Ever had a “gut feeling”? Do things go better when you trust your “gut instinct”? Scientists prove these phrases make more sense than you may have thought.

Turns out our gut mental health is actually like a second brain. Researchers have even named a part of our nervous system in the gut: the enteric nervous system, or ENS. This system operates independently, but communicates with the central and autonomic nervous systems. The ENS report on conditions in the gut controls secretion of enzymes, and also has profound effects on mental health and mood.

This growing field of research increasingly fascinated scientists and laypeople alike. Some theorize that our microbiomes (the community of microorganisms living in the gut) than our own human willpower may control our actions more. Turns out, gut microbes produce many of the neurotransmitters that we used to associate only with the brain:

“Microbes produce a variety of neurochemicals that are exact analogs of mammalian hormones involved in mood and behavior [8, 55-57]. Over 50% of the dopamine and the vast majority of the body’s serotonin have an intestinal source [58, 59]. Many transient and persistent inhabitants of the gut, including Escherichia coli, [8, 55, 56] Bacillus cereus, B. mycoides, B. subtilis, Proteus vulgaris, Serratia marcescens, and Staphylococcus aureus [60] have been shown to manufacture dopamine. Concentrations of dopamine in culture of these bacteria were reported to be 10–100 times higher than the typical concentration in human blood [60] . . . Certain probiotic strains alter the plasma levels of other neurochemicals. B. infantis 35624 raises tryptophan [a precursor to serotonin] levels in plasma [64]. The lactic acid-producing bacteria found in breast milk and yogurt also produce . . . GABA [66]. GABA activates the same neuroreceptors that are targeted by anti-anxiety drugs such as valium and other benzodiazepines.” (Alcock, Maley, Aktipis, 2014)

Considering that most patients with psychiatric illness also struggle with gastrointestinal issues, treating the gut could have a tremendous impact on one’s mental health.

What specific effects can bacteria have on the brain?

“Bifidobacterium and Lactobacillus are the main genera showing beneficial effects on anxiety- and depression-like behavior“, which is great, since the most commercially available strains are of those types. Mayer, Knight, Mazmanian, Cryan, and Tillisch (2014) summarized benefits from specific strains in mice:

• Treatment in adulthood with Bifidobacterium infantis reduced the effects of early life stress-induced immune changes and depressive-like behaviors (Desbonnet et al., 2010)
• Lactobacillus helveticus ROO52 has been shown to reduce anxiety-like behavior and ease memory dysfunction (Ohland et al., 2013)
• Lactobacillus rhamnosus JB-1 reduced anxiety- and depression-related behaviors during swim and maze tests (Bravo et al., 2011)
• Treatment with Mycobacterium vaccae reduced anxiety and improved performance on a complex maze task (Matthews and Jenks, 2013)
• Bifidobacterium longum normalizes anxiety-like behavior in a colitis model (Bercik et al., 2011a)
• A B. longum, but not L. rhamnosus strain, normalized anxiety-like behavior that was induced by an infection (Bercik et al., 2010)
• A combination of L. rhamnosus and L. helveticus reversed stress-induced memory dysfunction in Citrobacter rodentium-infected mice (Gareau et al., 2011)
• Probiotic treatment has also proved efficacious in alleviating pain responses in animal models (Rousseaux et al., 2007; McKernan et al., 2010)

Basically, the right balance of microscopic bacteria in your belly can reduce anxiety, depression, disordered eating, memory problems, pain responses, and much more. This can even help individuals who do not have a diagnosed mental illness, but want to improve their mental health; one study showed that depression-free young adults who took a combination of Bifidobacterium bifidum, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus casei, Lactobacillus salivarius, and Lactococcus lactis for one month experienced a reduction in aggressive and ruminative thoughts.

How do I adjust my microbiome for mental health?

Much of our microbiome is determined at a very young age, from factors like delivery through a vaginal or C-section birth, breast or bottle feeding, home environment, and more. However, it is possible to adjust your microbiome and improve your health in adulthood. Just keep in mind that your microbiome may have faced setbacks during your life that made you more prone to mental health issues. For example, the more times you have taken antibiotics during your life, the more often you have wiped out your friendly gut flora.

Here are some of the most important things you can do to nourish a healthy gut microbiome:

• Eat fermented foods. Make sure the label says things like raw and “live active cultures”. You can also make almost any fermented food at home if you are careful to prevent molds. Some examples of fermented foods include:
  • Kefir
    Photo by Jess Lander
  • Kombucha
  • Yogurt with active cultures
  • Sauerkraut
  • Pickles
  • Tempeh
  • Kimchi
  • Lactofermented condiments
• Take a probiotic supplement. This is probably necessary if you have taken antibiotics in your life, don’t eat many fermented foods, or have mental health or digestive issues. It’s also just an easy and consistent way to ensure that you’re getting lots of beneficial microbes into your body
• Eat complex carbohydrates from plants. Many of these carbs are prebiotics that act as food for your friendly gut flora
  • Note: You will probably need to exert some willpower over your gut-brain as you get started with changing your diet! Bad bacteria (also known as pathogens) in your gut could hijack your neurotransmitters and make you crave foods that are bad for you. A great example is the yeast Candida albicans. People with an overgrowth of candida crave sugar; sugar is great food for candida, and eating more sugar allows the candida to grow out of control and kill good bacteria!
  • Some great prebiotic foods include:
    • Onions
    • Asparagus
    • Cabbage
    • Legumes
    • Artichokes
    • Chicory
    • Leek
    • Apples
• Exercise. Most of us know it can it improve your mood (thanks endorphins!), but it may also improve the diversity of your gut flora

How do I choose a probiotic supplement?

How many CFUs do I need?

CFUs, or colony-forming units, are the units used to count the number of live, active organisms in a probiotic supplement. For people who do not have any gut, mental health, or immune issues, a supplement with about 5 billion organisms may be enough as maintenance. For anyone who has issues with their gut, mental health, or immune system, choose a probiotic with at least 50 billion CFUs. After you come off of a course of antibiotics, you will probably need an even stronger probiotic to replenish the good flora you lost during treatment.

While billions of units sounds like a lot, remember that there are trillions more bacterial cells in our bodies than human DNA cells, so a few billion CFUs is nothing compared to the vast size of the human microbiome. To make any appreciable difference in your health, you must choose a probiotic with a CFU count in the billions.

Which probiotic strains should I look for?

Which strains you choose depends on the effects you want. It is impossible to review the effects of every single strain, especially since this is a new field of research and scientists are discovering more about the microbiome all the time. To briefly indicate possible strains you might look for, here are a few probiotic strains commonly found in supplements:

• Lactobacillus acidophilus: one strain most commonly found in commercial supplements, L. acidophilus helps support nutrient absorption and digestion of dairy foods. Different strains of the species can have different effects, including strengthening the immune system and reducing signs of emotional distress.
• Saccharomyces boulardii: S. boulardii is actually a yeast, so it is a superb choice to take as maintenance treatment with antibiotics. It can stimulate immunity, prevent diarrhea when traveling, and encourage production of digestive enzymes.
• Bifidobacterium: This genus includes B. lactis, B. bifidum, B. breve, B. infantis, and B. longum. Bifidobacterium performs many of the same functions as Lactobacillus species do, but they also produce acetic acid, which is a short-chain fatty acid. “Acetic acid is more effective at reducing the growth of yeasts and molds than is lactic acid.” Bifido species live in the vagina, urogenitary, and gastrointestinal tract, where they help prevent overgrowth of pathogenic bacteria or yeast.

Working on your microbiome could be one of the best ways to improve your mental health! Try these suggestions, then let us know if your improved gut has led to a better mood!

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