How Your Gut Can Keep Your Brain Healthy

The "gut" refers to the entire gastrointestinal tract and all associated structures that play a role in the digestion, absorption, and excretion of food. Over the past several years we have begun to learn more and more about how important gut health is and it's implications on overall health. The environment of the gut is known to be crucial for proper brain health and the prevention of certain neurological diseases in the brain. More specifically, the "gut microbiota" may be the key regulator in the association between the gastrointestinal tract and the brain. 

What is the gut microbiota?

The gut microbiota is also known as the the gastrointestinal microbiota, gut flora, or microbiome. It is a complex network of trillions of living microorganisms like bacteria, archaea, and eukarya that are found throughout the gastrointestinal tract. These microorganisms are crucial for proper health of the gut. When healthy, the microbiota is very beneficial in regulation of the immune system and digestion of foods. The organisms in the microbiota feed off of resistant starch and fermentable fibers, which go undigested until it is the microbiota's turn to metabolize them. Throughout this process the microbiota creates certain gases, vitamins, and hormones that are essential for brain health. In addition to brain health, dysregulation of the microbiome has been correlated with many autoimmune and inflammatory conditions. 

What Is The Gut-Brain Axis:

Years ago, the effect of the gut on the brain was only acknowledged in disease processes where infectious organisms were ingested and later crossed the blood-brain-barrier. However, somewhat recent evidence indicated that altering the gut microbiota may prevent and cure brain diseases which lead to further investigation by scientific studies. In 2013, the National Institute of Mental Health launched a project to explore the relationship between the gut and brain health. The knowledge and research of this connection has exponentially grown since. 

The gut-brain axis AKA gut-microbiota-brain axis refers to a communication network that allows the brain and the microbiota to "talk" to each other. This network of communication also includes other systems involved in immunity, hormonal signaling, and the autonomic nervous system ("fight or flight"/"rest and digest"). The communication of the gut-brain axis is bi-directional which means that the health and actions of the gut can affect the brain as well as vise versa. For example, a normal gut microbiota has been shown to affect brain health (1), and poor brain health like stress and depression has been shown to alter gut function and it's microbiota (2) (3). Although the gut-microbiota-brain axis is bi-directional, more emphasis is placed on the gut portion because it can be easily controlled through interventions (3). The mechanism of this bi-directional communication is mostly due to neurotransmitters, hormones, and the action of the vagus nerve. Health of the gut-brain axis begins at birth as the diversity of the bacteria in the gut has been shown to be critically important in the development of body systems including the central nervous system (4). A dysfunctional microbiota and gut-brain axis is associated with overall brain health as well as many cognitive and neurological conditions such as the following:

• depression (5)

• anxiety (5)

• obsessive-compulsive disorder (6)

• autism spectrum disorder (7)

• Parkinson's disease (8)

How to keep a healthy gut microbiota

Your gut microbiota is a great representation of your life story and has developed based on genetics and exposures to certain microorganisms throughout your entire life. Factors such as breast feeding vs. bottle feeding and your first introduction to food play a very important role about how your microbiota will develop for your entire life. At this point it is impossible to change those early post-natal factors but there are still things you can be doing today to optimize your gut microbiota:

1. Limit artificial sweeteners

Among many other negative health consequences, large consumption of artificial sweeteners can have negative effects on the gut microbiota. Studies have linked dysfunctional metabolic processes like glucose intolerance caused by artificial sweeteners to the negative effect they have on the make up of the gastrointestinal microbiota (9). Avoidance or strict limitations of artificial sweeteners is a good strategy to preserve a healthy gut. 

2. Eat a wide variety of foods

A diverse gastrointestinal microbiota is generally recognized as a healthy one. One way to improve the diversity of the gut is to eat a wide variety of foods. Different strains of organisms in the gut feed off of different foods and it is important to provide this food for each strain through a diverse diet. Eating a wide variety of plants, meats, and healthy fats is an excellent strategy and has been shown to rapidly improve the make-up of the microbiota (10,11). 

3. Eat plenty of Fruits, vegetables, and nuts

Fiber is a very important factor in maintaining a healthy gut due to its ability to serve as food for the microbiota. Most vegetables are a great source of fiber and can provide this food to keep a diverse and healthy microbiota (12). A diet high in fruits, vegetables, and nuts has been shown to prevent the growth of bad infectious bacteria (13) and increase the growth of healthy bacteria (14, 15). 

4. Eat fermented foods

Fermented foods are foods that are changed by microbes and include yogurt, kimchi, sauerkraut, kombucha, and kefir. These foods usually contain many beneficial strains of bacteria to keep your gut healthy. People who eat these foods have been shown to have more healthy and less disease causing bacteria in their gut (16). 

5. Take a probiotic supplement

Probiotic supplements contain live microorganisms, which are usually similar to the bacteria found in the gut. Although probiotic supplement may not benefit people with a healthy gut, they have been shown to improve the composition of the microbiota when it becomes compromised (17). This shows that probiotics may be an important tool to use during sickness or antibiotic use to help rebuild a healthy gut.

Overall, the understanding of the gut-microbiota-brain connection is in its infancy and there is plenty more to be discovered. Research on this topic is being published at a very rapid rate and much of it is subject to change or become more solidified. There is no doubt that there is an important link between gut and brain health with many implications on treating and preventing neurological disease. There are many natural dietary strategies that can be done now to ensure a healthy microbiota and optimize brain health.