The Body’s Second Brain: How Your Gut Could Be Affecting Your Mood
By Alicia Armeli

SecondBrainWhen was the last time you trusted your gut? Or just had that gut feeling about someone? Perhaps had butterflies in your stomach? Even before we had scientific proof of a link existing between the brain and gut, we had common sayings like these to express this phenomenon. With stressful situations becoming an accepted part of everyday life, we often don’t stop to ask: Could what’s happening in my gut be responsible for my mood?

The Brain-Gut Axis

The brain is responsible for communicating with every part of the body through an intricate network of neurons and nerve fibers. But when it comes to the gut, it’s a two-way street.

Comprised of 100 million neurons,1 hormone-secreting cells, and neurotransmitter-releasing microbes, the gut is often referred to as the body’s second brain. “It has its own sensory system so it can detect what’s going on within the gut. It has a motor system to control how it functions and it has an integrative system to understand these signals and decide the most important thing to do,” explains Dr. Lisa Goehler PhD, Research Faculty at the University of Virginia School of Nursing. “This enables the gut to act independently of the brain.”

The gut is responsible for relaying primal messages to the brain such as pain signals as well as hunger and satiety cues, but it takes it a step further. Signals from the gut can communicate emotions as well. “The places where emotions are processed in the brain are the same places that process signals from the body, especially from the gut,” says Dr. Goehler.

Mood and the Gut

This bidirectional communication is crucial for digestion and mood balance but can be disrupted when the body is chronically stressed. When this occurs, the body can respond in ways such as anxiety and depression.2,3 According to the Anxiety and Depression Association of America, nearly 40 million adults in the US are affected with anxiety and it’s common for those with anxiety to also experience depression.4

“When experiencing stress, especially chronic stress, the body knows something isn’t right. Reactions to stress can be anxiety or depression. The body responds by elevating stress hormones—like cortisol,” Dr. Goehler explains. “Cortisol has negative effects on gut tissues, especially the gut barrier, because it can downregulate the proteins that control gut barrier permeability—this can lead to ‘leaky gut.'”

Although still in its infancy, research regarding leaky gut may point to a problem in the small intestine where the majority of nutrients are absorbed through tiny openings in its lining. A healthy small intestine prides itself on having the “Goldilocks” of semi-permeability—it absorbs into the bloodstream what’s needed, like nutrients, while simultaneously blocking what’s not, like large undigested food particles. This results in a systemic “just-right” balance.

In leaky gut, the small intestine loses its semi-permeability thereby transferring unwanted particles into circulation. Particles passing through the gut lining can resemble the body’s own natural antigens and initiate a heightened immune reaction that can result in tissue damage.5 For this reason, some studies have linked leaky gut with conditions such as autoimmune diseases, joint pain, and digestive illnesses.6

New research may even connect leaky gut to mood disorders like depression. When intestinal lining loses its integrity, gut bacteria products like lipopolysaccaharides can enter into the bloodstream. In depression, heightened immune responses targeting bacterial lipopolysaccharides have been seen. This may be an important piece of the puzzle because certain bacterial products are capable of entering circulation and can have harmful effects on the nervous system.7 It’s important to remember, however, that correlation doesn’t imply causation. More studies are needed to confirm the existence of leaky gut as well as a direct link between this condition and mood disorders.

How brain and gut health are intertwined isn’t as simple as the proverbial chicken or egg question—which disorder, mood or gut, happened first and set the other into motion is still unclear. “It can go both ways,” says Dr. Goehler. “You can start out with general anxiety that causes inflammation in your gut that can then drive more anxiety. Or you can start with a ‘bottom-up stress’ like leaky gut that can cause dysbiosis [gut bacterial imbalance] and lead to unexplained anxiety.” Because of this, therapeutic options must involve care for both the gut and the mind.

Healing the Gut

Ensuring gut bacteria are healthy is a wise place to start. Gut bacteria not only have the ability to regulate gut permeability8 but also can activate the vagus nerve9—which could possibly be key in treatment. The vagus nerve serves as a channel between the brain and gut and studies show activating this pathway can reduce both inflammation and depression.10 Eating probiotic-rich foods like yogurt, miso, tempeh, sauerkraut, kimchi, and kefir can help boost levels of good bacteria, decrease inflammation and get the gut lining back on track.

Another type of available treatment is glutamine, or L-glutamine. Glutamine is a type of amino acid with antioxidant properties that serves as the preferred fuel source for cells lining the intestinal wall. In supplement form, it has been shown to increase gut barrier integrity and function11 and because of this, may start to heal the gut lining.

Processed fried foods high in sugar and fat may play a role in producing elevated immune responses and inflammation in the gut.11 Switching them out for nutrient-rich anti-inflammatory foods such as coldwater fish rich in omega 3’s may help to keep systemic inflammation at bay. Research has shed light on particular phytonutrients such as quercetin—an antioxidant seen to boost gut integrity.8 Quercetin can be found in numerous fruits and vegetables like apples, berries and leafy greens. Spices like curcumin have been found to reduce gut inflammation.11 Trace minerals such as zinc may help maintain gut integrity8 and can be found in foods like seafood, seeds, and poultry.

Healing the Mind

Referring to stress in the mind as “top-down stress,” Dr. Goehler says eating a good diet is helpful but it can’t be the only form of treatment. “It’s important to treat the mind, too. Life is always going to have stress. If you don’t face it, it’s not going to go away and can lead to other chronic diseases.”

As mentioned, activating the vagus nerve can help. “Activating the vagus nerve rebalances things,” says Dr. Goehler—simply by doing something we do every day. What is she talking about? Breathing.

Particularly breathing deeply and slowly. According to Evidence-Based Complementary and Alternative Medicine, slowing breathing to about 5-6 breaths per minute triggers stretch receptors in the lungs that feed to the vagus nerve. This has been found to improve oxygen saturation, lower blood pressure, and reduce anxiety.12

Other techniques that encourage mind-body awareness are yoga and meditation. Often referred to as Mindfulness-Based Stress Reduction (MBSR) techniques, both yoga and meditation may incorporate deep breathing while also teaching individuals to observe situations and thoughts in a calm and accepting manner.  MBSR techniques have been shown to reduce stress, depression, and anxiety.13

Listen to Your Gut

“Really, it’s all about balance,” Dr. Goehler advises. “The body needs to be in a state where every tissue can do its job. The problem with chronic stress is sometimes it’s hard to just turn it off unless we start to focus on the things we can do consciously to release tension.” To regain whole mind-body balance, work with your physician and a registered dietitian to create an individualized treatment plan that works with your body’s natural healing process.

ABOUT THE AUTHOR   Alicia Armeli has a Master of Science in Nutrition and Whole Foods Dietetics (MSN/DPD) and is a registered dietitian nutritionist, a certified dietitian, and a holistic life coach. In addition to writing, she enjoys singing, traveling abroad and volunteering with her local animal shelter.


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