The “Second Brain”
An estimated 100 million neurons line the gastrointestinal tract, which includes the esophagus, stomach, small intestine, and large intestine. This neural network sends and receives signals using over 30 different neurotransmitters, including serotonin, dopamine, and norepinephrine. The enteric nervous system, often called the “second brain,” is in many ways autonomous, although it can communicate with the brain through the vagus nerve.
The Gut Microbiome
Adding complexity to the story is the presence of the gut microbiome — an ecosystem of bacteria, fungi, viruses, and protozoa that live primarily inside the large intestine, selectively consuming nutrients and releasing a number of compounds into our bodies. The gut microbiome can produce hormones and neurotransmitters and can even stimulate neurons in the enteric nervous system, sending signals to the brain.
These microorganisms are involved in a variety of bodily processes, such as fiber digestion and immune system regulation, as well as metabolism and appetite. They are heavily influenced by diet. Genetics also affect gut microbiome composition, although the physiological mechanisms are not yet understood.
Nutrition and Nutrigenomics
Nutrition affects the microbiome, with prebiotic fibers (such as beta-glucans in oats and inulin in chicory root) being particularly important since they act as food for the microorganisms. Nutrigenomics, the scientific field that studies the interactions between nutrition and genes, also play a role.
For example, a predisposition toward deficiencies in certain vitamins, such as vitamins B6, B12, or D, has been linked to particular genes. Like us, the gut microbiome has specific nutrient requirements (which includes vitamins) and will be negatively impacted if those needs aren’t met.
A DNA Diet
In addition to vitamin levels, genes also affect how individuals process and react to carbohydrates, fat, salt, gluten, caffeine, and alcohol. Since people respond differently to the same foods, the best diet for a healthy gut microbiome is also not one-size- fits-all. However, a diet based on DNA testing can provide personalized nutrition that creates the optimal conditions for a healthy microbiome. For example, a personalized plan designed around nutrigenomics might call for certain probiotics, prebiotics, vitamins, or omega-3 fatty acids, either through diet or supplements.
Links Between Gut Microbiome and Mental Health
The gut microbiome, through its role in biochemical signaling via hormones and neurotransmitters, has been linked to mental health. Recent studies have shown correlations between the gut microbiome and several mental disorders, including:
- Anxiety — probiotics successfully used to reduce anxiety symptoms 1
- Depression — probiotics successfully used to reduce depression symptoms 2 and a correlation found between fecal microbiota and depression 3
- Bipolar disorder — found to be associated with subnormal levels of 2 different species of gut bacteria 4
- Obsessive compulsive disorder (OCD) — found to be associated with subnormal levels and less diversity of gut bacteria 5
- Post-traumatic stress disorder (PTSD) — found to be associated with subnormal levels of 3 different species of gut bacteria 6
- Attention deficit hyperactivity disorder (ADHD) — decreased rates of the disorder found in teenagers when given probiotics in infancy 7
- Asperger syndrome — decreased rates of the disorder in teenagers when given probiotics in infancy 8. One proposed mechanism is that the microbiome influences
- the development of the hypothalamic-pituitary-adrenal axis in early life, which affects stress reactivity later on.
Nutrigenomics for the Best You — Mind and Body
General tips for maintaining a healthy gut microbiome include stress management, the judicious use of antibiotics, and the addition of prebiotics and probiotics to the diet. But for optimal results, a diet based on DNA testing is needed. Knowing about your unique genetic makeup can help you make wiser decisions about diet and supplements to set the stage for optimal mental health. Order your DNA test kit today.