Two Brains? The Answer to Treating My Depression May Be in my Gut

Mar 3, 2020
Image of a torso with the digestive system highlighted and a head with the brain highlighted

“Our two brains ‘talk’ to each other, so therapies that help one may help the other. In a way, gastroenterologists (doctors who specialize in digestive conditions) are like counselors looking for ways to soothe the second brain.” – Jay Pasricha, MD, director of the Johns Hopkins Center Neurogastroenterology, explaining the gut-brain connection.

All of us feel sad or down sometimes. These feelings may be the result of life circumstances, from a lost job to the death of a close family member or friend. Other times we are not clear why we feel sad—we may have a genetic vulnerability to depression, faulty mood regulation by the brain, or even a chemical reaction to specific medications.

For some of us, the feelings of sadness lift quickly. Sometimes we have a “perfect storm” of several factors coming together to lead us into a major depression.

No matter what the cause, depression can change the course of our lives if it doesn’t get better. We may lose interest in our jobs, our relationships, and stop doing most activities that used to give us joy, from family outings to hobbies. We may even begin to feel life isn’t worth living.

At this point, it may be time not only to seek help from a health professional, but also to examine our diet and lifestyle. Both affect the bacteria in our digestive system—the gut microbiome. By understanding how these bacteria, or the “second brain” can impact our thoughts, moods, and even behavior, we can make diet and lifestyle changes that can put us on a path to better mental health and help us feel hope again.

What is persistent depression? Why we can’t “just snap out of it.”

Image of a man standing alone facing a vast sea

After a major family illness, event, or death, our boss or friends are probably sympathetic—for a while. If sadness persists and we continue to show little interest in jobs, relationships, or in the activities we used to enjoy, friends or family members may tell us to join a gym, take a class, eat more greens, or “snap out of it”; the suggestions are varied but equally unhelpful.

If the depression continues, life can quickly change course. An employer may let us go, and personal relationships may permanently falter.

What many well-meaning family members or friends don’t understand is that a major depressive disorder or clinical depression is not a weakness or a lifestyle choice. Rather, it is a disabling illness that affects about 17.3 million adults in the United States each year. This number represents 7.1% of all U.S. adults.

Worldwide, about 300 million suffer from depression, making it the leading cause of disability, according to WHO statistics. Every 40 seconds someone loses their life to suicide.

Depression and cognitive decline: a public health crisis

In a Fortune Magazine commentary on World Mental Health Day, Arianna Huffington calls the impact of depression a public health crisis “so huge and so daunting, it’s easy to feel paralyzed and helpless.”

The Economic and Social Impact of Depression

Key findings from the Impact of Depression at Work Audit (Center for Workplace Mental Health):  The effects of depression contribute to the estimated $100 billion annual cost of depression for U.S. employers, including $44 billion a year in lost productivity alone.

  • Mental illness short-term disability claims have grown by 10% annually.
  • Nearly a quarter (23%) of a panel of U.S. workers and managers in a survey indicated they have received a diagnosis of depression at some time in their life.
  • Two in five of those respondents (40%) reported taking time off from work—an average of 10 days a year—as a result of their diagnosis.

One reason for the high level of disability is that not only is our emotional response affected; depression can cause significant cognitive changes— the mental process of “comprehension, judgment, memory, and reasoning,” as defined in the Psychiatric Glossary of the American Psychiatric Association. Even more alarming, some studies have shown that cognitive impairment may continue even after the depression is treated, and the emotional symptoms improve.

Another disturbing aspect of depression is the link to dementia, which has been documented in numerous studies. For example, according to a 2015 study in JAMA Psychiatry, people with depression had an 83% percent increased risk of acquiring dementia compared with people who did not have depression.

In the same study, researchers found that people who had depression and type 2 diabetes had a 117% increased risk of developing dementia.

With the sheer number of aging adults all around the world, depression and dementia will be the “top public health crisis,” according to an article by four former surgeons general.

Communities of color are especially affected. By 2050, 14 million people are projected to live with dementia, and by 2030, nearly 40% of Americans living with dementia will be Latino or African American. The surgeons agree depression is one of the major risk factors.

When bare survival is impossible: the danger of suicide

With clinical depression, anything beyond bare survival may feel impossible. If the pain of depression is severe enough, continuing to live becomes too difficult for some. About 60% of suicides had symptoms of major depression.

Rising Suicide Rates for General Population

  • Suicide rates have gone up in every state from 1999 to 2016.
  • Suicide is the 10th leading cause of death 
  • Over 40,000 people die by suicide each year in the United States.

Call the toll-free National Suicide Prevention Lifeline (NSPL) at 1-800-273-TALK (8255), 24 hours a day, 7 days a week. The service is available to everyone. The deaf and hard of hearing can contact the Lifeline via TTY at 1-800-799-4889. All calls are confidential.

Suicide and Veterans, according to the VA National Suicide Data Report:

  • About 20.6 veterans commit suicide every day.
  • There were more than 6,000 veteran suicides each year from 2008 to 2016.

For veterans in crisis or their families, free, confidential support is available 24/7. Call the Veterans Crisis Line at 1-800-273-8255 and Press 1, send a text message to 838255, or chat online. A list of Supports for Veterans is in the Reference section, at the end of the blog.

However, no matter how painful and disabling the depression we may feel, there is hope!

Treatments are available that have helped millions to overcome depression. The first step is to be evaluated. According to the CDC, the following are just a few of the symptoms that tell us it may be time to seek help from a health professional:

  • Are you feeling sad or anxious often or all the time?
  • Have you lost interest in activities that you used to enjoy?
  • Do you have problems falling asleep or are you sleeping too much?
  • Do you have aches and pains and stomach problems that don’t go away?
  • Do you feel tired all the time, even after sleeping enough?

If you feel worthless, helpless, or feel life isn’t worth living anymore, it is definitely time to find help!

Treatments for depression

Image showing the gut brain axis

After our health practitioner determines we are depressed, traditional treatment can include medication, psychotherapy, and electroshock therapy. In the last decade, researchers have found that changing the gut bacteria in the gut microbiome—the trillions of bacteria, fungi and other microbes that live in our intestinal tract—may be also be a viable treatment strategy for diseases like depression.

Why is my gastrointestinal tract my “second brain”?

We already understand that if we are nervous about something or worry, we often feel stomach pain, cramping, constipation, or we may lose our appetites entirely. Stress and depression can also lead to more serious conditions like ulcers and irritable bowel disease (IBD).

What we may not realize is that this link between our gut and brain goes both ways. Neuroscientists are finding that the gastrointestinal tract is acting as a “second brain” because it contains so many nerves that send signals back and forth to the brain—which can impact our physical health, our mood, and even the way we think.

This “other” brain is hidden in the walls of the digestive system—two thin layers of more than 100 million nerve cells lining our gastrointestinal tract from esophagus to rectum called the enteric nervous system (ENS).

The main role of the ENS is to control digestion, from swallowing, to the release of enzymes that break down food, to nutrient absorption, and elimination.

While the ENS doesn’t directly help us write our wedding vows or learn a new language, it does send signals to our “big brain” that can trigger mood changes, which can shape our behavior.

“The enteric nervous system doesn’t seem capable of thought as we know it, but it communicates back and forth with our big brain—with profound results.”

– Jay Pasricha, MD, Director of the Johns Hopkins Center for Neurogastroenterology in “Johns Hopkins Medicine, The Brain-Gut Connection

The vagus nerve—our own stairway to heaven

The gut and the brain are in constant communication. Researchers have found that gut bacteria produce 90% of the well-known brain chemical serotonin, which regulates mood and appetite. In fact, a major European study with 2,000 participants determined over 90% of the bacteria in the gut are capable of producing neurotransmitters (chemical messengers to the brain).

The lead researcher of this study, microbiologist Jeroen Raes of the Catholic University of Leuven in Belgium, explains this ability to send chemical signals to the brain is not found in bacteria outside of the microbiome in a February 5, 2019 article in

“It feels like an evolutionary adaptation to the symbiosis of bacteria and [humans],” says Raes. “If you start thinking about that, then your head explodes. Bacteria live within us and have found all these ways to communicate with us and potentially influence our behavior.”

The vagus nerve is one of the major nerve pathways in this gut-brain-axis. Back to those busy bacteria. Their chemical signals stimulate the vagus nerve, which rushes information to various brain regions such as the hypothalamus (with controls many essential functions, from body temperature, thirst, and appetite, to emotions, sleep cycles, and the sex drive).

Researchers have found that gut bacteria produce 90% of the well-known brain chemical, serotonin, which regulates mood and appetite. In fact, a major European study with 2,000 participants determined over 90% of the bacteria in the gut are capable of producing neurotransmitters (chemical messengers to the brain).


No surprise then that the type of bacteria in our gut can have a major impact on how our brains function. A gut microbiome with a healthy mix of bacteria may help us to stay active, more productive, and happier. A microbiome with increased undesirable bacteria is linked to depression and a wide range of mental and physical health conditions.

But it is important to remember that the gut-brain-axis runs both ways. While the bacteria in our gut can influence our mood and general health, stress, trauma, and life circumstances can also change the type of bacteria that dominate in the gut, which can lead to depression and other health conditions.

How to Improve my Microbiome

Why should I care about research with obese mice?

Numerous animal and human studies have demonstrated the link between the bacteria in the gut microbiome and depression and anxiety. Let’s start with a 2018 study at Harvard Medical School’s Joslin Diabetes Center.

Joslin scientists found that mice that become obese when put on a high-fat diet showed significantly more signs of anxiety, depression, and obsessive behavior than animals on standard diets.

The senior researcher on the project, C. Ronal Kahn, MD, explains in the related news release:  “What this study says is that many things in your diet might affect the way your brain functions, but one of those things is the way diet changes the gut bacteria or microbes. Your diet isn’t always necessarily just making your blood sugar higher or lower; it’s also changing a lot of signals coming from gut microbes and these signals make it all the way to the brain.”

When researchers changed the diet back, the anxiety and depression symptoms were reduced or reversed in the mice. Kahn confirms that “this proves that these behaviors are driven to some significant extent by the gut microbiome.”

The team also linked alterations in the microbiome to the production of certain neurotransmitters—the chemicals that transfer signals across the brain. Going forward the team will identify specific populations of bacteria involved in these processes, and the molecules that the bacteria produce. This information will contribute to the identification of specific supplements or drugs to produce a healthier microbiome—and reduce symptoms of depression and anxiety.

The condition of my colon has me down…

This link between the condition of the colon and depression is also confirmed by numerous studies with humans. For example, researchers found that symptoms of depression dropped significantly among a group of young adults after they followed a Mediterranean-style pattern of eating for three weeks. Participants saw their depression “score” fall from the “moderate” range down to the “normal” range, and they reported lower levels of anxiety and stress too.

Alternatively, the depression scores among the control group of participants — who didn’t change their diets — didn’t budge. These participants continued to eat a diet higher in refined carbohydrates, processed foods, and sugary foods and beverages. Their depression scores remained in the “moderate severity” range.

Are my prescription medications making me depressed?

The drugs we take can also have a major impact on the microbiome that can lead to depression. Studies have shown that even one course of antibiotics can damage the ecology of the gut microbiome and raise risk of depression.

In a recent JAMA study, researchers found that one in three Americans are taking other drugs on a daily basis that can lead to depression. The researchers examined results from the National Health and Nutrition Examination Survey. For the survey, 26,192 adults listed the medications they were taking at the time of the survey and completed a depression screening test.

image showing many pills in a pile

The study authors noted that over 200 common drugs list depression as a possible side effect. These include common drugs like Prilosec or Zantac for acid reflux, beta blockers for high blood pressure, Xanax for anxiety, anti-convulsant drugs, and even painkillers like ibuprofen.

Many people take multiple medications like these. In a press release about the study, lead author, Dima Mazen Qato, assistant professor at the College of Pharmacy of the University of Illinois, Chicago, notes that as we take more drugs on a daily basis, we also face increasing rates of depression, anxiety, and suicide.

She suggests that health care providers consider the role these drugs play in depression in their decision to prescribe them.

Can my daily walk make a difference?

Yes! A January 2018 New York Times article, “Exercise Alters Our Microbiome. Is That One Reason It’s So Good for Us?” focuses on the work of scientists from the University of Illinois at Urbana-Champaign. The researchers recruited 32 men and women who did not exercise. About half were obese and the rest of normal weight.

During the six weeks of the study, the men and women began supervised workouts. They started with 30 minutes of easy walking or cycling and increased to an hour of vigorous jogging or pedaling. They did not change their diets.

The results? There were definite changes in the microbes that populate the gut microbiome. The bacteria that produce desirable short-chain fatty acids (SCFA), especially butyrate, increased. SCFA are associated with reduced disease risk and improvements in brain health.

Without exercise, the gut microbiome returned to the pre-study condition.

In a January 2019 study in JAMA Psychiatry, a team led by Massachusetts General Hospital (MGH) investigators also found strong support that physical activity is a preventive measure for depression.

What can I eat to reduce the risk for depression?

Limit foods that feed undesirable colonies of bacteria. Some of the main culprits:

  • Processed foods
  • Processed meats
  • Fried foods
  • Potatoes and refined grains, such as white bread and pasta
  • Sweets like cake, cookies, and sodas
  • Salt and dairy fats
  • Alcohol

As bad bacteria flourish, they release chemicals that may lead to inflammation, which weakens the gut wall. When the intestinal wall allows toxins to seep into the body from the gut, (“leaky gut syndrome”), these toxins may be causing an immune system response—inflammation, which can impact mental health. For more information on inflammation and disease risk, check out our Men’s Health Month blog.

Fiber rich foods, especially those high in prebiotic fiber and fermented foods provide a big boost to gut health. They nourish beneficial bacteria that keep the barrier between the colon and the rest of the body strong to prevent toxins from moving into the bloodstream.

Foods high in prebiotic fiber include:

  • Chicory root
  • Asparagus
  • Jerusalem artichoke
  • Leeks and onions
  • Oatmeal, flax, and barley
  • Cruciferous vegetables, such as broccoli, Brussels sprouts, kale, and cauliflower
  • Fruits like apples, bananas, raspberries, and blueberries


Image of healthy fruits and vegetables

Foods with live probiotic bacteria are also beneficial. Good choices include:

  • Fermented vegetables like kimchi or sauerkraut
  • Fermented soybeans (miso)
  • Kombucha tea
  • Kefir
  • Plain yogurt

That food impacts our mental health was confirmed in a recent study where scientists examined data on nearly 46,000 people. The team searched through major electronic databases up to March 2018 for all randomized controlled trials of dietary interventions reporting changes in symptoms of depression and/or anxiety in clinical and non-clinical populations.

The analysis revealed that every kind of dietary improvement “significantly reduced depressive symptoms.”

How can Prebiotin help me keep my microbiome healthy?

Most Americans don’t get the recommended daily fiber allowance, upwards of 25 grams per day for women and 35 grams a day for men, in their daily diet. A medically-researched prebiotic supplement like Prebiotin can be an excellent source of daily prebiotic fiber so we get enough for optimal health.

Prebiotin® Prebiotic Fiber is an especially rich, chicory root-based source of prebiotic fiber that contains inulin and oligofructose. These two types of fiber (oligofructose-enriched inulin or OEI) are fermented throughout the colon and nourish beneficial bacteria like bifidobacteria and lactobacilli.

As these highly favorable bacteria flourish, they generate more beneficial short chain fatty acids (SCFAs). One SCFA, butyrate, can be especially effective in reducing the inflammation from leaky gut syndrome that is linked to mental health conditions like anxiety and depression.

Focusing on gut bacteria to reduce depression risk and symptoms

The evidence linking gut health and depression grows each day. We can make a difference in our mental health—and cognitive abilities—by taking steps to improve our gut health, from daily exercise, to watching the prescription drugs we take, and eating fiber-rich foods. We can also add a clinically-researched prebiotic fiber like Prebiotin to help friendly bacteria flourish.

The importance of nourishing the right bacteria in our “second brain” to improve depression and other mental health conditions is summed up succinctly in a 2015 article in The Lancet Psychiatry:

Evidence is steadily growing for the relation between dietary quality (and potential nutritional deficiencies) and mental health, and for the select use of nutrient-based supplements to address deficiencies.” The Lancet Psychiatry

If you are experiencing depression, you are not alone. There are numerous resources that can offer support and help in getting better. Resources are listed below. For a complete list of resources, please follow the link for Everyday Health.

There is always hope!

Depression and Coronavirus

Maintaining a healthy microbiome is especially important during the coronavirus pandemic. Forced isolation, job loss, financial insecurities, and the daily stressors of living in a world that requires constant vigilance to avoid getting the virus can escalate depression and anxiety.

According to an April 1, 2002, article in Lancet, the impact of the coronavirus pandemic may hit those who struggle with mental health issues more intensely:

  • Mental disorders increase the risk of infection, including pneumonia.
  • People with mental health disorders may face even more barriers in accessing timely health services.
  • Since the pandemic has caused a “parallel epidemic in fear, anxiety, and depression,” people already depressed may experience more intense symptoms, and more people may develop clinical depression.

Nourishing beneficial bacteria that can strengthen your immunity and decrease depression risk is therefore even more critical. For more information about COVID-19 and your immune system, check out the Prebiotin blog, Coronavirus and the Importance of a Strong Immune System. 

 (All of our blogs are carefully researched, contributed to, and reviewed by our senior management and support team.)


Organizations that Educate and Offer Help

  • National Alliance on Mental Illness 1-800-950-NAMI (1-800-950-6264). NAMI is the largest grassroots organization devoted to improving the lives of those affected by mental illness. Through various programs, it aims to change public perception about mental illness, help its members manage mental illness, and build up family relationships.
  • Anxiety and Depression Association of America1-240-485-1001. The ADAA works to improve the quality of life of those affected by anxiety and depression related disorders. The programs of the nonprofit provide education, resources, and support for people to find treatment.
  • National Institute of Mental Health 1-866-615-6464. The NIMH is the largest research organization in the world committed to understanding the treatment and prevention of mental disorders. It funds research “to transform the understanding and treatment of mental illnesses through basic and clinical research, paving the way for prevention, recovery, and cure.”
  • Centers for Disease Control and Prevention Division of Mental Health 1-800-CDC-INFO (1-800-232-4636). The mental health arm of the CDC is a good source of public health information on mental health.

Resources for Women

Resources for Veterans


Finding Treatment:

Deployment Health Clinical Center:

U.S. Department of Veterans Affairs Mental Health Resources:

The U.S. Department of Veterans Affairs mental health resources provides information about mental health and support services specifically for veterans, such as the following programs:

  • The VA Mental Health connects veterans and their families to mental health services. The programs aim to enable people with mental health problems to live meaningful lives in their communities and achieve their full potential.
  • Vet Centers Community-based centers that provide a range of counseling, outreach, and referral services to eligible veterans in order to help them make a satisfying post-war readjustment to civilian life.
  • National Call Center for Homeless Veterans is a hotline intended to assist homeless veterans or veterans at-risk for homelessness and give them access to trained counselors 24/7.
  • Make the Connection is VA’s public awareness and outreach campaign. The goal of the campaign is to raise awareness on mental health symptoms, conditions, and treatment.

Online Screening Tools:

  • Free, confidential, online screenings for anxiety, depression, mood disorders, PTSD and other conditions are available at, Mental Health America’s screening service.

National Center for Post-Traumatic Stress Disorder:

  • The Department of Veteran Affairs website offers a broad range of information about post-traumatic stress disorder and treatment options as well as a VA facilities locator. You may also call (802) 296-6300.

National Resource Directory:

  • The National Resource Directory, or NRD connects wounded warriors, injured and ill service members, veterans, and their families with national, state, and local support programs. The NRD is a partnership among the Departments of Defense, Labor, and Veterans Affairs.

Moving Forward:

  • Moving Forward is a free, on-line educational and life coaching program that teaches problem-solving skills to help you to better handle life’s challenges. It is designed to be especially helpful for veterans, service members, and their families.