Probiotic foods impact gut microbes to reduce number of unhealthy bacteria

(NaturalNews) Eating fermented foods high in probiotics may change the composition of gut bacteria in ways that may prevent or alleviate digestive conditions such as irritable bowel syndrome (IBS), according to a study conducted by researchers from the French National Institute for Agricultural Research (INRA) and Danone Nutricia Research, and published in the journal Scientific Reports on September 11.

Probiotics is a term used to refer to live microorganisms that play a beneficial role inside another organism; in the nutritional or medical context, that "other organism" refers to human beings. Studies have shown that probiotics help the body digest fiber, prevent and treat diarrhea, and help regulate the immune system, among other important effects.

Traditionally, fermented foods have nearly always been "live" foods containing probiotics. Today, consumers need to carefully read labels to make sure that such foods have not been pasteurized or otherwise "killed." To make it easier to identify live foods, many manufacturers -- particularly of yogurt -- have taken to labeling their products as containing probiotics or "live cultures."

But while humans have been consuming fermented foods for at least 12,000 years, researchers still have very little understanding of the mechanisms by which probiotics interact with our bodily systems.

Good bacteria increase; bad bacteria decrease

Previous research coordinated by INRA has pioneered new techniques for studying the billions of microorganisms that live in the gut of the average human being and has allowed the identification of many new bacterial species.

"Up until now, it was impossible to study the impact of probiotics on gut microbiota at a bacterial species level; from now on we will have a much more detailed view of the dynamics of this ecosystem," lead researcher Dusko Ehrlich said.

The new study made use of these techniques in a small pilot trial of 28 IBS patients.

"In this study, we studied the effect of the product on individuals afflicted with Irritable Bowel Syndrome (IBS), a pathology affecting 20% of the population in industrialized countries," Ehrlich said.

The makeup of participants' gut flora was analyzed both before and after they consumed
a fermented milk products containing probiotics, including Bifidobacterium lactis. The researchers found that probiotic consumption led to increases in species of bacteria that produce the chemical butyrate, which has been shown to improve gut health. Notably, studies have shown that IBS patients typically have lower levels of butyrate-producing bacteria in their guts than the general population.

The researchers also found that probiotic consumption led to a decrease in levels of the bacteria Bilophila wadsworthia, which has been linked to the development of intestinal disease.

Many mechanisms of action

Research continues to uncover the myriad of ways in which probiotics contribute to intestinal health. For example, many studies have shown that a healthy makeup of intestinal flora helps regulate the immune system, perhaps thereby helping prevent autoimmune diseases such as IBS.

A 2013 study conducted by researchers from Emory University and published in The EMBO Journal also found that, in species as distantly related as mice and fruit flies, probiotics in the genus Lactobacillus stimulated healing and regeneration in the intestinal lining.

"It is well-known that mammals live in a homeostatic symbiosis with their gut microbiota and that they influence a wide range of physiological processes," lead researcher Andrew S. Neish said. "However, the molecular mechanisms of the symbiotic cross-talk in the gut are largely unrecognized. In our study, we have discovered that Lactobacilli can stimulate reactive oxygen species that have regulatory effects on intestinal stem cells, including the activation of proliferation of these cells."

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