By Dr. Mercola

When you think about strategies to achieve optimal brain performance, you may think about doing crossword puzzles or learning a new language... adding more sleep or even eating more omega-3 fats may also come to mind.

Most people would not automatically think about their gut when they think about brain health... but this is actually a perfect place to look, one that may very well hold the secret to improving your mood, mental health and preventing other brain-related diseases, like Parkinson's.

You may not be aware that you actually have two nervous systems:

Both are actually created out of the same type of tissue.

During fetal development, one part turns into your central nervous system while the other develops into your enteric nervous system.

These two systems are connected via the vagus nerve, the tenth cranial nerve that runs from your brain stem down to your abdomen.

It is now well established that the vagus nerve is the primary route your gut bacteria use to transmit information to your brain. That's right... while many think of their brain as the organ in charge, your gut actually sends far more information to your brain than your brain sends to your gut.

To put this into more concrete terms, you've probably experienced the visceral sensation of butterflies in your stomach when you're nervous, or had an upset stomach when you were very angry or stressed. The flip side is also true, in that problems in your gut can directly impact your mental health, leading to issues likeanxiety, depression, and autism.

For instance, in December 2011 the Journal of Neurogastroenterology and Motility reported the novel finding that the probiotic (good bacteria) known as Bifidobacterium longum NCC3001 has been shown to help normalize anxiety-like behavior in mice with infectious colitis.i

Reportedly, the bacteria's effect on anxiety involves modulating the vagal pathways within your gut-brain connection:

Separate research also found the probiotic Lactobacillus rhamnosus had a marked effect on GABA [an inhibitory neurotransmitter that is significantly involved in regulating many physiological and psychological processes] levels in certain brain regions and lowered the stress-induced hormone corticosterone, resulting in reduced anxiety- and depression-related behavior.ii

When researchers severed the vagus nerve, GABA receptor levels and the animals' behavior remained unchanged after treatment with L. rhamnosus, confirming that the vagus nerve is most likely the primary pathway of communication between the bacteria in your gut and your brain.

Interestingly, just as you have neurons in your brain, you also have neurons in your gut -- including neurons that produce neurotransmitters like serotonin, which is also found in your brain. In fact, the greatest concentration ofserotonin, which is involved in mood control, depression and aggression, is found in your intestines, not your brain! (Perhaps this is one reason why antidepressants, which raise serotonin levels in your brain, are often ineffective intreating depression, whereas proper dietary changes often help.)

There is a close connection between abnormal gut flora and abnormal brain development—a condition Dr. Campbell-McBride calls Gut and Psychology Syndrome (GAPS). GAPS is the result of poorly developed or imbalanced gut flora and may manifest as a conglomerate of symptoms that can fit the diagnosis of autism, attention deficit hyperactivity disorder (ADHD), attention deficit disorder (ADD) without hyperactivity, dyslexia, dyspraxia, or obsessive-compulsive disorder, just to name a few possibilities.

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Dr. Campbell believes autistic children are born with perfectly normal brains and sensory organs, but once their digestive system becomes a major source of toxicity instead of being a source of nourishment, they start to develop autistic symptoms. This theory fits in well with new research published by the American Society for Microbiology, which identified a bacteria (Sutterella) that is unique to the intestines of children with autism.iii

The researchers reported:

Other links between your gut and your brain health have also been established, including:

Through gene profiling, they were able to discern that absence of gut bacteria altered genes and signaling pathways involved in learning, memory, and motor control. This suggests that gut bacteria are closely tied to early brain development and subsequent behavior.

Your gut bacteria are an active and integrated part of your body, and as such are heavily dependent on your diet and vulnerable to your lifestyle. If you consume a lot of processed foods and sweetened drinks, for instance, your gut bacteria are likely going to be severely compromised because processed foods in general will destroy healthy microflora and sugars of all kinds feed bad bacteria and yeast.

Your gut bacteria are also very sensitive to:

Because of these latter items, to which virtually all of us are exposed at least occasionally, it's generally a good idea to "reseed" the good bacteria in your gut by taking a high-quality probiotic supplement or eating fermented foods. This is important for everyone, but imperative if you are a woman who is pregnant, as your newborn depends on you for its initial gut flora. Many women of reproductive age are deficient in a wide range of vitally important probiotic strains—a deficiency that transfers to their offspring, and may set the stage for any number of problems.

Dr. Campbell explains:

Adding injury to insult is the significant decrease in breastfeeding. We now know that breastfed babies develop entirely different gut flora compared to bottle-fed babies. Infant formula never was, and never will be a healthy replacement to breast milk, for a number of reasons -- altered gut flora being one of them.

When you consider that your gut is your "second brain," it becomes easy to see how your gut health can impact your brain function, psyche, and behavior, as they are interconnected and interdependent in a number of different ways. Fortunately, optimizing your gut health is remarkably easy.

Here are my recommendations for optimizing your gut bacteria: