The Microbial Heroes of the Gut-Brain Axis

The connection between your gut microbes and your brain is known as the gut-brain axis. This amazing and humbling relationship allows bacteria in your gut to improve—or destroy—your mood, cognition, and memory. The beneficial microbes, along with the food that supports them, are called psychobiotics. The name was coined in 2013 by professors Timothy (Ted) Dinan and John Cryan at University College Cork in Ireland.

Lactobacilli and Bifidobacteria are at the top of the psychobiotic list.

Source: Courtesy of Scott C. Anderson

When I heard about their work, I contacted them to write a book about this fascinating topic, and they agreed. A year later, National Geographic published it and titled it The Psychobiotic Revolution. The book goes into great detail about the history, mechanics, and future of psychobiotics. The name seemed a bit hyperbolic at the time, but as research pours in, it has proven to be prophetic. So, two of the heroes of the gut-brain axis are Ted Dinan and John Cryan. They are truly revolutionary thinkers.

But there are two groups of bacteria deserving of hero status as well: Lactobacilli and Bifidobacteria. Specific strains of these two bacterial genera have gained star billing. In particular, Lactobacillus helveticus, Lactobacillus plantarum, Lactobacillus rhamnosus, Bifidobacterium longum, and Bifidobacterium breve have shown great promise as psychobiotics. Supporting characters include Faecalibacterium prausnitzii and Akkermansia muciniphila. Some of these are recognizable as the bacteria that produce yogurt, and, indeed, yogurt has shown efficacy in improving mood.

Also included in the range of psychobiotic substances are prebiotics. These are foods for our microbial protagonists, and they include oligosaccharides—chains of sugar molecules that our bodies can’t digest, but our microbes can. Among them, fructo-oligosaccharide and galacto-oligosaccharide are standouts.

Unlike living microbes, prebiotics are easy to store and can encourage the growth of your own home-grown versions of psychobiotics. That may actually make them a better supplement than the microbes themselves.

How They Work

Psychobiotics work in multiple ways:

1. Psychobiotics heal the gut.

A leaky gut is a loose term referring to an excess of normal permeability. A leaky gut can allow toxins and bacteria to infiltrate the entire body, including the brain. Although there is a blood-brain barrier to keep out most invaders, a chronic infection can weaken these defenses, and inflammation can lead to anxiety and depression. Psychobiotics produce butyrate, an amazingly effective balm that both nourishes and heals the delicate tissue that lines the gut. So, by protecting the gut lining, inflammation can be kept at bay, allowing the brain to function optimally and in good spirits.

2. Psychobiotics calm the immune system.

Psychobiotics are friends of your immune system. Some, like Bifidobacteria, have been with you since the beginning. They are actually part of a bacterial sampler that your mother provided in her breast milk. During the first 1,000 days of your life, your immune system learns from this starter kit that certain microbes are to be tolerated. Bifidobacteria and Lactobacilli top the list. Just their presence can calm the immune system and keep it from overreacting to a (possibly benign) infection. As you become weaned, you lose a lot of these microbes, but you can revive your system with ferments like kimchi and yogurt.

3. Psychobiotics talk to the brain.

Psychobiotics are psychoactive! Intriguingly, microbes produce neurotransmitters like dopamine, serotonin, and GABA. These are some of the most potent psychoactive drugs in use. These chemicals are used to communicate with other microbes, but also to communicate with us. Nerve cells in the gut connect to the brain via the vagus nerve that meanders past all of your organs. The brain monitors and controls your organs this way, but it’s a two-way conduit: Your microbes can speak to your brain as well. This means microbes can directly affect your cravings, your appetite, and your mood.

How to Take Advantage of Them

1. Eat a varied diet.

All signs point to diversity of microbes as a proxy for health. Ecologists would not be surprised by this. They know that a varied population has built-in redundancy and is, therefore, more resilient.

So how do you encourage a diverse microbiota? Simply by eating a diverse set of foods. The Mediterranean diet is an exemplar of variety and is associated with a good microbiota, health, and long life. Someone eating Mediterranean-style would not find it unusual to consume 30 different vegetables each week. Give it a try!

2. Eat ferments.

Fermented foods like yogurt, kimchi, kombucha, sauerkraut, and kefir are filled with our psychobiotic stars. Because they are foods, they contain both prebiotics and probiotics. Studies have demonstrated that ferments like yogurt can improve attitudes and even make beneficial physical changes to the brain.

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3. Try supplements.

If you find it difficult to eat 30 different veggies a week, you might want to supplement with prebiotics and probiotics. The label will tell you if your probiotic has the right stuff. For a prebiotic supplement, look for one with a rich mixture of oligosaccharides and flavonoids. That will ensure that you support the diversity that is so important to a healthy gut.

Bottom Line

The bottom line is that two genera of bacteria encompass several important psychobiotics. They are not hard to find, and as they make your gut more resilient, they can boost your mood and cognition. Merely tweaking your diet to include greater variety could pay off big time with these champions of the gut-brain axis.