To summarize: Probiotics can be good for you. Stress always exacerbates underlying illness and weakness.
Probiotics do not cancel out stress, but they do help to regulate the immune system and therefore may help to mitigate some of the effects of stress on your IBS. What they didn’t mention was that probiotics may help your IBS even without the involvement of stress. Or they may not help. And in some cases they can make your IBS worse. That is why you should see an expert in IBS.
Excerpt from ScienceDaily:
For those with irritable bowel syndrome who wonder if stress aggravates their intestinal disorder, a new University of Michigan Health System study shows it’s not all in their head.
Researchers revealed that while stress does not cause IBS, it does alter brain-gut interactions and induces the intestinal inflammation that often leads to severe or chronic belly pain, loss of appetite and diarrhea.
Stress has a way of suppressing an important component called an inflammasome which is needed to maintain normal gut microbiota, but probiotics reversed the effect in animal models, according to findings published online ahead of print in Gastroenterology.
“The effect of stress could be protected with probiotics which reversed the inhibition of the inflammasome,” says senior study author and gastroenterologist John Y. Kao, M.D., associate professor of internal medicine at the University of Michigan. “This study reveals an important mechanism for explaining why treating IBS patients with probiotics makes sense.”