How to Maintain Gut Health to Improve Brain Function
The three main causes of death in the United States are heart disease, cancer, and stroke.1 Rates of obesity and diet-related chronic diseases in the United States are higher than ever. About half of all American adults have one or more chronic diseases that are related to poor quality diet and gut health.2 The Western diet consists of highly processed and preserved foods, sterilized of all beneficial probiotics and prebiotics. These foods play a significant role in promoting diet-related diseases and poor gut health.
It’s obvious that consumers need to make healthier life choices when it comes to the quality of their diet and the frequency of their exercise to prevent many types of chronic disease. To understand why diet has such a great impact on our health and what changes we must make, we have to understand our second brain, the gut microbiome.
The Microbiome and the Gut-Brain Axis
In the human gut, there are up to 100 trillion bacteria, their identity determined from the moment of birth. The microbiome develops with age, as environmental stimuli and food are variable. The microbiome consists of over 100 times more genes than the entire human genome!3 It is becoming increasingly clear that these microbes are required for normal brain development as well as brain function in adulthood.
Our gut microbiome is essential for digestion and nutrient absorption from the food we consume. They produce energy that is otherwise inaccessible to us by breaking down soluble fiber. These microbes also produce vitamins such as biotin, folate, and vitamin K, prevent pathogen accumulation, and aid in the development of our immune system.4 The gut microbiome composition seems to be more influenced by diet and environmental factors rather than genetic factors which is fortunate since we can’t change our genetics
From “Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions”. Click here for the full image
The gut-brain axis consists of a bidirectional communication system between the central nervous system and the gastrointestinal tract.5 This relationship connects the emotional and cognitive centers of the brain with the functions of the gut. We don’t really understand the complexity of the gut-brain axis system yet but we are able to observe some of its impacts on the overall health of individuals.
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An Unhealthy vs. Healthy Microbiome
A healthy microbiome is defined by the diversity and abundance of the native microbes in the gut, which is a state called eubiosis. Whether the abundance of just specific types of microbes or the abundance of all microbes is best for us remains unclear. Considering that these microbes aid in the absorption of nutrients and the establishment of our immune system, it makes sense that a lack of diversity and abundance can result in inflammation. This unhealthy state is termed dysbiosis.
Dysbiosis is a condition related to illnesses such as celiac disease and inflammatory bowel disease, obesity, metabolic disorder, cardiovascular syndrome, allergy, and asthma.7
Disruption of the gut microbiome in humans is associated with the development of various diseases and inflammation. Through the gut–brain axis system, the gut microbiome inﬂuences neural development, cognitive function, behavior, anxiety, and depression.5
Possible Causes of Dysbiosis
- Lack of diversity and quality of foods
- Processed and refined foods
- Use of antibiotics
- Lack of probiotics and prebiotics
- Clinical practices such as C-sections
- Not breastfeeding (affects the infant)
- Environmental toxins
Inflammation is associated with a wide range of disorders, thought to be triggered by an inflammatory immune response from the gut to the brain. Alterations to the gut microbiome have been observed to play a key role in promoting inflammatory bowel conditions which can increase the risk of mental disorders. These conditions are observed to be more prevalent in females than in males, with the highest rates being in the western parts of the world. This then suggests that environmental exposures, diet, and alterations to the gut microbiome have a great influence on inflammatory bowel conditions.6
Some interesting findings on this
- Hadza hunter-gatherer individuals were found to possess higher levels of microbial abundance and biodiversity compared to Italian urban controls.8
- Stress caused the gut microbiota of lean female mice to more closely resemble that of obese female mice, suggesting microbial changes may depend on sex.9
- A study on a large population reported that treatment with a single antibiotic was associated with an increased risk for depression and anxiety, rising with multiple exposures.10
- Obesity and obesity-related metabolic disorders are characterized by specific alterations in the composition and function of the human gut microbiome.11
How to Maintain a Healthy Microbiome
Prebiotics and Probiotics
Prebiotics are functional foods that are indigestible in the upper gastrointestinal tract that stimulate growth of gut microbes. Studies have shown that pure prebiotics increase beneficial gut bacteria. Galactooligosaccharides are prebiotics that have been shown to promote the growth of beneficial microbes that improve lactose digestion and tolerance in individuals who are lactose intolerant.12
Probiotics are live microbes that can benefit the gut by increasing the diversity and abundance of microbes. They are likely to replace pathogenic bacteria and promote a rebalancing of the microbiome to prevent gut inflammation and other diseases.13
Fibers have been observed to provide substrates for microbial growth, allowing microbial species that are able to utilize these substrates to expand their populations. The average fiber intakes for U.S. children and adults are less than half of the recommended levels.8
High intakes of dietary fiber are associated with a lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases .8 Increased fiber intake has been observed to ease certain gastrointestinal disorders and enhance immune function.8
Exposure to stress has been shown to alter the profile of the microbiome, reducing diversity and promoting inflammation. Inadequate sleep increases the risk of age-related cognitive decline. Partial sleep deprivation alters the human gut microbiome, and its composition is associated with cognitive flexibility in animal models.14
Overall, the microbiome remains mysterious to us in many ways but it is evident that it is incredibly crucial to maintain a healthy microbiome to improve our brain function and to increase longevity. By making changes to our diet and managing our sleep and stress, we can reverse the damages done to our gut in order to become healthier individuals. Understanding the microbiome has very promising applications such as developing therapeutics for those suffering from diseases related to dysbiosis.
For a more detailed article on the microbiome, check out the article “The Microbiota-Gut-Brain Axis: What, Why, and How to Maintain Gut and Brain Health” by Straight From a Scientist!
- Christopher, J. L.; Danaei, G.; Ding, E. L.; Mozaffarian, D.; Taylor, B.; Ezzati, M. The Preventable Causes of Death in the United States : Comparative Risk Assessment of Dietary , Lifestyle , and Metabolic Risk Factors. 2009, 6 (4). https://doi.org/10.1371/journal.pmed.1000058.
- Raghupathi, W.; Raghupathi, V. An Empirical Study of Chronic Diseases in the United States : A Visual Analytics Approach to Public Health. 2018, 10–12. https://doi.org/10.3390/ijerph15030431.
- Qin, J.; Li, R.; Raes, J.; Arumugam, M.; Burgdorf, S.; Manichanh, C.; Nielsen, T.; Pons, N.; Yamada, T.; Mende, D. R.; et al. Europe PMC Funders Group Europe PMC Funders Author Manuscripts A Human Gut Microbial Gene Catalog Established by Metagenomic Sequencing. 2013, 464 (7285), 59–65. https://doi.org/10.1038/nature08821.A.
- Rossi, M.; Amaretti, A.; Raimondi, S. Folate Production by Probiotic Bacteria. 2011, 118–134. https://doi.org/10.3390/nu3010118.
- Rogers, G. B.; Keating, D. J.; Young, R. L.; Wong, M.; Licinio, J.; Wesselingh, S. From Gut Dysbiosis to Altered Brain Function and Mental Illness : Mechanisms and Pathways. 2016, 21 (6), 738–748. https://doi.org/10.1038/mp.2016.50.
- Haro, C.; Rangel-zú, O. A.; Alcalá-díaz, J. F.; Gómez-, F.; Pérez-martínez, P.; Delgado-lista, J.; Quintana-, G. M. Intestinal Microbiota Is Influenced by Gender and Body Mass Index. 2016, 1–17. https://doi.org/10.1371/journal.pone.0154090.
- Gagliardi, A.; Totino, V.; Cacciotti, F.; Iebba, V.; Neroni, B.; Bonfiglio, G.; Trancassini, M.; Id, C. P.; Pantanella, F.; Schippa, S. Rebuilding the Gut Microbiota Ecosystem. 2018. https://doi.org/10.3390/ijerph15081679.
- Makki, K.; Deehan, E. C.; Walter, J.; Bäckhed, F. Review The Impact of Dietary Fiber on Gut Microbiota in Host Health and Disease. Cell Host Microbe 2018, 23 (6), 705–715. https://doi.org/10.1016/j.chom.2018.05.012.
- Bridgewater, L. C.; Zhang, C.; Wu, Y.; Hu, W.; Zhang, Q.; Wang, J.; Li, S.; Zhao, L. Gender-Based Differences in Host Behavior and Gut Microbiota Composition in Response to High Fat Diet and Stress in a Mouse Model. Sci. Rep. 2017, No. August, 1–12. https://doi.org/10.1038/s41598-017-11069-4.
- Laurie, I.; Yu-Xiao Yang; Haynes, K.; Mamtani, R.; Boursi, B. Antibiotic Exposure Associated with Increased Risk for Depression, Anxiety. 2015, No. November.
- Davis, C. D. The Gut Microbiome and Its Role in Obesity HHS Public Access. Nutr Today 2016, 51 (4), 167–174. https://doi.org/10.1097/NT.0000000000000167.
- Intestinal, G. U.; Azcarate-peril, M. A. Prebiotics for Lactose Intolerance : Variability In. 2018. https://doi.org/10.3390/nu10101517.
- Hemarajata, P.; Versalovic, J. Effects of Probiotics on Gut Microbiota : Mechanisms of Intestinal Immunomodulation and Neuromodulation. 2013, 39–51. https://doi.org/10.1177/1756283X12459294.
- Anderson, J. R.; Carroll, I.; Azcarate-peril, M. A.; Rochette, A. D.; Heinberg, L. J.; Peat, C.; Steffen, K.; Manderino, L. M.; Mitchell, J.; Gunstad, J. A Preliminary Examination of Gut Microbiota , Sleep , and Cognitive Fl Exibility in Healthy Older Adults *. Sleep Med. 2017, 38, 104–107. https://doi.org/10.1016/j.sleep.2017.07.018.
Good article; small typo: “effects the infant”. Shouldn’t be “affects the infant”.
Lol, literally typo’d my comment about a typo. Shouldn’t it BE “affects the infants”.
You’re absolutely right! I fixed it. Thank you for catching that (:
Great read! Very resourceful!
“Alterations to the gut microbiome have been observed to play a key role in promoting inflammatory bowel conditions which can increase the risk of mental disorders”.. How high is the risk? There is not enough strong evidence to suggest a possible models of care change in treating people with mental disorders. In the years of treating mental health patients, gut microbiome has little to do with what exacerbates their condition.
Inflammatory bowel conditions have been observed to increase the risk of mental disorders. Over 30% of patients with inflammatory conditions experience increase depression and anxiety which in turn can increase risks of developing mental disorders, especially in aging patients. I never said that gut dysbiosis itself causes the disorders. Gut dysbiosis itself triggers inflammation which in turn can lead to many issues in the body, particularly in the brain. In one study, the administration of a specific short-chain galactooligosaccharide significantly improved lactose digestion and tolerance in human subjects, thus reducing inflammation. Fecal transplants are being conducted to relieve patients from inflammatory bowel conditions, especially Crohn’s disease, and great success has been observed. The keyword is “can” and not “does”. Many studies have linked gut dysbiosis to mental disorders but exactly how is unknown. The microbiome plays an important role in programming the hypothalamic-pituitary-adrenal axis and stress reactivity. The microbiome has also been found to be involved in specific age-related illnesses such as Alzheimer’s disease and Parkinson’s disease were patients were observed to have a less diverse microbiome with distinct compositional differences compared with the healthy microbiome. The gut-brain axis affects mood disorders through multiple systems, including the neuroendocrine system. It is not standard practice to treat disorders by focusing on the microbiome and it is not standard practice to even consider gut dysbiosis as a potential cause to any condition being evaluated. Common practices are to make a generalized diagnosis along with a prescription of some sort of drug. The microbiome can be a viable therapeutic target to treat or reduce psychiatric symptoms but, as I mentioned, it is rarely ever brought up or even seriously considered. The field is growing quickly and attracting a lot of attention due to its promises and I hope we can find therapeutics to help ease the patients’ pain.