Prebiotics found to influence gut metabolites, buffering stress, improving sleep

Prebiotics may improve sleep and boost stress resilience by influencing gut bacteria and the metabolites they produce, according to new research by the University of Colorado Boulder and published in the journal Scientific Reports.

Most practitioners are familiar with probiotics, good bacteria present in fermented foods like yogurt and sauerkraut. More recently, the medical community has taken an interest in prebiotics, dietary compounds that humans cannot digest but serve as nourishment for the gut microbiome. While not all fibers are prebiotics, many fibrous foods such as leeks, artichokes, onions, and certain whole grains are rich in them.

For the study, the researchers started adolescent male rats on either standard chow or chow infused with prebiotics and tracked an array of physiological measures before and after the rats were stressed. Those on the prebiotic diet spent more time in restorative non-rapid-eye-movement (NREM) sleep. After stress, they also spent more time in rapid-eye-movement (REM) sleep, which is believed to be critical for recovery from stress.

While rats eating standard chow saw an unhealthy flattening of the body's natural temperature fluctuations and a drop in healthy diversity of their gut microbiome after stress, those fed prebiotics were buffered from these effects, according to the study.

Using a technology called mass spectrometry to analyze the rats' fecal samples, the researchers measured metabolites, or bioactive small molecules produced by bacteria as food is broken down. They found rats on the prebiotic diet had a substantially different metabolome, or make-up of metabolites. Theirs was higher in dozens of them, including fatty acids, sugars, and steroids, which may, via gut-brain signaling pathways, influence behavior. The rats' metabolome also looked different after stress, the researchers said.

While prebiotic dietary fiber is certainly healthy, it's uncertain whether loading up on foods rich in prebiotics can promote sleep. The rats were fed very high doses of four specific prebiotics, including galactooligosaccharides, which are present in lentils and cabbage; polydextrose (PDX) an FDA-approved food additive often used as a sweetener; lactoferrin, found in breast milk; and milk fat globular protein, abundant in dairy products. In small amounts, the results were insignificant, the researchers said.

Supplement companies are already producing prebiotic supplements for consumer use, but researchers said it is too soon to say whether a supplement containing such compounds would be significant and effective for everyone. The researchers caution that patients may respond differently depending on their unique genetic and microbial make-up.

However, the research could ultimately lead to new approaches to treating sleep problems, which affect 70 million Americans, according to Robert Thompson, PhD, a postdoctoral researcher in the Department of Integrative Physiology and lead author of the study.

"The biggest takeaway here is that this type of fiber is not just there to bulk up the stool and pass through the digestive system," said Thompson in a statement. "It is feeding the bugs that live in our gut and creating a symbiotic relationship with us that has powerful effects on our brain and behavior."