Prebiotics, Probiotics, and Synbiotics in IBS and Chronic Idiopathic Constipation

by David Rakel MD, FAAFP (Expert Comment)

Probiotics and Soluble Fiber Work for IBS These systematic reviews and meta-analyses published in the latest issue of the American Journal of Gastroenterology look at two therapies for irritable bowel syndrome. Ford et al reviewed the effect of probiotics and Moayyedi et al reviewed the effects of fiber. Both were found to be beneficial and may share a synergistic effect. Let’s review some terms.

Probiotics are live microorganisms that have a positive effect on health.

Prebiotics are undigested foods that probiotics needs to live and reproduce. Fiber is a prebiotic.

Synbiotics are combinations of a probiotic and a prebiotic. Synbiotics are often found in a nutritional        supplement and can contain a variety of probiotic species with a prebiotic such as inulin.

Dysbiosis is an imbalance of healthy and unhealthy bacteria (eg, Clostridium difficile colitis following antibiotic therapy).

To simplify, think of it this way:

Probiotic (microorganism) + prebiotic (fiber) = synbiotic = a synergistic therapeutic effect

The review by Ford and colleagues showed ~21% therapeutic response over placebo with probiotics for IBS.  It appears that Lactobacillus, Bifidobacterium, Saccharomyces (a yeast), Streptococcus, and Escherichia coli all showed benefit.

The review by Moayyedi and colleagues showed that soluble fiber improved IBS symptoms by about 17% over placebo. Psyllium was found to have the greatest benefit.

When fiber and bacteria are combined, fermentation ensues, which produces short-chain fatty acids (SCFA) such as butyrate, acetate, and propionate. These SCFA are the main source of energy for the enterocytes and help keep inflammation in check while repairing the gut lining. Using both a probiotic and prebiotic may have a synergistic effect not only for IBS but also for the overall health of the GI ecosystem.

Therapeutic summary for IBS:

1. Consider a probiotic that contains Lactobacillus and Bifidobacterium species at a dose of at least 108 colony-forming units (CFU) daily for 1 month. Then encourage fermented foods as a continued source of probiotics, such as yogurt, miso, and sauerkraut.

2. Consider psyllium (1 tbsp in 8–10 oz of water) one to two times daily for 1 month, then encourage a soluble-fiber rich diet through the regular consumption of vegetables, high-fiber grains, and fruit.

3. Be sure to address the mind–body connection by encouraging stress reduction.

Reviewed/posted by Dr. Russell

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