Gut Feelings and Well Being
How a “Second Brain” in our Belly Affects Mood and Well-Being
How many times have you followed your gut? The relationship between the health and functioning of our stomach and digestive track and our mental health and wellbeing is increasingly pointing to a second brain in the gut that involves the gut-brain axis. This gut-brain axis is where the gastrointestinal tract and the central nervous system exchange messages using the same neurotransmitters, serotonin and GABA, which also regulate mood and awareness. Our gut is also home to a thriving population of microbes, tens of trillions of microorganisms, including at least 1000 different species of known bacteria. There are at least as many and perhaps twice as many microbes living in and on our bodies than there are cells that make up our body.
These microbes play a vital role in the regulation of our digestion and mental health. Based on the latest research, changes to the population of the microbes in our gut are associated with metabolic disorders such as obesity, diabetes, and possibly neuropsychiatric disorders such as schizophrenia, autism spectrum disorder, anxiety, and major depression. Over the past few years new neuro-scientific research has shown that gut health is critical for the development of brain systems. Some of the microorganisms found in the gut are capable of producing the neurotransmitters, serotonin and GABA, which can directly affect the central nervous system (CNS). Some preclinical rodent studies suggest that certain probiotics may even have antidepressant and antianxiety effects. The feeling of having butterflies in your stomach is caused by a network of neurons lining the gut that is so extensive it’s rightfully called a second brain. This second brain is responsible for the butterflies we feel when we’re anxious to perform and interacts directly with the microbes that aid in our digestion and also help regulate our immune system and CNS.
It’s not philosophy or critical inquiry that’s happening in the gun-brain axis but a more immediate concern involving the breakdown of food, the absorption of nutrients, and the expelling of waste. All three of these processes requires constant chemical processing, mechanical mixing, and the rhythmic contraction of muscles that moves everything from the mouth, through the stomach, small intestines, large intestines, and ultimately out. This complex array of reflexes and sensory organs make up the second brain and help coordinate gut behavior without involving the brain and CNS. This is similar to how the heart beats independently but is regulated by the brain. More research is needed to fully understand the role and complexity of this so called second brain but the emerging and surprising view suggests it goes far beyond simply processing the foods we eat.
Our interest in using probiotics to supplement and prebiotics to support the healthy microbes in our gut in order to promote overall health and wellness is on the rise. Yet the first probiotic treatment for depression was actually implemented in 1910. So what’s old is new again as we look to support and promote healthy microbes in our gut by feeding them prebiotics which are nutrients intended to nourish the bacteria in our gut rather than our bodies directly. Probiotics are active bacterial organisms intended to populate the gut with healthy, beneficial organism.
The effects of the gut microbes on human health will continue to be an area of research as scientists explore a new class of “psychomicrobiotics” which aims to treat mental illnesses with beneficial microbes. There is evidence that a poor diet is a risk factor for depression further stressing how important a healthy diet is for overall health and wellbeing. Regulating the health of gut microbes using diet, pre- and probiotics may have important benefits for preventing disease and promoting mental health. Better understanding of the relationship between the brain in our heads and the second brain in our gut could help us better understand and treat psychiatric disorders and the overall relationship between the brain and the rest of our body.
The consequence of this second brain is that we quite literally feel the health and activity of our gut in the same way that we experience our other senses and in turn can directly influence our conscious experiences. The whole system is incredibly complex, in fact more information is sent from the gut to the brain than is sent from the brain to the gut. Much of our emotional state is likely influenced by the signals being sent from our gut to our brain. The more obvious links between feeling nervous and nauseous may depend on more subtle messages being sent between the brain and the gut.
While it may be some time before doctors are routinely prescribing beneficial microbes to patients with serious mental health or intestinal disorders, clinical trials have begun on some of the most promising applications including c-diff and Crohn’s disease. We know that in the brain, lesions are associated with various diseases however similar research hasn’t been done on the network of neurons that make up the second brain. For instance we still don’t know exactly how the gut regulates the immune system but it seems likely that it will involve the endocannabinoid system (ECS). The ECS is highly expressed throughout the gut and is well known to be a modulator of the immune system. This is important because most of our immune response is aimed at preventing harmful microbes in the food we eat from infecting and causing diseases in our bodies.
In order to maintain the delicate balance between our immune system and the beneficial microbes that live in our gut, constant communication is necessary using the same neurotransmitters our brain uses. It seems likely that in the future we will need to look beyond the brain in our head to understand and treat the physical and mental ailments that affect so many. As such it may be more important than ever to listen to your gut.
