your gut is your second brain

All disease begins in the gut, said Hippocrates about 2,500 years ago. What does that even mean? Our gut is composed of trillions of bacteria, fungi, viruses, and parasites that regulate our immune system and control the function of our brain. 

There are roughly 100 trillion bacterial cells versus about 30 trillion human cells in the body. You can say that we are more microbial than human! The gut is also called the enteric nervous system, containing 500 million neurons (5x as many neurons as in your spinal cord) that communicate with the central nervous system via the vagus nerve and prevertebral ganglia. Basically, our gut produces more neurons than parts of our nervous system. 

The gut microbiome has many important functions including digesting fiber, regulating our immune system, and controlling brain health. Bacteria-digesting fibers produce short-chain fatty acids, such as butyrate, that have been found to have anti-inflammatory, antitumorigenic, and antimicrobial effects that reduce risks of developing cancer, diabetes, obesity, and heart disease. The gut also regulates our immune system by communicating with immune cells and controlling how our body responds to certain infections. Additionally, the gut produces neurotransmitters such as serotonin, dopamine and melatonin that communicate with our brain. Much of anxiety, depression and sleep problems are caused by imbalances in the gut microbiome. In fact, over 90% of serotonin is produced in the gut! 

There are multiple things that can negatively affect our gut: method of birth, antibiotics, chronic stress, poor diet, aseptic environment, and smoking. It has been found that babies born vaginally have more bacterial diversity compared to babies born via c-section. Antibiotics not only kill the bad bacteria, but also the good ones and destroy the microbiome. Chronic stress has been linked to GI issues such as constipation, diarrhea, ingestion, upset stomach, and in more serious cases, IBD, IBS and GERD. Additionally, a poor diet composed of high amounts of sugar and processed foods (the standard American diet) contributes to low microbial diversity and development of disease. Our ever-growing fear of bacteria and viruses has led to increased use of antibacterial sanitizers and soaps, which kills both good and bad bacteria, decreasing microbial diversity and increasing susceptibility of developing a chronic illness. Lastly, smoking has been found to alter microbial diversity in the gut, leading to increased risk of developing disease. 

What diseases/disorders are associated with an unhealthy gut?

  • Inflammatory bowel disease (IBD)
  • Obesity
  • Diabetes
  • Heart disease
  • Metabolic syndrome
  • Alcoholic and nonalcoholic fatty liver disease
  • Cirrhosis
  • Cancer
  • Autism
  • ADHD