If you thought dietary fibre was just for digestive health, then think again.
Researchers say that a common foodstuff can help us to sleep better and stress less. And with the coronavirus upsetting millions on both fronts, this news is good news.
Lack of sleep is a costly health and economic problem across the globe.
In late 2018, the federal government acknowledged the negative economic and social impact of poor sleep, when it announced a parliamentary inquiry into whether Australians are getting enough sleep.
A report released late last year by the Royal Australian College of GPs (RACGP) uncovered just how widespread sleep problems are in Australia.
“About 60 per cent of people report at least one sleep symptom occurring three or more times per week,” said Professor Robert Adams, lead author of the report and spokesperson for the Sleep Health Foundation.
He said common symptoms included trouble falling asleep, staying asleep, or waking too early and not being able to get back to sleep.
Now, University of Colorado Boulder research shows that specific fibres, known as prebiotics, can improve sleep and boost stress resilience by influencing gut bacteria.
The research could lead to new approaches to treating sleep problems.
Robert Thompson, a postdoctoral researcher in the Department of Integrative Physiology and lead author of the study, says: “The biggest takeaway here is that this type of fibre is not just there to bulk up the stool and pass through the digestive system. 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 behaviour.”
Most people are familiar with probiotics, friendly bacteria present in fermented foods such as yoghurt and sauerkraut and regularly suggested for anyone taking antibiotics. More recently, scientists have taken an interest in prebiotics – dietary compounds that humans cannot digest but which serve as nourishment for our microbiome, or the trillions of bacteria living within us. While not all fibres are prebiotics, many fibrous foods, such as leeks, artichokes, onions and certain whole grains, are rich in them.
In an earlier study, the researchers started adolescent male rats on either standard chow or chow infused with prebiotics and tracked them before and after stress tests.
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.
The new study sheds light on how prebiotics can help bust stress.
“We know that this combination of dietary fibres helps promote stress robustness and good sleep and protects the gut microbiome from disruption,” said senior author and Integrative Physiology Professor Monika Fleshner. “With this new study, we wanted to try to identify the signal.”
Using a technology called mass spectrometry to analyse the rats’ faecal 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 signalling pathways, influence behaviour. The rats’ metabolome also looked different after stress.
“Our results reveal novel signals that come from gut microbes that may modulate stress physiology and sleep,” said Prof. Fleshner.
While prebiotic dietary fibre is certainly healthy, it’s uncertain whether just loading up on foods rich in it 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.
“You’d probably have to eat a whole lot of lentils and cabbage to see any effect,” said Mr Thompson.
Prebiotic supplements abound on natural food store shelves. But Prof. Fleshner said it was too soon to say whether a supplement or drug containing such compounds would be safe and effective for everyone. Depending on what their microbial make-up is, different people might respond differently.
“These are powerful molecules with real neuroactive effects and people need to exercise some caution,” she said.
Human studies are already in the works at CU Boulder.
Ultimately, Prof. Fleshner believes their research could lead to a new class of options for people who can’t sleep but don’t like taking narcotics.
“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,” she said. “It's exciting to think about.”
Do you suffer from sleep problems? Do you wake in the night and struggle to get back to sleep? Have you heard about prebiotics?
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Disclaimer: This article contains general information about health issues and is not advice. For health advice, consult your medical practitioner.
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