Wednesday, January 20, 2010

Gases, Prebiotics, Probiotics and Irritable Bowel Syndrome

Ilya Ilyich Mechnikov, by Nadar.
Image via Wikipedia
This is an un-sanitary topic. Yet, for those who have an illness such as irritable bowel syndrome (IBS) is a life quality issue. For the same level of colonic distension, pain and discomfort is worse for people suffering from IBS.

Lately, I started reading about prebiotics and probiotics. This led me to read on our gut microbiota. Some consider our gut micorbiota an organ. Yes, an organ that we did not learn about while in medical school(Gibson 2004).
Above picture is of the 1908 Noble prize in medicine winner Ilya Ilych Mechnikov who poineered interest in gut microbiotia and its connection to health.
Gut microbiota is the bacteria and other micro-organisms living in our gut. Number of their cells is 10 times our cells. They are not all parasitic or pathogenic, rather most are symbiotic. They offer many health benefits. They even feed us. They produce short chain fatty acids that our enterocytes feed on. (Bixquert Jiménez 2009) This is an area of active research and most of the benefits are shown on animal models. For a handful of reasons (big corporations being one) I don’t see this science advancing fast enough. Having said this, there are studies on humans showing some benefits in certain disease entities.
Let’s go back to gases:

I think we all agree that gases are mainly produced by these bacteria fermenting the food we eat. And, you probably noticed that some foods produce gasses more than others. But, this is not all of it. Lumping all our gut’s bacteria together (as with IBS bacterial overgrowth theory) is as lumping all mammals together. You agree with me that elephants and tigers are quite different. There are 400-500 known species in our gut. (Jimenez 2009) These have an undefined number of strains or subspecies.
Lactobacillus and bifidobacterium are two genera that tend not to produce gas when fermenting carbohydrates. (Spiller 2008) And, the more we have of these the less we should have of the gas producing ones, such as clostridia. Therefore, if we can increase non-gas producing bacteria we could reduce gas. There are different methods we can alter our gut bacteria, two have been shown to increase bifidobacterium: prebiotics, and probiotics.
The easiest to explain is probiotics: just ingest live bifidobactirum;  some of its strains can bypass the harsh environment produced by gastric acid and bile salts. Live bifidobactirum are found in probiotics capsules and are added to dairy products such as Danon’s Activia yogurt. A study sponsored by Danon, showed if those with constipation predominant IBS eat two servings of Activia yogurt, they would have less gas. (Guyonnet et al. 2007) Something worth noting, we should narrow down to the strain specific level when describing probiotics. For example the tested Danon strain was:
Genus:    Bifidobacterium
Species: animalis
Strain:    DN-173 010
The other method to increase good bacteria is to feed them. Some types of complex carbohydrates that are not digested by humans reach our colon and are fermented by bacteria. It is found that eating certain types of complex carbohydrates preferentially promotes the growth of Bifidobacteria.  Inulin and transgalacto-oligosaccharides are two prebiotics. (Gibson 2004) Lactulse, although not food exerts a prebiotic effect.  There are no properly conducted studies that show any clinical benefits of prebiotics for treating bloating in IBS. The opposite is true, there are studies that showed a worsening in bloating with lactulose. (Spiller 2008) Therefore, prebiotics and foods that alter gut microbiota in a positive way need further investigation which will probably be hampered by reduced funding. Big corporations (surprisingly!) can patent probiotics strains clinical use which probably encourages funding into probiotics and not prebiotics research.

Bixquert Jiménez, M., 2009. Treatment of irritable bowel syndrome with probiotics. An etiopathogenic approach at last? Revista Española De Enfermedades Digestivas: Organo Oficial De La Sociedad Española De Patología Digestiva, 101(8), 553-564.

Gibson, G.R. et al., 2004. Dietary modulation of the human colonic microbiota: updating the concept of prebiotics. Nutrition Research Reviews, 17(2), 259-275.

Guyonnet, D. et al., 2007. Effect of a fermented milk containing Bifidobacterium animalis DN-173 010 on the health-related quality of life and symptoms in irritable bowel syndrome in adults in primary care: a multicentre, randomized, double-blind, controlled trial. Alimentary Pharmacology & Therapeutics, 26(3), 475-486.

Spiller, R., 2008. Review article: probiotics and prebiotics in irritable bowel syndrome. Alimentary Pharmacology & Therapeutics, 28(4), 385-396.

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