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'Good' Bacteria Might Prevent Intestinal Problems From Chronic Stress

By Miranda Hitti, Reviewed by Ann Edmundson, PhD, MD

WebMD Medical News, April 25, 2006 -- Gut-friendly bacteria called probiotics may help prevent intestinal problems linked to chronic stress, a new study shows.

The study appears in Gut's "online first" edition. The researchers included Philip Sherman, MD, FRCP(C). Sherman works in the gastroenterology and nutrition division of Toronto's Hospital for Sick Children.
Sherman's team tested probiotics on rats, not people. Those tests showed that probiotics seemed to thwart some intestinal problems linked to chronic psychological stress.
"Stress is a common experience of daily living," the researchers write. The influence of stress on chronic intestinal disorders is "well documented," they write, spotlighting irritable bowel syndrome and inflammatory bowel diseases such as Crohn’s Disease and ulcerative colitis.

Water Laced With Probiotics

First, the researchers assigned male rats into two groups, lacing the drinking water of one group of rats with powder containing probiotics.
There are many types of probiotics. The probiotics powder used in Sherman's study contained a strain of Lactobacillus rhamnosus and a strain of Lactobacillus helveticus.
For comparison, the other group of rats got sterile drinking water with no probiotics.
Seven days later, the researchers put half of the rats in each group under psychological stress. The point was to see if the rats that had been drinking water containing probiotics had a different intestinal response to chronic stress than rats that had been drinking sterile water without probiotics.

Stress Test

To create psychological (but not physical) stress in the rats, the researchers put each rat on a platform in the middle of a plastic container filled with warm water.
The platform stood 1 centimeter above the water. Rats don't like to swim, so being on a little platform surrounded by water isn't their cup of tea.
The rest of the rats were placed on the same type of platform in an identical container but without the water. That setting was designed to be much less stressful for the rats.
The rats spent one hour a day for 10 days on their platforms. After that, the researchers checked the rats' intestines.

Study's Results

All of the rats remained healthy during the study. "There were no signs of diarrhea, weight loss, or loss of appetite," the researchers write.
However, closer examination showed some subtle differences among the groups of stressed rats.
Harmful bacteria latched onto cells in the intestinal wall and nearby lymph nodes of stressed rats with sterile drinking water. But that wasn't true of stressed rats that had been drinking probiotics-laced water.
Stressed rats that had gotten probiotics in their drinking water showed no signs of harmful bacteria leaking to their lymph nodes. Probiotics -- not harmful bacteria -- had attached to their intestinal walls.

2 Key Effects

Probiotics appeared to have two main actions in the rats, the researchers note:

  • Probiotics may have successfully competed against harmful bacteria for a spot on the rats' intestinal walls.
  • Probiotics may also have helped maintain intestinal barriers, preventing leakage of harmful bacteria.

The process behind those actions isn't clear, but probiotics may stick better to intestinal walls than harmful bacteria, note Sherman and colleagues.

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