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Listen to Your Gut: Boost Brain Health With Probiotics

Updated: Nov 13, 2023

For Mental Health Awareness Month, we emphasize the importance of a healthy mind. However, did you know that the microorganisms (i.e., bacteria) in your gut have a significant impact on your mental well-being? It’s true!

The central nervous system (CNS; composed of the brain and spinal cord) and enteral nervous system (ENS; the nerve system in the gastrointestinal tract that controls movement, fluid exchange, and local blood flow; often referred to as the second brain) use a unique communicative link called the gut-brain axis (GBA) to “talk” with each other. What does this mean exactly? It means that the brain can affect intestinal activities such as signaling the release of digestive enzymes when you smell dinner cooking. The brain does this by utilizing the several-hundred-million neurons (cells that transmit signals to or from the brain) found in the gut, neurotransmitters (chemical messengers that can control feelings and emotion), hormones, immune signals, and other complex systems. However, as the GBA is bidirectional, the gut utilizes the same systems to affect the brain. The gut has been shown to affect cognition, behavior, and emotional well-being. Many researchers have noticed a link between mental disorders and gastrointestinal (GI) disorders. Initially, it was thought that conditions like anxiety and depression caused irritable bowel syndrome (or other GI-related issues). However, there is evidence that the opposite may also be true—mental wellness decreases in the presence of GI disorders.

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So, what do microorganisms have to do with anything? Well, the microorganisms in the GI tract (also called microbiota or bacteria in the gut) are intricately intertwined with GI functions. The microorganisms form a natural defense barrier and perform several metabolic, structural, and protective functions, which include synthesizing vitamins (e.g., biotin, folate) and amino acids, and forming the basis for your immune system. The bacteria in your gut fight pathogens, produce anti-microbial substances and maintains intestinal permeability (i.e., controls what can enter the body and what cannot). Also, the microbiota influences the CNS directly as researchers believe that the gut bacteria can control the structure and functions of neurons.

The healthy functioning of the body and brain requires a careful balance of bacteria. There are hundreds of different types of bacteria in the GI tract. All play different roles that are not entirely understood. However, studies have shown that certain diseases are associated with an increase in some bacteria and decreases in others. For example, depression is associated with lowered levels of the Bifidobacterium and Lactobacillus bacteria, but heightened levels of Bacteroidetes, Proteobacteria, and Actinobacteria. This leads researchers to conclude that dysbiosis (i.e., the imbalance of bacteria) can increase the incidence of specific mental disorders, including depression, anxiety, autism, and other conditions. The balance of microorganisms influences the health of the gut, and thus the gut influences the health of the brain. What does that mean for you?

You may have control over the balance of microorganisms in your gut! The types of bacteria you acquire are influenced by diet, lifestyle, drug use (e.g., antibiotics), and other environmental factors. Scientists and healthcare professionals may suggest improving the balance of bacteria (to treat diseases) through the use of probiotics (“good bacteria”). Studies show that more microbe diversity in the gut is the key to balance. You may have heard of probiotic pills, but healthy bacteria can be easily found in foods as well.

photo credit: Cleveland Clinic

Great sources of plant-based probiotic foods include:

  • fermented veggies like sauerkraut or kimchi

  • fermented soy products like miso or natto

  • fermented tea (i.e., kombucha)

  • Fortified dairy alternatives (i.e., soy or nut-based kefir or yogurt)

There is one caveat, however — in order for the healthy bacteria in the fermented foods to do their job by increasing diversity in your gut, they need dietary fiber. Consuming a wide variety of plant-based foods can ensure that you get various types of fiber that various types of bacteria species like to consume.

Prebiotic fiber is nondigestible fiber that acts as food sources for healthy bacteria or probiotics. Probiotics are living things, and like all living things, they cannot survive without food. That is one reason why it is so vital to eat fibrous foods like fruits, vegetables, beans, peas, lentils, nuts, seeds, and whole grains. Your body does not contain digestive enzymes to digest fiber, therefore it's instead instead is broken down by your gut bacteria (in a process called fermentation), allowing good bacteria to flourish. A minimum of 25 grams of fiber a day for women and 38 grams of fiber per day for men is recommended, but some individuals who eat all plant-based get up to 75 grams of fiber a day or more!

Recommendation: Understand how much fiber you're currently consuming before adding a lot of fiber to your plate. You can do this by using an app, like Cronometer or MyFitnessPal, to calculate how much fiber you're getting in a day. Slowly increasing your fiber intake by 5–10 grams a week will help your body adjust to the increasing fiber and avoid gastrointestinal discomfort. Also, remember to drink plenty of water to help pass the fiber through.

Great sources of prebiotic fiber include:

  • Bananas

  • Onions

  • Garlic

  • Leeks

  • Asparagus

  • Artichokes

  • Beans

  • Oats

  • and many more! Consuming a wide variety of plant-based foods can ensure fostering a healthy gut microbiome.

photo credit: Irena Macri

There is still much we do not know about the gut-brain axis, the role of GI microorganisms, and the benefits of probiotics. Until more evidence is acquired, probiotics in any form should not be considered a reliable therapy to treat illnesses. Probiotic foods are generally safe and are part of a healthy diet. However, if you are interested in consuming probiotics to improve your health, consult your doctor or health professional for guidance (especially if targeting a specific condition).

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Greetings! My name is Mary Pittman. I am currently enrolled in Georgia State University’s Coordinated Nutrition Program. Someday soon, I will be a registered dietitian with a Master’s degree! I have worked in a hospital for six years, four of which were in the ICU. I have worked with hundreds of patients and have seen many illnesses. Many illnesses can be treated and prevented by a healthy lifestyle. It is my dream to learn how to help people who struggle to find a healthier way to live. My other interests include painting, playing my violin, and learning Harry Potter trivia (sorry, not sorry).


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