Sunday, August 5, 2012

Carbohydrates for your bacteria

Our bacteria are picky eaters. Some of them - like Prevotelia - prefer a high carbohydrate diet, while others - like Bacteroides - stick to unhealthy western lifestyle with lots of meat and fat. The most prevalent bacteria in the gut of horses, cows and goats prefer people consuming alcohol and polyunsaturated fats. Methanobrevibacter is most abundant in anorexic nervosa patients. Gram negative bacillus Bilophila wadsworthia loves people with gangrenous appendicitis or those whose diets are high in milk fat. The most widely promoted prebiotics inulin and fructooligosaccharides seem to attract Bifidobacteria. What about diets low in poorly absorbed fermentable carbohydrates aka FODMAPs that seem to aggravate irritable bowel syndrome (IBS) ? Which bacteria is responsible?

A recently completed clinical trial  looked at the effects of low-FODMAP dieting by analyzing Short Chain Fatty Acids (SCFA), pH and other qualities of stool.

The data show that with less FODMAPs in the diet, there seemed to be less water and fermentable substances in the proximal colon, and less gastrointestinal distress in patients with IBS. This randomized controlled trial also demonstrated a reduction in concentration and proportion of luminal bifidobacteria after 4 weeks of fermentable carbohydrate restriction.

Bifidobacteria? Isn't it one of the "friendliest" bacteria alleviating symptoms in IBS, by normalizing the ratio of an anti-inflammatory to proinflammatory cytokines? At least, as was shown for B.infanitis 35624 and B. animalis DN-173 010 in different studies. It looks like that the most effective species and the implications of diets on the gastrointestinal microbiota are still uncertain. After all, another study showed that even though IBS sufferers have lower amounts of Bifidobacteria than non-sufferers, those whose symptoms are less severe show even lower amounts of Bifidobacteria in their samples.

What can we say except that more studies are needed...


Staudacher HM, Lomer MC, Anderson JL, Barrett JS, Muir JG, Irving PM, & Whelan K (2012). Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. The Journal of nutrition, 142 (8), 1510-8 PMID: 22739368

Suzanne Devkota, Yunwei Wang, Mark W. Musch, Vanessa Leone, Hannah Fehlner-Peach, Anuradha Nadimpalli, Dionysios A. Antonopoulos, Bana Jabri, Eugene B. Chang. Dietary-fat-induced taurocholic acid promotes pathobiont expansion and colitis in Il10−/− mice. Nature, 2012; DOI: 10.1038/nature11225

Cui S, & Hu Y (2012). Multistrain probiotic preparation significantly reduces symptoms of irritable bowel syndrome in a double-blind placebo-controlled study. International journal of clinical and experimental medicine, 5 (3), 238-44 PMID: 22837798

Wu GD, Chen J, Hoffmann C, Bittinger K, Chen YY, Keilbaugh SA, Bewtra M, Knights D, Walters WA, Knight R, Sinha R, Gilroy E, Gupta K, Baldassano R, Nessel L, Li H, Bushman FD, & Lewis JD (2011). Linking long-term dietary patterns with gut microbial enterotypes. Science (New York, N.Y.), 334 (6052), 105-8 PMID: 21885731

O'Mahony L, McCarthy J, Kelly P, Hurley G, Luo F, Chen K, O'Sullivan GC, Kiely B, Collins JK, Shanahan F, Quigley EM. Lactobacillus and bifidobacterium in irritable bowel syndrome: symptom responses and relationship to cytokine profiles. Gastroenterology. 2005 Mar;128(3):541-51.