Four years ago, my sweet yoga instructor departed this life after battling depression for decades. So I am personally intrigued by research indicting that the health of our gut microbiome can influence our mental health, including conditions like depression. This discovery has spurred the creation of a field of study know as nutritional psychiatry.
Our gut is home to trillions of microorganisms—bacteria, viruses, fungi, and other microbes—that form what’s known as the gut microbiome. These microbes play a critical role in digesting food, producing essential nutrients, and regulating immune function. But their influence extends beyond the digestive system and into the brain, creating what is often referred to as the “gut-brain axis.”
The gut-brain axis is a complex communication network that links the central nervous system to the gut. It allows signals to travel between the gut and the brain via the vagus nerve, hormonal pathways, and our immune system. These interactions affect our mood, behavior, and even cognitive function. People with depression often have dysbiosis with a lower diversity of beneficial bacteria (probiotics) and an overgrowth of harmful pathogens in their gut.
Depression is often treated with selective serotonin reuptake inhibitors (SSRI), a class of drugs designed to make serotonin (a feel-good hormone) more accessible to the brain. But where does serotonin come from? Interestingly, as much as 95% of the serotonin in our system is produced by our gut.
So, what can we do to improve both our gut and mental health? The key lies in nourishing the gut with a balanced, nutrient-rich diet. According to a 2023 article in the journal Pharmaceuticals, “Plant protein, unsaturated fats, and fiber encourage a healthy gut flora compared to excessive animal protein intake, saturated fats, and simple or artificial carbohydrates.”
Fermented foods (such as yogurt, kefir, and kimchi) that contain live beneficial bacteria are an important first step. To keep healthful bacteria alive and flourishing, we want to feed them a wide variety of fiber-rich fruits and vegetables. Aim to eat 30 different types of plants a week. Remember that seasonings such as cinnamon, garlic, ginger and parsley count toward your total. Avoid sugar, which promotes the growth of proteobacteria associated with inflammation.
Before you reach for a bottle of probiotics, it is important to note that only a subset of the trillions of microorganisms in our gut can survive the manufacturing process. Over-the-counter supplements typically offer a combination of only seven: Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus. Plus, as researchers have noted, taking a nutrient in isolation may not have the same beneficial effect as consuming whole foods.
Beyond diet, another way to nurture the gut microbiome is through exposure to the natural world. Research suggests that spending time outdoors in environments rich in diverse microbes, such as soil and fresh air, can positively influence the gut flora. Contact with soil, plants, and nature can introduce beneficial microbes that help maintain a balanced microbiome and support immune function. This is why gardening, hiking, or even walking barefoot on natural surfaces can have a beneficial impact on both gut and mental health.
The gut-brain connection works both ways. Chronic stress, anxiety, and other mental health struggles can negatively affect gut health by disrupting the gut’s microbiome, potentially leading to digestive issues like irritable bowel syndrome (IBS) and further exacerbating mental health problems. So, spending time outdoors engaging with nature, also supports our microbiome by reducing stress.
The growing evidence of the gut-brain connection highlights the importance of caring for our digestive health to support overall well-being. By adopting a gut-friendly lifestyle, including mindful nutrition and outdoor exposure, we may not only improve our digestion but also help to better manage mental health concerns like depression.
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