No matter how fit you are, and no matter how beautiful, tan, perfectly coiffed, or finely muscled, underneath it all, what matters most is your body's balance of good bacteria. 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 in the gut. And according to emerging research, they can have a profound impact on mood, behavior, and well-being.
Sometimes called the "second brain" or the "gut brain," the digestive tract is the body's only organ to house its own nervous system. Called the enteric nervous system, this neural network 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.
Gut Microbes Impact Mood
Because of many similarities in the immune system and nervous system, researchers initially believed gut microbes influenced mood and behavior through the immune system, more or less by using immune cells to send signals to the brain. But new studies suggest gut microbes impact mood and behavior by directly interacting with the nervous system, without involving the immune system. There may be a complex neurochemical delivery system in which microbes such as probiotics can send messages directly to the brain. And it's also known that gut bacteria produce neurochemicals that impact learning, memory, and mood; for example, the gut is responsible for making about 95 percent of the body's serotonin, which influences mood, appetite, and sleep.
Dozens of new and compelling studies have found that the makeup of bacteria in the gut has a profound impact on brain chemistry, behavior, learning, and mood. For example:
- The microbiome in patients with major depressive disorder is significantly different from that of people who don't suffer depression.
- A lower amount of certain bacteria (for example, Faecalibacterium) is associated with more severe depression.
- Taking probiotics can lessen anxiety and improve feelings of well-being.
- MRI (magnetic resonance imaging) findings show changes in regions of the brain crucial in emotional processing after taking probiotics.
- Specific probiotics (beneficial bacteria) can significantly decrease anxiety-like behavior in rats and reduce psychological distress in humans.
- Altering gut flora has been shown to decrease stress response and improve overall feelings of well-being.
- Higher levels of Lactobacillus rhamnosus bacteria in the gut can increase the number of GABA (gamma-aminobutyric acid) receptors. GABA is a neurotransmitter that curbs anxiety.
- Bifidobacterium longum helps ease anxiety and depression in people who suffer from GI disorders such as Crohn's disease, ulcerative colitis, and irritable bowel syndrome (IBS).
Fecal Microbiota Transplantation
In light of these findings, researchers are experimenting with fecal microbiota transplantation (FMT), in which microbiota from a healthy person are inserted into a sick person's gut. This process has been shown to effectively treat C. difficile, an antibiotic-resistant pathogen that can be fatal. And it may be effective as a treatment for diabetes and obesity. In animal studies, obese mice that received transplants from lean mice lost weight; in human studies, when microbiota from lean donors were transferred to the guts of patients with metabolic syndrome, the researchers found striking improvements in the recipients' sensitivity to insulin. The next frontier of research: FMT for treating depression, anxiety, and mood disorders.
But the practical use of fecal transplants for mental health is many years away. In the meantime, you can heal your gut, ease anxiety, and lessen depression with simple, effective cures. Try these, and get your gut feelings in order:
9 Ways to Improve Your Microbiome
1 - Reduce or eliminate foods that harm beneficial gut bacteria and consequently impact mood and behavior.
These include sugar, corn syrup, and processed foods. Certain medications, especially antibiotics, NSAIDs, steroids, and proton-pump inhibitors, also upset the microbiome
2 - Heal your gut.
Poor diet and lifestyle can lead to a condition called "leaky gut," or intestinal permeability, which has been implicated in many diseases, including depression. Many natural herbs and supplements promote healing of the intestine's mucosal lining. Some of the best include L-glutamine, an amino acid that can heal soft tissue like the lining of the intestines; quercetin, which helps reduce permeability; N-acetylglucosamine (NAG), a monosaccharide that can improve intestinal permeability, especially in conjunction with MSM; zinc, which can tighten the junctures characteristic of leaky gut; and deglycyrrhizinated licorice (DGL) root, a form of licorice that's free from glycyrrhiza-the compound that can raise blood pressure-which helps maintain the mucosal lining of the stomach and duodenum.
3 - Take a good probiotic supplement.
New research suggests probiotics can ease anxiety, and may even be a powerful treatment for autism. In one study, mice with features of autism had lower levels of certain probiotics than did normal mice; when they were given the strains of probiotics they were lacking, symptoms were reversed. In another study, volunteers who took probiotic supplements for a four-week period had improved mood and fewer ruminating thoughts. Choose a broad-spectrum supplement, and be sure it includes Lactobacillus acidophilus and Bifidobacterium lactis (B. animalis).
4 - Include fermented food in your diet.
In addition to taking a probiotic, include fermented food in your diet. Naturally fermented foods have been used for thousands of years, and contain a wide range of bacteria so you'll cover all your bases. Yogurt, sauerkraut, kefir, kimchi, miso, and kombucha are some of the most common and easily accessible fermented foods. You'll also find fermented cod-liver oil, green foods, and protein powders-great ways to add probiotics to your morning smoothies.
5 - Feed your gut with prebiotics.
Prebiotics, indigestible foods that provide "food" for beneficial microorganisms in the intestines, can improve the microbiome and enhance mood. 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. The best prebiotic foods include Jerusalem artichokes, asparagus, onions, garlic, jicama, and radishes. Prebiotic supplements include inulin, chicory root, arabinogalactan polysaccharides and FOS (fructooligosaccharides). A number of these are high FODMAP and can cause tummy upset. Casa de Sante probiotic and prebiotic combo for IBS & SIBO is low FODMAP certified and will not cause digestive distress.
6 - Reduce inflammation.
Some evidence suggests depression may be an allergic reaction to irritation and inflammation in the gut.
- Omega-3 fatty acids have been shown in many studies to reduce inflammation, and are also beneficial for mood.
- White willow bark contains salicin, similar to salicylic acid, the active compound in aspirin; it works by blocking inflammatory chemicals in the body.
- Curcumin, the active ingredient in turmeric, is a powerful anti-inflammatory, suppressing compounds in the body that trigger inflammation.
- Other good inflammation reducers: green tea, boswellia, resveratrol, and pycnogenol.
7 - Eat bone broth.
Homemade stocks from animal bones and cartilage are rich in gelatin, collagen, and amino acids that promote digestive health and heal the lining of the intestines. They're easy to make, and you can find packaged versions of the real thing. Or take those beneficial compounds in supplement form: you'll find gelatin and collagen in capsules or as a powder to mix into smoothies; gelatin powder can also be used as the base for natural gelatin dessert. The main amino acids in bone broth include arginine, glycine, glutamine, and proline; look for these in single or combination forms.
8 - Avoid sugar.
New research shows that a high-sugar diet caused changes in the gut bacteria of mice, impairing their "cognitive flexibility," or the ability to adjust to changing situations. Microbiota alterations also negatively affected their short- and long-term memories, and impacted their performance on mental and physical function tests. Natural sweeteners such as honey, maple syrup, and agave (though better options than white table sugar) have the same impact. Xylitol, erythritol, and other sugar alcohols are indigestible and can cause digestive distress. Your best bet: look for stevia, a natural sweetener derived from a South American herb, available in powders, droppers, and packets.
9 - Ingest a little dirt here and there.
Historically, our gut adapted to interaction with the outside world by ingesting a little dirt here and there; we develop immunity to potential pathogens through low-grade, routine exposure. But modern cleaning products and antibacterial agents wipe out everything, including some beneficial bacteria the body needs. Be choosy about household cleaners; look for nontoxic, natural alternatives, and steer clear of antibacterial ingredients and hand sanitizers (other than natural versions made with essential oils). Or consider a probiotic made from SBO (soil-based organism). SBOs are extremely hardy and can survive stomach acid and heat. They're still a little controversial, but at least one study showed significant improvement in irritable bowel patients.
Medically reviewed by Onikepe Adegbola, MD PhD