and therefore does not eliminate polysaccharide and disaccharide sources such as grains, starch, starchy vegetables, and sucrose. Eliminating these poly- and disaccharides is essential in SIBO because SIBO creates a situation in which these normally well-absorbed carbohydrates, foods that usually go to feed the host, can now feed bacteria inappropriately located in the small intestine, creating symptoms and worsening the problem (Figure 1).

Table 1

SCD/GAPS Resources

Table 2

SIBO Fruits & Vegies

Low-carbohydrate diets are weight-loss diets. Particular attention must be paid to those who are low weight or underweight. If a low-carb SIBO diet is causing too much weight loss, this dietary strategy will need to be altered to allow for more carbohydrates. In these circumstances, one or more of the other three treatment options should be considered along with white rice, glucose, and other carbohydrate sources.

Diet is also essential for prevention, post SIBO treatment.

Elemental Diet
An elemental diet can be used in place of antibiotics or herbal antibiotics to rapidly decrease bacteria. Elemental diets are powdered predigested nutrients that are mixed with water and used in hospitals for various gastrointestinal disorders to give digestion a rest. The concept behind this treatment for SIBO is that the nutrients will be absorbed before having a chance to feed the bacteria, thus feeding the person but starving the bacteria. It is used in place of all meals, for 2 to 3 weeks, and has a success rate of 80% to 85%.48 Elemental diets are not protein powders or cleansing/detox formulas. They are available over the counter and are not covered by insurance, which can make this treatment course costly.

The most studied and successful antibiotic for SIBO is rifaximin. It has a broad spectrum of activity and is nonabsorbable. Its nonabsorbability allows it to stay in the intestine, acting locally and it is therefore less likely to cause systemic side effects common to standard absorbable antibiotics.49 Rifaximin has up to a 91% success rate and is given at 550 mg t.i.d × 14 days.50,51 Additionally, rifaximin has several unique benefits: it does not cause yeast overgrowth, it decreases antibiotic resistance in bacteria by reducing plasmids, antibiotic resistance does not develop to it, making it effective for retreatments, and it is anti-inflammatory, decreasing intestinal inflammatory cytokines and inhibiting NF-kb via the PXR gene.52–54 Rifaximin is best used for SIBO when hydrogen is present, but when methane gas is present, double therapy of rifaximin plus neomycin (500 mg b.i.d. × 14 days) is more effective.55 Many gastroenterologists use metronidazole (250 mg t.i.d. × 14 days) as an alternative to neomycin (unpublished). Since different antibiotic regimens are recommended based on the gas type, breath testing is necessitated when considering this treatment.

Herbal Antibiotics
While there has only been one published report of herbal antibiotics in the treatment of SIBO, our experience is that they have similar effectiveness to antibiotics.56 We have used the following botanicals: Allium sativum, Hydrastis canadensis, and other berberine-containing herbs, Origanum vulgare, cinnamon, and Azadirachta indica. We have used these as both single agents and in various combinations at dosages that are at the upper end of label suggestions × 30 days. Specific single dosages we have used include allicin extract of garlic: 450 mg b.i.d.–t.i.d., goldenseal/berberine: 5g q.d. in split dosage, emulsified oregano: 100 mg b.i.d., and neem: 300 mg t.i.d. Our breath testing has validated the need for the longer treatment period of 30 days for herbal antibiotics compared with 14 days for antibiotics. We have also observed with this method prolonged die-off reactions, which can last for the duration of treatment course. Studies on herbal antibiotics for SIBO are needed, particularly to identify botanicals effective in reducing methane.

Prevention of SIBO
SIBO is a disease that relapses because eradication itself does not always correct the underlying cause.57,58 Pimentel's 2006 treatment algorithm includes 2 essential preventions: diet and a prokinetic (motility agent). Our approach offers 3 optional additions: hydrochloric acid, probiotics, and brush border healing supplements (Figure 3).

A key underlying cause of SIBO is thought to be deficiency of the migrating motor complex (MMC), which moves bacteria down into the large intestine during fasting at night and between meals.59 Prokinetics stimulate the MMC, symptomatically correcting this underlying cause. Prokinetics studied for SIBO include low-dose naltrexone 2.5 mg q.d., h.s., or b.i.d., low-dose erythromycin 50 mg h.s., and tegaserod 2–6 mg h.s.59,60 Tegaserod has a higher success rate for SIBO prevention versus erythromycin, but has been withdrawn from the US for safety reasons.59 Prucalopride 1–4 mg h.s. is not yet available in the US but is a safer alternative to tegaserod.61 A trial removal of the prokinetic at ≥ 3 months is suggested but continued long-term use may be needed.28

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