The benefits associated with pro- and prebiotics are strain- and substance-specific, respectively, and must be shown through adequate clinical trials reflective of the dose of pro- or prebiotics present in the food at the time of consumption.
Probiotics and prebiotics are components present in foods, or that can be incorporated into foods, which yield health benefits related to their interactions with the gastrointestinal tract (GI). While the benefits of prebiotics have come to light in more recent years, recognition of probiotic effects dates back to the 19th century when the French scientist Louis Pasteur (1822 -1895) postulated the importance of microorganisms in human life; this was further reinforced by work done by 1908 Nobel Prize-winner Elie Metchnikoff.
"We found that dietary prebiotics can improve non-REM sleep, as well as REM sleep after a stressful event," said Robert Thompson, a post-doctoral researcher in the Department of Integrative Physiology and first author of the new study, published in the journal Frontiers in Behavioral Neuroscience.
Prebiotics are dietary fibers found naturally in foods like chicory, artichokes, raw garlic, leeks and onions. When beneficial bacteria digest prebiotic fiber, they not only multiply, improving overall gut health, but they also release metabolic byproducts. Some research suggests these byproducts can influence brain function, explains lead author Monika Fleshner, a professor in the Department of Integrative Physiology.
Probiotics and Prebiotics Influence Neuropsychological Conditions - 6 Surprising Facts About Microbes In Your Gut
For the study, the researchers fed 3-week-old male rats a diet of either standard chow or chow that included prebiotics. They then monitored the rats' body temperature, gut bacteria and sleep-wake cycles -- using EEG, or brain activity testing -- over time.
They found that the rats on the prebiotic diet spent more time in non-rapid-eye-movement (NREM) sleep, which is restful and restorative, than those on the non-prebiotic diet.
"Given that sufficient NREM sleep and proper nutrition can impact brain development and function and that sleep problems are common in early life, it is possible that a diet rich in prebiotics started in early life could help improve sleep, support the gut microbiota and promote optimal brain/psychological health," the authors wrote.
After being exposed to a stressor, the rats on the prebiotic diet also spent more time in rapid-eye-movement (REM) sleep. REM sleep is believed to be critical for promoting recovery from stress, with research showing that those who get more REM sleep post-trauma are less likely to suffer from post-traumatic stress disorder.
Stress has previously been shown to reduce healthy diversity of gut bacteria and to lead to a temporary flattening of natural fluctuations in body temperature.
But rats on the prebiotic diet were buffered from these impacts, maintaining a healthy and diverse gut microbiota and normal temperature fluctuations even after stress exposure.
Fleshner said it's far too early to recommend prebiotic supplements as a sleep aid. More studies are in the works to examine what role prebiotics can play in promoting sleep, or buffering stress in people.
But she does recommend loading up on healthy prebiotic fiber from food. "It can't hurt and it might help," she said.
The healthful effects of pre- and probiotics factor in their potential impact on the balance of the body’s microflora, and directly or indirectly in their enhancement of the function of the gut and systemic immune system. Although benefits vary, depending on the type and amount of a pre- or probiotic consumed, experts agree that daily consumption of foods containing these functional components is beneficial. In addition, effects of probiotics are strain-specific and must be demonstrated through appropriate clinical trials.