The human body is a complex ecosystem made up of trillions of microorganisms, including bacteria, viruses and fungi. The collection of microorganisms living in and on the human body is known as the microbiome. Research suggests the microbiome plays a part in both physical and mental health, although much of that research is still early. This article explores what we know so far about microbiome diversity and mental health, and what we do not.
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Call or text 9-8-8 (Suicide Crisis Helpline, 24 hours). If you or someone else is in immediate danger, call 911. In BC you can also call 1-800-784-2433 (1-800-SUICIDE) any time, or 310-6789 (no area code) for mental health support. The Healing Oak is not an emergency service.
What is the Microbiome?
The microbiome is the collection of microorganisms that live in the human body, particularly the gut. The gut is home to an especially rich and varied community of bacteria, fungi and viruses. The microbiome plays a part in digestion, metabolism and immune function.
Why looking after your overall health matters
Looking after your general health is important for several reasons, including:
- •Quality of life: Good health can make it easier to enjoy daily activities, relationships and hobbies.
- •Lower risk of chronic disease: A balanced diet, regular exercise and avoiding smoking can help lower the risk of chronic diseases such as heart disease, diabetes and some cancers.
- •Mental well-being: Looking after your body can support how you feel day to day.
- •Energy and stamina: Eating well and staying active can help with energy levels and physical endurance.
- •Sleep: Healthy habits can support better sleep, which matters for overall health.
- •Immune function: A healthy lifestyle supports your immune system.
Microbiome Diversity and Mental Health
Researchers are studying the gut-brain axis, a two-way communication network between the gut and the brain. The gut microbiome appears to communicate with the brain through several routes, including the vagus nerve, the immune system and hormones.
Some large studies have found links between gut bacteria and mental health. In a 2019 study of 1,054 people in Belgium, published in Nature Microbiology, two groups of gut bacteria (Coprococcus and Dialister) were found at lower levels in people with depression, even after the researchers accounted for antidepressant use. The authors noted that these are associations and that other factors can confuse the picture.
You may have read that gut bacteria control serotonin and dopamine, two brain chemicals involved in mood. The real picture is more modest. In a 2015 study in mice published in Cell, gut bacteria helped control how much serotonin cells in the gut produced, and that serotonin affected gut movement and blood platelets. The study did not look at mood. The 2019 Belgian study found that the ability of some gut bacteria to make a substance linked to dopamine was associated with better mental quality of life. Neither study shows that changing your gut bacteria will change your mood.
What about probiotics and prebiotics? A 2019 review of 34 clinical trials in Neuroscience and Biobehavioral Reviews found that probiotics had small effects on symptoms of depression and anxiety, while prebiotics did not differ from placebo. The authors said more trials in people with diagnosed mental health conditions are needed.
How to support microbiome diversity
There are several everyday habits that may support a varied microbiome, including:
- •Eating a wide range of foods, particularly plant foods that are high in fibre and prebiotics
- •Limiting highly processed and sugary foods
- •Considering probiotic or prebiotic supplements, after talking with your doctor or pharmacist (the US National Center for Complementary and Integrative Health notes the risk of harmful effects is greater for people with severe illnesses or weakened immune systems)
- •Taking antibiotics only when they are prescribed for you, and following your prescriber's directions
- •Managing stress through mindfulness, meditation and exercise
Ten ideas researchers are exploring
- •The gut-brain axis is a two-way communication network that connects the gut and the brain.
- •The gut microbiome appears to communicate with the brain through the vagus nerve, the immune system and hormones.
- •Some studies link a more varied microbiome with better mental well-being, though these are associations.
- •A varied microbiome may help keep inflammation in check, and inflammation is being studied as one factor in some mental health conditions.
- •Gut bacteria can influence chemicals such as serotonin in the gut, but how this relates to mood in people is not yet clear.
- •The microbiome may interact with the body's stress response system, known as the hypothalamic-pituitary-adrenal (HPA) axis.
- •The microbiome may influence brain development in early life, an area researchers are still studying.
- •The gut microbiome interacts closely with the immune system.
- •Researchers are studying whether a varied microbiome may help buffer some of the effects of stress.
- •Probiotics show small effects on symptoms of depression and anxiety in some trials, and prebiotics have not shown a clear effect.
Foods that may support microbiome diversity
- •Yogurt: Yogurt with live and active cultures contains bacteria that may support a healthy microbiome.
- •Kefir: Like yogurt, kefir is a fermented dairy drink that contains live cultures.
- •Sauerkraut: Made from fermented cabbage. Unpasteurized versions contain live cultures.
- •Kimchi: A traditional Korean dish of fermented vegetables.
- •Tempeh: A fermented soybean product.
- •Miso: A traditional Japanese seasoning made from fermented soybeans.
- •Kombucha: A fermented tea drink that may contain live cultures.
- •Jerusalem artichoke: A root vegetable high in inulin, a prebiotic fibre that feeds gut bacteria.
- •Garlic: Contains prebiotic compounds.
- •Onions: Like garlic, onions contain prebiotic compounds.
Resources for Microbiome Health
Many resources are available if you are interested in learning more about microbiome health and mental health. Here are a few examples:
The Canadian Digestive Health Foundation offers resources and information about digestive health, including the microbiome.
The Canadian Mental Health Association provides information and support for people living with mental health concerns.
The Centre for Addiction and Mental Health (CAMH), a mental health and addiction teaching hospital in Toronto, shares information about mental health conditions and treatment.
Can Manual Osteopathy Impact Gut Biome Health?
Manual osteopathy is a hands-on therapy that focuses on the relationship between the body's structure and how it functions. It does not directly change the gut microbiome, and there is no good research showing that it does.
Some manual osteopathic practitioners share general suggestions about sleep, stress and activity, and may suggest you see a nutrition practitioner for diet advice.
Research on manual therapy for gut conditions is limited. A 2014 systematic review of five small trials found that osteopathic treatment may ease symptoms of irritable bowel syndrome (IBS) for some people in the short term, but the authors called the evidence preliminary. Our post on manual osteopathy and IBS explains more.
Conclusion
The microbiome is an active area of research, and the gut-brain axis may help explain some links between digestion and mood. For now, the evidence is early. Eating a varied diet with plenty of fibre and some fermented foods is a reasonable habit for overall health, but it is not a treatment for depression or anxiety.
If low mood or anxiety is affecting your sleep, work or relationships, talk to your doctor or a counsellor. Our pages on anxiety and depression explain where counselling fits.
If you would like help with food choices, diet and nutrition support is available at our Chilliwack and Abbotsford clinics. You do not need a referral to book. Session lengths vary. Fees vary by practitioner. Confirm the fee when you book. Direct billing depends on the practitioner. Ask when you book.
This article is general information, not medical or psychological advice. For advice about your situation, talk to a qualified practitioner.