Gut Reaction

by Women's Bran Health Initiative:The human body is host to trillions of microbes. In fact, slightly more than half of the cells found in our bodies are microbes – mostly bacteria, but also fungi, viruses, protozoa, archaea, and other microorganisms. The majority of these microbes reside in the gastrointestinal (GI) tract – commonly referred to as the “gut” – and the rest can be found in different parts of the body, including on the skin, in the urogenital tract, and in the nasal, oral, and otic (ear) cavities. The microbes in the gut are estimated to weigh between one and two kilograms, which is approximately the same weight as the human brain. Collectively, all of these microbes make up what is referred to as the human microbiome.Microbes handle a variety of essential and beneficial functions in the human body. They play a fundamental role in digestion, nerve cell growth and survival, immunity, and inflammation.EVIDENCE IS EMERGING THAT SUGGESTS MICROBES AFFECT COGNITION, BEHAVIOUR, AND MENTAL HEALTH, PARTICULARLY THROUGH INTERACTIONS BETWEEN THE GUT MICROBES AND THE CENTRAL NERVOUS SYSTEM, COMMONLY REFERRED TO AS THE “GUT-BRAIN AXIS.”“In recent years, our appreciation of how important these microbial communities are to many aspects of how the human body functions has grown dramatically,” explained Dr. Geraint Rogers, Director of Microbiome Research at South Australian Health and Medical Research Institute and Professor at Flinders University School of Medicine. “For example, we know that animals raised in a germ-free environment show substantially altered immune and metabolic function compared to animals with a normal microbiome. And, evidence has demonstrated that disruption of microbiota in humans is associated with the development of a variety of diseases.”Research has found associations between the composition of the gut microbiome and inflammatory bowel disease, autoimmune arthritis, type 2 diabetes, obesity, atherosclerosis, anxiety, and depression.THERE IS ALSO EMERGING EVIDENCE THAT LINKS DISTURBANCES TO INTESTINAL MICROBIOTA WITH NEUROLOGICAL CONDITIONS, SUCH AS MULTIPLE SCLEROSIS, AUTISM SPECTRUM DISORDER, PARKINSON’S DISEASE, AND ALZHEIMER’S DISEASE (AD).In three recent studies set out below, the researchers examined the relationship between the microbiome and the development of Alzheimer’s disease.

• A review article by Dr. Francesca Pistollato and colleagues – published in Nutrition Reviews in 2016 – reported that bacteria in the gut can produce significant amounts of amyloids and lipopolysaccharides, which may play a role in the progression of AD (accumulation of amyloid-beta plaques in the brain is one of the hallmarks of AD). The researchers also explored how certain nutrients affect the composition of gut microbiota, and thus the formation and aggregation of amyloid-beta in the brain.
• More recently, a study conducted by Nicholas M. Vogt and colleagues examined the differences between the microbiomes of individuals diagnosed with AD versus those without. The researchers analyzed fecal samples from 25 participants diagnosed with AD and 25 age- and sex-matched controls. The results indicated that the microbiomes of AD participants had decreased microbial diversity and were distinct in composition compared to the controls. “We discovered that the abundance of certain microbes was different in people with dementia due to Alzheimer’s, compared to the control group,” explained Dr. Barbara Bendlin, Associate Professor at the University of Wisconsin, and one of the authors of the study. “Fourteen of these microbe types were more abundant, while 68 types were less abundant in those with Alzheimer’s.” These findings were published in Scientific Reports in 2017.
• One of the topics covered in a review article by Dr. Helen Tremlett and colleagues, published in American Neurological Association in 2017, was the association between the oral microbiome and Alzheimer’s disease. The researchers noted that poor dental status has been linked to Alzheimer’s disease or reduced cognitive function in a number of studies. They also noted that periodontal disease has been associated with increased amyloid in the brain, even in subjects that are cognitively normal.

“Treatments” that Target the MicrobiomeGiven what is known so far about the involvement of gut microbiome in human health and disease, it is not surprising that researchers are currently examining the possibility that health could be boosted or disease prevented (or even cured) by targeting the microbiome.Every individual’s microbiome is unique, influenced by whether he or she was born vaginally or by Caesarean section, breastfed or not, genetics, stress, infection, and the environment. Other factors that are known to affect the microbiome, that we usually have some control over, include antibiotic use, diet, alcohol consumption, smoking, and disrupted sleep.OUT OF THESE POTENTIALLY MODIFIABLE RISK FACTORS, DIET IS ONE OF THE MOST CRUCIAL COMPONENTS, WITH A SIGNIFICANT IMPACT ON THE MICROBIOME.Experiments have shown that significant changes in diet can cause large shifts in microbial composition within a single day. However, once the new diet has been discontinued, the microbial composition will revert back to its former state within 48 hours. The following are summaries of three recent studies that examined the effects of modifying diet on the microbiome, and the resulting impact on brain health and cognitive function:

• In the abovementioned review article by Dr. Francesca Pistollato and colleagues, the researchers found that nutritional interventions involving the use of probiotics and prebiotics, as well as plant-derived nutrients and phytocompounds, might stimulate the gut-brain axis in a positive manner, reduce neuroinflammation, and slow or reverse cognitive impairments associated with AD. The researchers emphasized that more research is needed, particularly involving human subjects, before recommendations about treatments with isolated elements can be made. Nevertheless, they recommend higher intakes of low-fat, plant-derived foods and lower or no intake of meat products as a general strategy that could be safely undertaken to help prevent AD.
• In 2017, Frontiers in Behavioral Neuroscience published a mini review by Dr. Emily E. Noble and colleagues about the relationship between consumption of a “Western diet,” the microbiome, and cognitive impairment. A Western diet is characterized by higher intakes of red and processed meat, refined sugars and grains, alcohol, and high-fat dairy products, with minimal intakes of fruits, vegetables, whole grains, nuts, and fish. “There is substantial evidence linking consumption of a Western diet with cognitive dysfunction,” explained Dr. Noble, a post-doctoral researcher at the University of Southern California. “Emerging evidence suggests that the gut microbiome influences cognitive function via the gut-brain axis, and that a Western diet significantly alters gut microbiota.”

Dr. Noble continued, “We discovered that there are many potential neurobiological mechanisms involved, linking consumption of a Western Diet with changes in the gut microbiome which then may be contributing to Western Diet-mediated cognitive dysfunction. For example, impairment of the blood-brain barrier may be a factor, or neuroinflammation, or resistance in insulin receptors.” Although more research is needed to fully understand the mechanisms underlying the cognitive effects of a Western diet, there is enough evidence to suggest that individuals should try to limit their intake of saturated fats and added sugars.

• In another review article, published in Neuroscience Letters in 2017, the researchers considered whether a diet that is high in fiber could improve brain health. Dr. Megan W. Bourassa and colleagues focused their research on butyrate (a short-chain fatty acid that is produced by bacterial fermentation of otherwise non-digestible fiber in the colon) and its impact on brain health. High-fiber foods that help butyrate-producing bacteria thrive include resistant starches such as whole grains and legumes, and fructo-oligosaccharides such as bananas, onions, and asparagus.

After reviewing the available evidence to date, the researchers concluded that butyrate has significant potential as a therapeutic for the brain, in dietary and pharmacologic form. The dietary form – in other words, through a high-fiber diet – is particularly appealing since it is a simple, relatively low-risk method to potentially improve outcomes for individuals with brain disorders. While butyrate offers great potential as a "treatment," more research is needed to fully understand its effectiveness as a dietary intervention.Exploration is also underway into the potential for microbiome-targeted treatments to positively impact mental health (with such treatments often referred to as “psychobiotics”).RESEARCH HAS SHOWN THAT INCREASING THE AMOUNT OF GOOD BACTERIA IN THE GUT CAN HELP INDIVIDUALS COPE WITH DEPRESSION AND ANXIETY, LOWER REACTIVITY TO STRESS, AND DECREASE NEUROTICISM AND SOCIAL ANXIETY.For example, a number of studies have found that some probiotic strains (such as Bifidobacteria, Lactobacillus, and Bacteroides) can have a positive effect on the brain and behaviour. However, substantial work is still needed before any targeted intervention can be rationally recommended.Although research has revealed interesting relationships between the microbiome and the brain, there is still much to learn. Nevertheless, there is a growing body of evidence to suggest that taking care of your microbiome is critical to your overall health, immune function, mental health, and cognitive function. There are numerous ways to keep your gut bacteria healthy and diverse, such as by consuming substantial amounts of high-fiber foods, limiting your intake of saturated fats and added sugars, only taking antibiotics when absolutely necessary, and limiting your use of antimicrobial products like hand sanitizer (wash well with soap and water instead). It is also important to make other healthy lifestyle choices, such as limiting alcohol consumption, getting enough sleep, and minimizing stress. If you take care of your good bacteria, they will help to take care of you.Source: MIND OVER MATTER V7