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No matter how fit you are, and no matter how good you look on the outside, underneath it all, one thing that matters most is your body’s (good) bacteria balance. Of the estimated 100 trillion cells in the body, only about 10 percent are human. The rest are bacteria — up to 5 pounds worth, and most of them are in your gastrointestinal tract. According to emerging research, those gut bacteria can have a profound impact on your mood and overall mental well-being, says one 2017 literature review published in the journal Clinics and Practice.
Sometimes called the “second brain” or the “gut brain,” the digestive tract is the body’s only organ to house its own nervous system. The enteric nervous system is a neural network that consists of 500 million neurons, five times the amount in the spinal column. It operates independently from the central nervous system and continues to function even when the vagus nerve — the main channel of communication between the gut and the brain — is severed.
This article is part of our ongoing series Eat Clean For Mental Health. You can find that here.
How Gut Microbes Impact Your Mood
Because of the many similarities in the immune system and nervous system, researchers initially believed gut microbes influenced mood through the immune system, more or less by using immune cells to send signals to the brain. But newer research has found that there’s a direct line from your gut to your brain — called the gut-brain axis.
Hormones, neurotransmitters, and other compounds released in the gut can send signals to your brain. For example, your gut is responsible for making about 95 percent of your serotonin, the feel-good compound that boosts your mood. Your brain can communicate with your gut, too, because the gut-brain axis is what’s called bidirectional. Put simply, it’s a two-way street.
This growing body of new and compelling research has found that the makeup of your gut microbiota can have a profound impact on your brain and mental health.
Here are a few notable examples:
- An unhealthy makeup of gut microbiota — called dysbiotic — may allow more compounds that are harmful to leak through the walls of the GI tract and hamper brain function and mood.
- An inflamed GI tract increases the “leakiness” of your gut, which means potentially harmful molecules can get into your bloodstream and cross the blood-brain barrier, hindering your brain health (memory, anxiety, and depression).
- The microbiome in people with a particular makeup of bacteria is more likely to lead to more inflammation and, thus, a higher likelihood of mental health conditions.
- An increase in inflammation-causing compounds can up your risk of developing depression and/or anxiety.
Why You Want To Have A Healthy Gut Microbiome
When you have a “healthy gut” the good bacteria create a protective-like lining in your intestines which allows healthy digested nutrients (think: carbs, protein, vitamins, minerals, etc.) to cross through the intestinal wall and into the body. That healthy lining also prevents many outside compounds from crossing and getting into the body and causing harm. When the lining of your GI tract is not-so-healthy, there are gaps or holes that allow compounds that can cause illness into your body — hence the term “leaky gut”. Once they’ve crossed the intestinal wall, these compounds act as irritants to trigger low-grade inflammation fueling disease, which includes depression and anxiety.
Knowing now that your gut microbiome and what you eat are so closely connected, what can you do to improve your gut microbiome — and in turn boost your mood? Here are 5 ways to improve your gut microbiome.
5 Diet Changes to Improve Your Microbiome
1. Consider a high-quality probiotic supplement
Research suggests that probiotic supplements may specifically help with depression, per a 2020 meta-analysis review. Other preliminary studies show probiotics can suppress pro-inflammatory compounds like cytokines and also strengthen the GI tract lining to prevent harmful compounds from crossing in humans. Then, in animal studies, probiotic supplements have been found to blunt stress hormones and help regulate a part of the brain that when unregulated spurs mental illness.
So what kind of probiotic supplement should you seek out? “Research suggests you need to know what strains your individual gut needs—and that’s almost impossible to know,” says Carolyn Williams, PhD, RD, co-host of the Happy Eating Podcast, and author of the cookbook Meals That Heal. “Still, there does seem to be some benefit from taking a probiotic supplement. I recommend taking a multi-strain probiotic — one that has 8 or more strains — and has one or more of the Bifido bacteria genus and one or more from the Lactobacillus genus.” Here are 4 other probiotic supplement tips from Williams:
- Choose one with 1 to 10 billion CFU—that’s how many live microorganisms are in a dose.
- Make sure it contains (and is labeled as having) live and active cultures.
- Look for a brand with approval from a 3rd-party organization as probiotic supplements aren’t FDA regulated in the same way that prescription drugs are.
- Check the expiration date.
2. Feed your gut with prebiotics.
Prebiotics are the nutrients in foods that literally feed the good bugs (aka probiotics) in your gut microbiome. They are technically indigestible fibers. In one study, people who took a daily prebiotic supplement for three weeks were better able to deal with anxiety and depression than a placebo group.
That said, it’s easy to add prebiotics to your diet through food. Foods rich in prebiotics are plant foods and they are concentrated in bananas (particularly slightly green, or under-ripe, ones), berries, artichokes, asparagus, beans, onions, garlic, leeks, and whole grains, per the Academy of Nutrition and Dietetics.
With prebiotics, too much of a good thing is a reality: consume too much and upset bowels (e.g., gas and diarrhea) are likely.
3. Include fermented foods in your diet.
In addition to taking a probiotic supplement, include fermented foods in your diet. Not only have naturally fermented foods been used for thousands of years, they often contain a variety of good-for-you bacteria. “People often forget to take care of their good bacteria,” says Williams. So, in addition to eating foods high in fiber from plant sources, fermented foods are key. “One study looked at a period of 6 to 8 weeks and found that eating fermented foods really had the most impact on the overall gut bacteria composition compared to eating high fiber foods,” says Williams.
Yogurt, kefir, kimchi, miso, kombucha, and sauerkraut (refrigerated, not canned) are some of the most common and easy-to-find fermented foods. Remember, though, that probiotics are easily killed with heat, so eat these items raw, not cooked for the biggest benefit. Try this Miso, Almond & Mushroom Soba Noodle Bowls recipe for a healthy helping of fermented foods.
4. Reduce or eliminate foods that harm beneficial gut bacteria.
Anything that’s not natural to the body — think artificial ingredients or additives — or items consumed in excess have the potential to disrupt that balance of good bacteria. “So, minimize added sugars, saturated fats, and trans fat. Be mindful of excessive alcohol, protein, and processed foods,” advises Williams. The keyword here is to minimize, not necessarily eliminate.
5. Aim for an anti-inflammatory diet overall.
Making anti-inflammatory edits to your diet can have a significant impact on your gut microbiome in as little as 24 hours, per a review study in the journal Clinics and Practice. “Slowly move towards a minimally-processed diet,” says Williams. “That doesn’t mean you have to eat a diet made fully from scratch, but do pay attention to the ingredients that are in the foods you’re eating.”
An anti-inflammatory diet is rich in seafood that’s chock full of omega-3 fatty acids — or cold-water seafood such as salmon, tuna, oysters, mussels, sardines, etc. Leafy greens and berries are daily staples in an anti-inflammatory diet. And then foods like orange veggies for their beta-carotene and olive oil for its antioxidants are crucial.
Overall, these tips, plus the 4 leading up to this final piece of advice all support what you need to do to follow an anti-inflammatory diet.