The Gut-Brain Connection: Gut Health Powerfully Influences Brain Health and Mood

Things that are happening in our gut directly affect how we think and feel. Similarly, how we think and feel directly affects the health and function of the gut. This is the gut-brain connection.

Also called the gut-brain axis, this bidirectional communication between the gut and the brain matters greatly for those of us struggling with anxiety, depression, attention disorders, and other mental health and mood issues.

It means that the food we eat, the bacteria in our gut, and the overall health of our digestive system greatly affect our thoughts, behaviors, and emotions. Understanding this important connection, it is reassuring to know that we can use diet, lifestyle, and natural medicine, including psychobiotics (probiotics that affect the brain), to simultaneously heal the gut and the mind. Brilliant!

 What is the gut-brain axis?

The gut-brain axis is the bidirectional communication between the central nervous system (the brain and spinal cord) and the nervous system of the gut (the enteric nervous system).[1] This communication links the emotional and cognitive centers of our brain with our intestinal functions.

But the gut-brain axis goes way beyond these two nervous systems. Fascinating research into the many ways that the gut and brain are connected and communicate with each other has recently exploded. We now know that gut-brain communication involves many body systems beyond the nervous system, including the hormone (endocrine) system, the immune system, the metabolic system, and the stress response system (the hypothalamic-pituitary-adrenal axis). All these systems interact with each other and with the brain to influence thoughts, behavior, and mood.

The role of the microbiota

Perhaps even more important is the recent discovery about the hugely critical role of the gut microbiota—the trillions of bacteria living mostly within the colon–play in this communication. The human gut contains more than 1,000 species and over 7,000 subspecies of microbes, mostly bacteria. The gut microbiota has such profound effects on the gut-brain axis that it is now being called the microbiome-gut-brain axis.[2]

Gut bacteria produce compounds that have direct affects in the brain. For instance, they can reduce the stress hormone, cortisol, and increase the love hormone, oxytocin. Gut microbes can also produce many different neurotransmitters, or brain chemicals, including the anti-anxiety neurotransmitter, GABA, the happiness neurotransmitter, serotonin, and the feel-good neurotransmitter, dopamine.[3]

In addition, by fermenting certain soluble fibers, the gut bacteria produce short chain fatty acids, such as butyrate. Butyrate’s important actions include preventing the gut barrier from becoming leaky and inflamed; and regulating blood sugar, immune, and nervous system functions.[2] The integrity and health of the gut lining is extremely important for keeping inflammation from reaching and harming the brain.

3 ways to improve the gut-brain connection to enhance mood

The more we learn about the complex relationship between the gut, the brain, and gut bacteria, the more researchers believe that addressing the microbiota-gut-brain connection will prove critical to preventing or treating brain disorders, including disorders like depression, anxiety, ADHD, but even Alzheimer’s and Parkinson’s diseases.[4,5]

Every week, new studies are appearing that are helping to clarify what constitutes a healthy microbiota-gut-brain axis and how we can use diet, lifestyle therapies, and supplements to address its dysfunctions.

What follows are three important things you can do to naturally enhance your gut-brain connection, along with some additional tips.

1. Increase fiber by eating a wider variety and greater quantity of plant foods.

Feed your gut microbiota with every meal by eating plants, plants, and more plants. This is the number one way to increase the diversity and abundance of gut bacteria for improving mood and brain function.

The more plants you eat, the more fiber you ingest, and the more you diversify and feed your gut bacteria so that they will increase in number. Don’t worry about the type of fiber—soluble, insoluble, fermentable, prebiotic, etc. Just focus on increasing the variety and quantity of fruits, vegetables, whole grains, legumes, nuts, and seeds you eat so that you increase your intake of all varieties of fiber.

According to gut microbiota researcher Jeff Leach, founder of the American Gut project, people who eat more than 25 to 30 different types (species) of plant foods per week have significantly greater diversity of gut bacteria.[6] He suggests eating 25 to 30 species of plants every week in order to optimize gut microbial quantity and diversity.

If you tolerate them, try to include leeks, garlic, onions, asparagus, Jerusalem artichokes, and gluten-free oats, all of which contain high concentrations of especially beneficial fibers for gut health. And don’t think this means you can’t also eat meat and fat. Just make sure you are also eating lots and lots of plant foods for fiber.

2. Avoid unnecessary antibiotics.

Because they disrupt the microbiota-gut-brain axis, antibiotics are known to increase the risk for depression and anxiety. A recent study out the United Kingdom involving hundreds of thousands of patients found that treatment with just a single course of antibiotics of any type is associated with higher risk for depression and anxiety.[7]

The risk for both conditions increased as the number of courses of antibiotics increased. For instance, for someone who has taken more than five courses of penicillin, the odds of developing depression or anxiety are increased by 56% and 44%, respectively.

Many conventional doctors prescribe antibiotics unnecessarily. Question your physician before accepting an antibiotic prescription. Consider that natural antimicrobial botanical medicines can often be used as alternatives in cases of mild infections. Even more importantly, consider that many cases which require antibiotics can be prevented with immune-supporting natural therapies.

3. Take psychobiotics.

Psychobiotics are probiotics that act as regulators of brain and behavior. There is increasing evidence that psychobiotics (probiotics) can help reduce symptoms of anxiety and depression.[8,9]

In addition to the three suggestions listed above, there are many other steps you can take to positively influence the gut-brain connection:

  • Avoid sugar, gluten, artificial sweeteners, GMO foods, and chlorinated water
  • Spend time outdoors getting dirty
  • Buy produce in farmer’s markets.
  • Practice stress reduction techniques [10,11]

[1] Ann Gastroenterol. 2015 Apr-Jun; 28(2): 203–209.

[2] Nutr Rev. 2015 Aug;73 Suppl 1:28-31.

[3] Clin Psychopharmacol Neurosci. 2015 Dec; 13(3): 239–244.

[4] Pharmacol Ther. 2015 Nov 26. pii: S0163-7258(15)00225-9.

[5] Curr Opin Clin Nutr Metab Care. 2015 Nov;18(6):552-8.

[6] High Intensity Health. Podcast #117: Jeff Leach – Human Food Project Reveals Results of Gut Bacteria on A Paleo Diet.

[7] J Clin Psychiatry. 2015 Nov;76(11):1522-8.

[8] Neuropsychiatr Dis Treat. 2015; 11: 715–723.

[9] Clin Psychopharmacol Neurosci. 2015 Dec; 13(3): 239–244.

[10] Dev Psychobiol. 1999;35:146–155.

[11] J Physiol Pharmacol. 2011 Dec;62(6):591-9.


Originally published in February 2016 and updated.

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Kathleen Jade, ND

Dr. Kathleen Jade is a naturopathic physician and served for many years as the Medical Director and Editor-In-Chief of Natural Health Advisory Institute. She has been licensed as a primary … Read More

View all posts by Kathleen Jade, ND

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