Your gut can affect your mood

For many years, mental health has been viewed as something that begins and ends in the brain. But an expanding field of research is revealing a key player in the story of our emotions: the gut. The trillions of bacteria that live in our digestive tract don’t just help digest food. They seem to communicate directly with the brain, affecting everything from the ability to tolerate stress to symptoms of depression and anxiety. Scientists call this dual relationship the gut-brain axis, and it’s rapidly reshaping the way we think about mood and mental health.

This connection is not just theoretical. Studies have found that people with depression often suffer from it Less microbial diversityThat probiotics It may relieve symptoms Of anxiety, and that dietary transformations It can change brain chemistry associated with mood Within days. “There is now more scientific evidence than ever that there is a direct link between gut health and brain health,” says Dr. Karl Kwok, a gastroenterologist at Kaiser Permanente in Southern California. “The gut microbiome or other gut bacteria can absolutely impact neuronal function.”

The question scientists are now racing to answer is how far this effect goes, and how we can harness it to feel better, from the inside out.

If you’ve ever had butterflies in your stomach before a big presentation, you’ve felt the gut-brain connection in action. For decades, scientists assumed that the gut simply followed the brain’s lead. but research It is now suggested that the trillions of microbes in our gut may play a surprisingly active role in shaping our emotions and mental health.

“The lines of communication between the gut microbiome and the brain appear to involve products of gut bacteria, including neurotransmitters,” says Dr. Roy Zigelstein, a cardiologist and researcher in depression and cardiovascular disease at Johns Hopkins University. “In addition, changes in lipids or lipids in the blood and changes in chemicals that cause inflammation may be related to the gut microbiome and ‘talking’ to the brain.”

These biochemical “conversations” travel through multiple channels—the nervous system, the hormones, and the immune system—to form the gut-brain axis.

Dr. Katherine Njo, a gastroenterologist and movement director at the Hoag Institute for Digestive Health in California, likens it to a crowded city. “Imagine your gut is a crowded city, and your mind is City Hall up the hill,” she says. “The two must stay in constant contact to keep everything running smoothly.”

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This communication occurs through several main pathways. The vagus nerve acts as a direct line between the intestines and the brain. The immune pathway relays messages when inflammation is high or low. The endocrine system broadcasts “updates” about hunger, stress and mood.

“Microbes help decide which programs to broadcast, a relaxed channel when things are balanced, or a tense broadcaster when they aren’t,” Ngo says.

Research supports this idea. one He studies Describes how bacterial metabolites, neurotransmitters such as serotonin and GABA, and inflammatory molecules move from the gut to the brain, affecting mood, cognition, and the body’s response to stress.

In fact, about 90% of the body’s serotonin — the neurotransmitter often called the “happy chemical” —It takes place in the gastrointestinal tractNot the brain. “It is not surprising that one of the most common classes of medications for treating mood disorders, SSRIs, has gastrointestinal side effects,” Ngo says. “They operate on a deeply interconnected system.”

For years, researchers have suspected that disturbances in the microbiome may contribute to anxiety, depression, and even trauma-related disorders. On a large scale Reviews It has been found that people with depression often have lower microbial diversity and higher levels of pro-inflammatory species.

“Most of the evidence so far links the gut microbiome to depression and anxiety,” says Zigelstein. “However, other conditions have also been examined, including bipolar disorder, schizophrenia, autism spectrum disorder, ADHD, post-traumatic stress disorder, anorexia, and obsessive-compulsive disorder.”

Animal studies provide some of the most interesting evidence. “Germ-free mice — those raised without gut microbes — show more anxiety and hyperactivity than normal mice,” Njoo says. “When researchers transplant gut bacteria from depressed people into these animals, they begin to exhibit depression-like behaviors.” This finding, confirmed by multiple studies, reinforces the idea that gut imbalance may play a role in regulating mood.

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However, human data is more accurate. “While the evidence that the gut microbiome affects mood is relatively strong, the evidence that changing the gut microbiome improves mood is not as strong,” warns Zigelstein. This is largely due to small sample sizes and differences in study methods and probiotic formulations.

2021 review in Advances in nutrition He concluded that although the gut-brain axis is a promising target for improving mental health, more rigorous trials are needed to confirm whether interventions — such as probiotics, diet, or prebiotics — can reliably prevent or treat mental health disorders.

But the early signs are encouraging. “Modern analysis “Researchers from the University of Oxford reviewed randomized controlled trials in which some participants received interventions to change the gut microbiome,” says Zigelstein. “They found that probiotics reduced symptoms of depression and anxiety.” But even the study authors acknowledged that this is not the final word, and that more research is needed.

As science develops, one fact is already clear: lifestyle habits have a significant impact on the conversation between the gut and the brain. What you eat, how you deal with stress, and how much you sleep are all factors that can change the microscopic balance inside your gut, and perhaps your mood.

“The foods you eat feed your gut microbes, shaping their composition and the metabolites they produce,” Ngo says. “Diet is one of the biggest factors influencing the gut microbiome.”

Zigelstein agrees, noting, “Dietary changes seem to have the biggest impact. A healthy gut microbiome is promoted by foods that don’t raise blood sugar much, and by foods rich in omega-3 fatty acids — such as fish, chia seeds, flaxseeds, and walnuts.” He adds that this type of diet “is likely to have many other health benefits apart from any potential impact on the gut microbiome or mood.”

“Whole grains, fruits, and cruciferous vegetables like kale are helpful in amplifying healthy gut bacteria, which in turn can improve brain health and mood,” says Kwok. “But more than half of the average American diet is based on ultra-processed foods, which can weaken the mucous lining of the digestive tract over time and damage the brain.”

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US Centers for Disease Control and Prevention (CDC) Reports 57% of calories in the average American diet come from ultra-processed foods, which can contribute to chronic inflammation and reduced microbial diversity, which are major risk factors for mood disorders.

The gut microbiome has been shown to be very responsive as well. “It can change over days or even hours in response to diet, stress or medication,” Ngo says. “But the effect on mood is a little more complex and slower.” She adds that rapid changes, such as eating a meal high in fat or sugar, can change the microbial composition within 24 to 48 hours, although emotional effects often take days or weeks to appear.

Other lifestyle factors are also important. Chronic stress and lack of sleep can reduce beneficial bacteria and increase inflammation, while regular exercise helps restore balance. “It’s a symphony of activities working together to improve mood-related gut bacteria,” says Kwok.

With so much hype around the microbiome, it’s easy to view it as the next frontier in mental health care. But experts warn against considering it a magic bullet.

“The connection between your gut and your brain is real, and eating well, managing stress, and supporting your gut can help improve your mood,” Ngo says. “But these strategies are not a cure for depression or anxiety.” For most people, gut-focused approaches should be a complement to — not a replacement for — proven treatments such as therapy or medications.

However, the gut-brain axis opens new doors. In 2024 review in Frontiers in pharmacology Scientists have found that probiotics may reduce inflammation and pathogenic microbes in the gut, as well as potentially improve cognitive outcomes. “There is evidence that altering the gut microbiome via probiotics, prebiotics, dietary changes, or even fecal microbial transplantation can improve mental health,” Ziegelstein says. “The evidence seems strongest for probiotics on depressive symptoms, although individual studies are too small to be certain.”