Prebiotics, plant fibers that promote the growth of helpful bacteria in the gut, can help protect "good" intestinal bacteria and restore healthy sleep patterns after a stressful event, says a study published in the journal Frontiers in Behavioral Neuroscience.

While probiotics, which are "good" bacteria found in yogurt and other fermented foods, are known for easing digestive problems and keeping the gut healthy, prebiotics are less well understood.

Prebiotics are certain types of non-digestible fibers that probiotic bacteria feed on, such as the fibers found in many plant sources like asparagus, oatmeal, and legumes.

Researchers at the University of Colorado, Boulder, knew that stress could upset the gut's microbiome, and wondered if prebiotics might help restore it.

"Acute stress can disrupt the gut microbiome," said Dr. Agnieszka Mika, "and we wanted to test if a diet rich in prebiotics would increase beneficial bacteria as well as protect gut microbes from stress-induced disruptions.

"We also wanted to look at the effects of prebiotics on the recovery of normal sleep patterns, since they tend to be disrupted after stressful events," Mika said.

In the study, rats received prebiotic diets for several weeks prior to experiencing stress and were compared with control rats that did not receive the prebiotic-enriched diet. The rats that ate prebiotics prior to the stressful event — which was the human equivalent of a car accident or the death of a loved one — did not experience stress-induced disruption in their gut microbiota, and also recovered healthier sleep patterns sooner than controls.

Should you include prebiotics in your diet to help cope with stress? "So far no adverse effects from prebiotics have been reported," said Dr. Mika, "and they are found widely in many plants, and are already commercially available."

Top food sources of prebiotics include raw dandelion greens, garlic, and leeks, and raw or cooked onions.