The importance of good bacteria in the gut has been a topic of interest for several years. A healthy gut biome is one that is diverse in good bacteria; it is essential to the body’s optimal functioning. From yogurts and fermented drinks to probiotic supplements, the health food industry is inundated with ‘good bacteria’ products. But just what are healthy bacteria, and how do they affect our bodies?
What is the Gut Microbiome?
The gut microbiome represents a community of trillions of bacteria living in the gut. These bacteria contribute to many bodily functions; they assist the body in breaking down nutrients, and have a profound impact on the immune system, endocrine system, and brain health.
The gut microbiome begins to develop at birth and is greatly impacted by early life experience. A mother’s health, delivery, and feeding method all play a great role in how an infant’s gut microbiome develops. The biome fully develops and reaches its mature state in just a few years of life. However, it can be altered by any number of outside influences. Diet, antibiotics, exercise, and geographic location can all impact the gut microbiome. The instability of the gut microbiota as well as the composition of the bacteria have been linked to a number of chronic illnesses includingmetabolic, autoimmune, neurologic and gastrointestinal diseases.
No two individuals have the same gut microbiome, and there isn’t a standard microbial makeup to compare. There is great variability in each individual and a healthy biome may look different in each person. Ultimately, a healthy gut microbiome is diverse in bacteria while maintaining its essential functions: structure, metabolic support and brain signaling. If the gut is unable to sustain essential functions, it may be deemed unstable or unhealthy.
One example of an unhealthy gut microbiome is intestinal permeability, often described as ‘leaky gut’. This occurswhen the barrier of the gut is no longer able to prevent the transmission of toxic molecules into the blood stream. This often evokes inflammatory responses in the body and can be serious.
The Gut Microbiome and the Brain
Research typically supports the concept that the gut and the brain communicate both directly and indirectly by use of the central and enteric nervous systems, endocrine and immuno-inflammatory systems, and neurotransmitters. New research in this area is allowing for the more advanced study of specific bacteria in the gut and their physiological functions. Some studies have indicated gut bacteria plays a significant role in mental health and can influence how we feel and process emotions. Researchers in Cambridge, MA study the connections between the gut microbiome and “ailments includ[ing] depression and insomnia, as well as constipation, and visceral pain like that typical of irritable bowel syndrome – conditions that may have neurological as well as intestinal components”.
Both the development of the brain and the gut microbiome are greatly influenced in early infancy, and as such, they are both equally susceptible to damage during this stage. A mother’s health and behavior are essential to a child’s physiological development. Some studies have noted the connection between severe maternal stress or illness and early damage to the gut/brain signaling of infants. Animal studies further support this, and have concluded that early life trauma has the ability to inhibit the development of the stress response system, the hypothalamic-pituitary-adrenal axis. The relationship between the stress response system and the gut microbiome is profound. The development of many neurologic and central nervous system disorders has been linked to maternal stress and infection during pregnancy. It has been suggested that these negative outcomes could be mediated by bacteria in the gut.
Several neurologic illnesses have been linked with gut issues. Autism spectrum disorders, Parkinson’s disease, and Multiple sclerosis have all been associated with altered microbiota. Risk factors for these illnesses are often associatedwith an immuno-inflammatory response.
It’s not always clear why these neurological disorders are linked with gut microbiome imbalance. In recent yearsresearchers have speculated there is a direct connection with gut balance and proteins in the brain. A study conducted in 2003 suggested that the misfolding of proteins in the brain may be responsible for the occurrence of some neurologic disorders. The misfolding of proteins can be caused by inflammation in the brain, which has been connected to altered microbiota, leading researchers to believe that these issues may originate in the gut.
The inflammation caused by an unhealthy gut has also been associated with numerous autoimmune disorders and Multiple sclerosis. Multiple sclerosis (MS) is seen most commonly in Western countries, where dietary patterns can cause inflammation and suboptimal gut health. Patients with both MS and Parkinson’s disease have found to have higher instances of intestinal permeability.
Neurodegenerative diseases like Alzheimer-type dementia as well as general cognitive decline are characterized by age-related brain changes, oxidative stress, and poor immune function. In animal studies, these factors have been shown to be directly influenced by the gut microbiome. There appears to be a link between age-related changes in the brain and age-related changes in the gut microbiota. This is illuminated by the growing awareness of connections between unhealthy eating patterns in elderly adults and the prevalence of depression.
The connection between the gut microbiome and mental health is a relatively new scientific consensus. Recent research supports the theory that many psychiatric disorders, especially depression, may be underlying inflammatory disorders. It is believed that the gut microbiome plays an important role in mediating these conditions. In rats, manipulation of the microbacteria within the gut resulted in changed behaviors related to anxiety or depression. Serotonin, a brain chemical associated with mood, anxiety, appetite, and sleep, is prevalent in the gut, and the gut microbiome has a great influence on the production of serotonin’s precursor, tryptophan. A study conducted in 2007 noted that “tryptophan, which increases brain serotonin in humans as in experimental animals, is an effective antidepressant in mild-to-moderate depression”. Given this, there is ample cause for further examination of the gut’s relationship to mental health.
Keeping the Gut Microbiome Healthy
When looking at psychiatric and neurologic illnesses, it’s hard to know what occurred first. Was it the illness or the unhealthy gut? Some experts speculate that the stress of mental illness and brain disorders is the driving factor behind the unhealthy gut. Others suggest that an unhealthy gut is responsible for the severity of poor mental health.
While there is a clear connection between the occurrence of brain disorders and an unhealthy gut microbiome, it’s not entirely clear what is responsible for the negative symptoms associated with both. However, building an understanding of the connection between brain disorders and an unhealthy gut is the first step.
Fortunately, the composition of the gut microbiome is surprisingly resilient and manageable. Adapting lifestyle and dietary patterns that may impact the gut is the first step in ensuring the microbiome is diverse and stable. Doing so will not only promote gut health, but have a positive effect on the overall health of the body. Perhaps even more encouraging, medical research has found that there are many ways to improve health without the introduction of medication.
Diet remains an important aspect of gut health. Certain nutrients like omega-3 fatty acids and zinc have proven to be important both for mental health, as well as overall physical health. The physical health benefits of consuming adequate amounts of fruits, vegetables, and whole grains is no secret. However, the Bacteroidetes found in these types of foods make them extremely beneficial to the gut, and consequently overall mental health.
There is some research to support the benefit of probiotic and prebiotic supplementation, as well as fermented food on gut health. Foods that promote gut health include probiotics (like yogurt), nondigestible carbohydrates (fiber found in fruits, vegetables, and whole grains), and flavonoid-rich produce. Because the Western diet often lacks some of these key elements, it’s not surprising that poor gut health is an associated issue. A diet heavy in fat, sugars, and refined carbohydrates can interfere with gut health and has been shown to contribute to inflammatory issues.
Exercise is not only beneficial to overall physical health, but research suggests that it can increase the diversity of the gut microbiome. It’s believed that the anti-inflammatory effects of exercise are responsible for its positive impact on gut health. In the United Kingdom, the National Institute for Health and Clinical Excellence “recommends treating mild clinical depression with various strategies, including exercise rather than antidepressants”.While physical and mental health issues can be overwhelming, it is important to remember that making small, consistent changes in lifestyle and behavior can have a very positive impact on the body. Ultimately, a healthy, well-balanced diet including a wide range of produce, whole grains, and healthy fats is a great way to positively impact gut health. Avoiding a traditional Western diet heavy in fats, refined carbohydrates, and sugars remains important in avoiding an unhealthy gut. Regular exercise and spending time outdoors is also encouraged. If one has concerns about the gut microbiome, we recommend consulting with a health care provider.