“Our brain talks to our gut, and the microbiome (organisms that live in our gut) talk to our brain,” says Mahmoud Ghannoum, PhD, a professor in the department of pathology and a faculty member of the digestive health research institute at Case Western Reserve University School of Medicine in Cleveland. Researchers like Dr. Ghannoum are looking into how the gut microbiome and the mind communicate, as well as how the microbiome influences depression, a condition that affects more than 17 million adults in the United States. “Although research on the microbiome and mental health is becoming increasingly popular, little is still known about the exact mechanisms or ways that the gut microbiome regulates brain and behavior,” says Nicole Rodriguez, a clinical scientist at the University of Alberta in Edmonton. Rodriguez has conducted research related to the gut microbiome. Scientists who are studying this relationship hope to discover new treatments for depression, according to a review published in August 2021 in Frontiers in Nutrition, which Ghannoum coauthored. Why is there a need for new treatments? While one of today’s standard treatments for depression, antidepressant medication, is effective for many patients, it does not work for everyone. And even when medications do help, they often have side effects like weight gain and sexual dysfunction that cause some people to stop taking them. An article published in August 2019 in Physiological Reviews found that the composition of gut microbiota altered mood in small studies conducted on mostly healthy adults, as well as adults with gastrointestinal conditions like irritable bowel syndrome (IBS). Research is ongoing, but it seems at least some people with depression “tend to have a change or an imbalance in the microbiome where we have reduction or decrease in beneficial organisms, an increase in pathogenic ones, the ones that cause disease,” Ghannoum explains. For instance, a review published in May 2022 in Physiological Medicine found that people with certain mental health conditions — MDD, bipolar disorder, or schizophrenia-spectrum disorders — had higher levels of the microorganisms Streptococcus, Lactobacillus, and Eggerthella, but lower levels of Faecalibacterium in the gut — and that these variations were associated with more severe mental health symptoms. Factors that may contribute to these differences in gut composition include medication use, diet, alcohol use, or smoking, the researchers noted. What’s more, diet does not seem to be the only factor affecting gut microbiota. New data published in February 2022 in Nature Genetics suggests that higher levels of the bacteria Morganella in the gut significantly increases a person’s odds of developing MDD and may even cause the condition. As their understanding of the complex relationship between the gut microbiome and mental health unfolds, scientists hope to confirm such findings in large-scale studies, as well as pinpoint how the gut microbiome influences depression. They also want to know if certain medications and dietary changes can alter the gut microbiome in ways that reduce the risk of depression and other mental health conditions. RELATED: 5 Surprising Symptoms of an Unhealthy Gut
3 Ways to Boost Gut Health (and Mood, Too)
One thing that’s already clear: You don’t have to wait to take steps to improve your gut health in general and likely improve your mood, too. The aforementioned Frontiers in Nutrition review points to certain lifestyle modifications that promote microbiome health and ease depressive symptoms. As long as your doctor okays them, consider adopting some, or all, of these lifestyle strategies.
1. Eat Less Refined Sugar and More Plant Foods
Diets high in refined sugar and other added sugars negatively impact microbes in your gut, according to a review published July 2019 in Nutrients. An earlier article, published in 2017 in Scientific Reports, found a link between sugar intake and symptoms of depression. Foods to focus on, Ghannoum says, include “good proteins from plants, healthy oil such as coconut oil or extra-virgin olive oil, and fruits and vegetables.” More specifically, an anti-inflammatory diet (one full of fruits, vegetables, whole grains, and healthy fats, and with fewer animal products, processed packaged foods, and other foods associated with inflammation in the body) can help reduce depressive symptoms, according to a meta-analysis published in Molecular Psychiatry in July 2019.
2. Add Aerobic Exercise to Your Daily Routine
It doesn’t matter whether you walk, run, cycle, or engage in another aerobic activity: Regular endurance exercise enhances gut health. “There is a beneficial association of exercising with the microbiome,” Ghannoum confirms. “It will increase the diversity, which means you have a lot of different microorganisms there.” A diverse microbiome is good for your health, whereas a less diverse microbiome is linked to digestive health issues, per research published in March 2016 in Frontiers in Microbiology. How much exercise is enough to reap that benefit? A study published in June 2021 in Frontiers in Nutrition suggests that moderate-intensity endurance exercise is best for promoting a healthy gut microbiome. “Exercising 30 minutes a day, even walking, will be very good,” says Ghannoum. In fact, regular exercise could deliver a better mood right away. One small study published in March 2022 in Psychology of Sport and Exercise found that it takes only 30 minutes of moderate exercise to improve depressive symptoms for an additional 75 minutes after exercising. RELATED: 7 Great Exercises to Ease Depression
3. Fuel Your Microbiome With Probiotics and Fiber
You can easily add probiotics (the live “good” bacteria that flourish in your gut) and fiber — a type of carbohydrate that feeds the good bacteria — to your diet by eating certain foods or taking supplements. According to a review published in October 2021 in Molecules, probiotics affect the composition of microorganisms in the gut, which in turn may lower the risk of mood disorders, among other potential health benefits. That said, it’s not yet clear whether probiotics can help treat an existing mood disorder, so more research is needed before they can be recommended specifically to manage depressive symptoms. What’s more, “how these supplements interact with concurrent antidepressant medications and whether these supplements can be used as preventive measures [against depression] is still largely unknown,” Rodriguez says. If you take antidepressants or other medications, be sure to talk to your doctor before trying a probiotic supplement, to avoid potential drug interactions. As for fiber, a diet high in this nutrient may lessen the severity of symptoms of depression, per a review published in May 2020 in Nutrition Reviews. Current dietary recommendations advise adults to consume 14 grams of fiber for every 1,000 calories of food you eat each day. Top fiber-rich foods, Mayo Clinic experts say, include:
LentilsBlack beansGreen peasRaspberriesWhole-wheat spaghettiPearsBran flakesBroccoliOatmealApple, with skinBrussels sprouts
