Research has shown that emotions are not solely determined by the brain but are also influenced by the microbes in the gut, which play a role in regulating moods.
If you're surprised that the microbial ecosystem in the gut can affect someone's emotions, you're not alone. It's scientifically proven! There are around hundreds of trillions of microorganisms inside and outside the human body, with a whopping 99% residing in the gut. By altering the composition of this microbial ecosystem, you can stabilize your mood, boost your immune system, improve sleep quality, and even alleviate mental conditions like depression, Parkinson's, and hyperactivity. In 2013, Science, a prestigious scientific journal, recognized microbial research as one of the top 10 scientific breakthroughs. Scientists continue to validate the profound impact of intestinal microbiota on human health across various domains, signaling increased investment in this area of research for the future.
The gut is a wellspring of thought and joy.
The intestines, often referred to as the "second brain" or "abdominal brain," harbor an autonomous "enteric nervous system" (ENS) responsible for vital digestive functions. With 500 million neurons, the enteric nervous system constitutes the largest nervous system beyond the brain. Apart from regulating digestion, the gut houses numerous neurotransmitters capable of cognition, emotion, and sensation.
Approximately 95% of the body's happy hormones are located in the gut.
Two crucial happy hormones that consistently impact people's mood and emotions are dopamine and serotonin.
Dopamine: This neurotransmitter is associated with emotions, generating feelings of pleasure and serving as the wellspring of love, motivation, and creativity.
Serotonin: This neurotransmitter can instill feelings of happiness, equilibrium, and steadiness. It plays a role in regulating mood, sleep, appetite, and body temperature in the brain, subsequently impacting the functioning of the cardiovascular and endocrine systems.
The intestine produces approximately 95% of the body's serotonin, and about 50% of dopamine is synthesized there as well. Hence, it's reasonable to conclude that when the gut is happy, the brain is happy too.
The brain and intestines are linked through the "gut-brain axis"!
The central nervous system of the brain and the enteric nervous system have complex and close information transmission, and the two organs will affect each other. Emotional overeating, satisfaction from food, nervousness, anxiety, gastrointestinal symptoms caused by stress, such as stomach pain, diarrhea, constipation, etc., these are all symptoms caused by the interaction between the brain and intestines. The bridge responsible for the connection and coordination between the two is called the "gut-brain axis". The "gut-brain axis" refers to the interaction of intestinal bacteria with the intestinal nervous, immune, endocrine, and other systems, affecting the brain and changing thinking and behavior. The axis covers the vagus nervous system, the intestinal immune system, intestinal microbial metabolites, and the HPA axis, and the intestinal bacteria are connected to the brain through these four pathways.
| Vagus nervous system The vagus nervous system serves as the communication link between the brain's central nervous system and the enteric nervous system. It facilitates communication between gut bacteria and the enteric nervous system in the gut, transmitting messages to the brain. |
| Intestinal immune system The intestinal immune system secretes various cellular hormones that are transported to the brain through the bloodstream. Intestinal bacteria play a role in triggering the secretion of these hormones. |
| Intestinal metabolites A small fraction of intestinal bacteria produce substances that influence nerve activity, such as GABA, dopamine, and nitric oxide. These substances enter the bloodstream and elicit various nerve responses in the brain. Additionally, when intestinal bacteria metabolize fiber, they generate acetic acid, propionic acid, and butyric acid. These acids help maintain the acidity of the intestine, inhibiting the growth of harmful bacteria. They also serve as the primary energy source for intestinal cells, nourishing them to sustain intestinal integrity and support immune functions. |
| HPA axis (hypothalamus-pituitary-adrenal) When the brain perceives stress, it triggers the activation of the HPA axis. This leads to the release of stress hormones such as adrenaline, initiating the body's fight-or-flight response. Concurrently, it regulates various functions including digestion, endocrine activity, immunity, and mood to cope with stress. These reactions directly or indirectly impact the balance of intestinal bacteria. |
The gut, often referred to as the "second brain," operates independently, gathering information, making decisions, and issuing commands. Upon receiving messages, it communicates with the brain via the gut-brain axis, resulting in various bodily reactions such as pain and discomfort. Besides its digestive role, the intestine utilizes neurotransmitters like serotonin to influence the brain through this axis, triggering emotional responses that affect memory, learning, sleep, and judgment. This connection has implications for conditions like autism, Tourette's syndrome, Parkinson's disease, and dementia. Thus, the gut-brain axis plays a crucial role in shaping mood and overall health.
