The Influence of Gut Biome on Mood

We are obsessed with our gut. Think about the jargon that includes stomach or gut references: "I hate your guts," "You make me sick to my stomach," "The thought of you gives me butterflies," "I have a gut feeling," and so on. It is difficult to sit down for dinner while watching the news without seeing an ad for medication to treat constipation or irritable bowel syndrome. Yes, we love and hate our gut, but we can’t live without it. Our gut plays very important roles in our daily functioning. You know about the gut’s role in digestion and elimination, but did you know it also plays a part in immune function and mood modulation?

We are born with a second brain that resides in our gut called the enteric nervous system. The second brain is intimately tied to the brain in our head. This relationship began when we were just a bundle of cells. Immature cells can develop into different types of organs and organ systems. Very early on in the development of an embryo, a primitive structure called the neural crest grows the cells that ultimately become your brain and spinal cord. This same primitive structure creates cells that develop into the enteric nervous system. There is a direct connection between these two structures, and information flows in a bidirectional way from one to the other.

Given this intimate relationship, it is not surprising that the health of your gut can influence your mood and vice versa. What you eat directly influences the makeup of bacteria in your gut—known as the microbiome—which in turn impacts your health. A healthy gut helps prevent chronic diseases like heart disease and cancer and can reduce inflammation, which has been linked to depression.

A recent study in Frontiers in Psychiatry describes the results of treating two patients who suffered from treatment-resistant depression with fecal microbiota transplants. The gut microbiota composition appears to be altered in depressed individuals who have a predominance of harmful bacteria and less beneficial bacteria in their biome. Although the study size was small, both patients showed significant improvement in their depressive symptoms without side effects after four weeks.

The SMILES trial was the first intervention study to test dietary improvement as a treatment strategy for mild to moderate depression. "SMILES" was a 12-week trial that utilized two parallel study groups. One group had individual nutritional counseling along with their usual form of treatment for depression (medication, psychotherapy, or medication plus psychotherapy). The second group (control) did not have nutritional counseling, but instead had social support sessions that were the same length and frequency as those in the study group. Results showed the dietary support group demonstrated significantly greater improvement between baseline and 12 weeks.

Why is diet so important in brain function including mood regulation? Because gut health is increasingly understood as critical for brain health. Just as diversity is important in populations and ecosystems, it is critically important in maintaining a healthy gut biome. Generally, fiber is lacking in Western diets, and this influences the population and diversity of bacterial species that comprise the microbiome. Modifying behavior such as dietary choices is one way to modify your genetic predisposition to disease.

In 2018, The World Journal of Psychiatry published the results of their study, analyzing food nutrients to arrive at an antidepressant food scale. The Antidepressant Food Score (AFS) was designed to identify the most nutrient-dense individual foods to prevent and promote recovery from depressive disorders and symptoms. They include the following:

Antidepressant animal foods

• Oysters
• Fish roe
• Lobster
• Emu
• Snapper
• Crab
• Clams
• Herring
• Salmon
• Goat
• Snail or whelk
• Smelt
• Liver and organ meats
• Tuna
• Poultry giblets
• Bluefish
• Mussels Spot fish
• Wolf fish
• Pollock

Antidepressant plant foods

• Watercress
• Pumpkin
• Cauliflower
• Kohlrabi
• Red cabbage
• Broccoli
• Butternut squash
• Papaya
• Strawberry
• Dandelion greens
• Brussels sprouts
• Lemons
• Acerola
• Fresh herbs
• Spinach
• Chicory greens
• Mustard, turnip, or beet greens
• Lettuces
• Peppers
• Swiss chard
• Kale or Collards

These are steps you can take to help create a healthy biome:

• Eat a wide range of foods, particularly fruits and vegetables that contribute to diversity in your gut.
• Eat fermented foods such as yogurt, sauerkraut, tempeh, and kefir, which are good sources of healthy bacteria.
• Eat foods high in polyphenols (plant compounds) such as almonds, green tea, and dark chocolate to help lower inflammation.
• Limit artificial sweeteners, which can have a negative effect on blood sugar and insulin response and negatively affect your gut biome.
• Consider adding a probiotic supplement to your diet.
• Maintain a regular sleep routine. One study demonstrated microbiome diversity improved with sleep efficiency and total sleep time.