“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, M.D., 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.”
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 “snap out of it,” join a gym, take a class, eat more greens, or just get over it; the suggestions are often 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 16.2 million adults in the United States.
About 6.7 % of American adults have had at least one major depressive episode in a given year. Worldwide, about 300 million people suffer from depression, according to the World Health Organization (WHO). It’s the world’s leading cause of disability.
Depression and cognitive decline: a public health crisis
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. 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 may become a public health crisis as soon as 2020.
When bare survival is impossible
With a 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 2% of those people ever treated for depression in an outpatient setting will die by suicide; this increases to 4% for those ever treated for depression in an inpatient hospital setting.
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
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 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 Smithsonian.com.
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).
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 more 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.
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, in the 12-week “SMILES” trial, 33 individuals received diet interventions; 25 other individuals received just social support.
The researchers found diet can help reduce the symptoms of depression: “These results indicate that dietary improvement may provide an efficacious and accessible treatment strategy for the management of this highly preventable mental disorder, the benefits of which could extend to the management of common co-morbidities.”
What about the prescription drugs I take?
The drugs we take can also have a major impact on changes in the microbiome that can lead to depression. Many studies have shown the long-term negative impact of even one course of antibiotics on the beneficial bacteria in the gut microbiome. 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.
Mark Olfson and his collaborators at Columbia University found the drugs individuals take can have a stunning impact on the gut microbiome. The researchers examined results from the National Health and Nutrition Examination Survey, where 26,192 adults listed the medications they were taking at the time of the survey and completed a depression screening test.
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.
According to a JAMA study, the drugs we take also can have a major impact on changes in the microbiome that can lead to depression. Researchers found that one in three Americans are taking drugs that can lead to depression.
Many people take multiple medicines like these. Study researchers found that people who take these medicines are, in fact, more likely to be depressed. In an NPR interview, Olfson notes he was surprised by the “strength of the association between the number of medications and the likelihood of being depressed.”
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 three times a week. The group started with 30 minutes of easy walking or cycling and increased to an hour of vigorous jogging or pedaling.
Blood and fecal samples were tested before and after the six-week period. The volunteers were asked to not change their diets.
The results? Definite changes in the microbes that populate the gut microbiome, with a widespread increase in bacteria that produce the short-chain fatty acids (SCFA), especially butyrate. SCFA are associated with reduced disease risk and improvements in brain health.
Those who were leanest had the greatest gut improvements. Without exercise, the gut microbiome returned to the pre-study condition.
In a January 2019 study in JAMA, researchers at Massachusetts General Hospital are even more definite that higher levels of physical activity may reduce risk 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
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
- Jerusalem artichoke
- Leeks and onions
- Oatmeal, flax, and barley
- Cruciferous vegetables, such as broccoli, Brussel sprouts, kale, and cauliflower
- Fruits like apples, bananas, raspberries, and blueberries
Foods with live probiotic bacteria are also beneficial. Good choices include:
- Fermented vegetables like kimchi or sauerkraut
- Fermented soybeans (miso)
- Kombucha tea
- Plain yogurt
That food impacts our mental health was confirmed in 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.” The team concluded, “Dietary interventions hold promise as a novel intervention for reducing symptoms of depression across the population.”
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, in their daily diet. For example, even two pieces of whole grain bread and a banana for breakfast only contain 2 to 3 grams of fiber.
Since it’s sometimes difficult to eat enough foods rich in fiber, 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.
OEI: fermented on both sides of the colon
These two chicory-based fiber products (oligofructose-enriched inulin or OEI) also have a notable therapeutic impact. The right side of the colon, where fuel from the small bowel enters the colon, is the site of enormous bacterial activity. Because of its small structure molecule, oligofructose gets fermented very quickly in the right colon and nourishes bacteria just in this part of the colon.
This full spectrum effect makes Prebiotin’s proprietary chicory-based product especially effective, because it is fully fermented in the colon and nurtures beneficial bacteria like bifidobacteria and lactobacilli in both sides of the colon.
As these highly desirable bacteria flourish, they generate more of beneficial short chain fatty acids (SCFAs)—such as butyrate, propionate, and acetate. 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
While the link between gut health and our brain is still being explored, the research is clear—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, eating fiber-rich foods, and adding a medically-researched prebiotic fiber like Prebiotin that can help friendly bacteria flourish.
The importance of nourishing the right bacteria in our “second brain” to address depression and other mental health conditions is summed up succinctly in a 2015 article in 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! References Crisis: Finding Treatment: 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:
* Gabriele is a science writer with over 25 years of experience writing on health and science topics. As writer/editor for Prebiotin, she supports website and marketing efforts.
(All of our blogs are carefully researched, contributed to and reviewed by our senior management and support team.)
Organizations that Educate and Offer Help
Resources for Women & Depression
Resources for Veterans
Deployment Health Clinical Center:
U.S. Department of Veterans Affairs mental health resources:
Online screening tools:
National Center for Post-Traumatic Stress Disorder:
National Resource Directory:
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!
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: