Gut-brain axis
The gut and brain communicate through the gut-brain axis, connecting physically and biochemically. They can influence each other’s health.
The Vagus Nerve and the Nervous System
The vagus nerve is a major link between the gut and brain, transmitting signals both ways. The gut has 500 million neurons connected to the brain through this system. Stress can inhibit vagus nerve signals, leading to gastrointestinal issues, as seen in studies with animals and humans. For example, reduced vagus nerve function was found in people with IBS and Crohn’s disease. In mice, probiotics lowered stress hormone levels, but only when the vagus nerve was intact, highlighting its role in the gut-brain axis and stress regulation.
Neurotransmitters
The gut and brain communicate through neurotransmitters.
Neurotransmitters control feelings and emotions, like serotonin, which affects happiness and body clock.
The gut and its microbes produce many neurotransmitters, including serotonin.
Gut microbes also produce GABA, which regulates fear and anxiety.
Studies in mice show probiotics can boost GABA and reduce anxiety and depression-like behaviors.
How Gut Microbes Impact the Brain
Gut microbes produce chemicals, including short-chain fatty acids (SCFA) like butyrate, propionate, and acetate.
SCFAs are made by digesting fiber and influence brain functions, such as reducing appetite.
Propionate lowers food intake and brain activity related to food rewards.
Butyrate helps maintain the blood-brain barrier.
Gut microbes also metabolize bile acids and amino acids, which may impact brain function.
Gut Microbes Affect Inflammation
The gut-brain axis is linked through the immune system.
Gut microbes regulate immune responses by controlling what enters and exits the body.
Long-term immune activation can cause inflammation, linked to brain disorders like depression and Alzheimer’s.
Lipopolysaccharide (LPS), a toxin from certain bacteria, can trigger inflammation if it crosses into the blood.
High LPS and inflammation are associated with brain disorders such as depression, dementia, and schizophrenia.
Probiotics, Prebiotics & Gut-Brain Axis
Probiotics are live bacteria that offer health benefits, but not all are the same.
Prebiotics, typically fibers fermented by gut bacteria, may also impact brain health.
Probiotics affecting the brain are called psychobiotics.
Both probiotics and prebiotics can help reduce anxiety, stress, and depression.
What Foods Support the Gut-Brain Axis?
Omega-3 Fats: Found in oily fish, omega-3s can boost beneficial gut bacteria and lower the risk of brain disorders.
Fermented Foods: Items like yogurt, kefir, sauerkraut, and cheese contain healthy microbes that can influence brain activity.
High-Fiber Foods: Whole grains, nuts, seeds, fruits, and vegetables provide prebiotic fibers that support gut bacteria and can reduce stress hormones.
Polyphenol-Rich Foods: Foods like cocoa, green tea, olive oil, and coffee contain polyphenols, which enhance healthy gut bacteria and may improve cognitive function.
Tryptophan-Rich Foods: Foods such as turkey, eggs, and cheese are high in tryptophan, which is converted into serotonin, a key neurotransmitter.
Data from :Dietary Guidelines for Indians
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