The indigestible compounds found in high-fiber foods and dairy do more than help people poop. They could also dramatically improve your quality of life, too.
According to new research in rats, eating a diet high in these "prebiotics" supports a powerful "symbiotic relationship" in the body, promoting better sleep and less stress.
The results, while preliminary, suggest a diet high in prebiotics may combat stress and poor sleep in humans, both of which can cascade into myriad other health issues, from memory problems to premature aging.
“Armed with this information, we might be able to develop a targeted therapeutic that boosts the molecules that buffer against stress and tamps down the ones that seem to disrupt sleep,” Monika Fleshner, a co-author on the new study and researcher at the University of Colorado, said in a statement.
“It’s exciting to think about," she says.
The findings were published this week in the journal Scientific Reports.
Prebiotics may not be as famous as gut bacteria-boosting probiotics, but they are near ubiquitous in our diets, and can be found in foods as diverse as oats and garlic. But unlike probiotics, humans cannot actually digest prebiotics. Still, they serve a vital function: Prebiotics feed the trillions of microorganisms that live in our guts, promoting a happy ecosystem of bacteria.
This ecosystem, the gut microbiome, may in turn influence our own brain function and behavior.
Prebiotics' positive effects seem to be driven by communication between the molecules produced during cell metabolism, known as metabolites, and the brain. Prebiotics boost production of metabolites that appear to act as a buffer against stress and bad sleep. At the same time, prebiotics led to fewer metabolites linked to these problems, the study suggests.
To understand the mechanisms underlying this powerful “buffering effect,” researchers put 26 rats on a diet high in four prebiotics: galactooligosaccharides, polydextrose, lactoferrin, and milk fat globular protein. Over five weeks, the researchers compared these rats' sleep quality and stress response to 26 rats fed a standard chow diet. Before and after the experiment, researchers took fecal samples from the rats, analyzing the metabolites in their stool.
The prebiotic-diet rats had dozens of additional metabolites in their stool samples than the standard chow group, including fatty acids, sugars, and steroids. The rats which ate standard chow diet also showed spikes in sleep-disrupting metabolites, while the prebiotic group did not.
The findings suggest the additional, "good" metabolites found in the prebiotic group are communicating with the rats' brains, boosting their resilience to stress, and promoting good sleep, the researchers say.
Inside the metabolome
The results gel with older research in mice, which suggests a prebiotic diet boosts time spent in restorative non-rapid-eye-movement (NREM) sleep, a stage of sleep when the body repairs and regrows tissue.
The 2017 study also found that, after experiencing stress, mice fed a prebiotic-heavy diet also spend more time in rapid-eye-movement (REM) sleep, a stage critical for stress recovery.
Conversely, mice eating standard chow suffer a drop in the diversity of gut flora after stress. Prebiotic-eating mice, however, seem to be protected from this negative shift.
Together, these rodent studies offer hope for future treatments for humans who experience chronic stress or difficulty sleeping, and suggest that doing something so simple as eating a high-fiber diet could boost resiliency in the face of adversity.
“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," Robert Thompson, co-author of the new study and a researcher at the University of Colorado, said 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."
The findings offer a foundation for future studies in humans, the researchers say. They are working to replicate their results in humans.
Until they complete that study, how prebiotics may influence sleep and stress in humans isn't clear. So we cannot say for sure whether upping our intake of prebiotic-rich foods like artichokes or cabbage, or taking prebiotic supplements, leads to better sleep and less stress.
Dietary prebiotics produce favorable changes in the commensal gut microbiome and reduce host vulnerability to stress-induced disruptions in complex behaviors such as sleep. the mechanisms for how prebiotics modulate stress physiology remain unclear; however, emerging evidence suggests that gut microbes and their metabolites may play a role. this study tested if stress and/or dietary prebiotics (test diet) alter the fecal metabolome; and explored if these changes were related to sleep and/or gut microbial alpha diversity. Male F344 rats on either Test or Control diet were instrumented for electroencephalography biotelemetry measures of sleep/wake. After 5 weeks on diet, rats were either stressed or remained in home cages. Based on untargeted mass spectrometry and 16S rRNA gene sequencing, both stress and Test diet altered the fecal metabolome/microbiome. In addition, Test diet prevented the stress-induced reduction in microbial alpha diversity based on PD_Whole_Tree, which has been previously published. network propagation analysis revealed that stress increased members of the neuroactive steroidal pregnane molecular family; and that Test diet reduced this effect. We also discovered links between sleep, alpha diversity, and pyrimidine, secondary bile acid, and neuroactive glucocorticoid/pregnanolone-type steroidal metabolites. these results reveal novel microbial- dependent metabolites that may modulate stress physiology and sleep.