Dr. Andrew Huberman, Ph.D. is a Professor of Neurobiology and Ophthalmology at Stanford University School of Medicine. His lab focuses on neural regeneration, neuroplasticity, and brain states such as stress, focus, fear, and optimal performance.
Andrew Huberman breaks down the profound effect the gut has on the nervous system. In addition to the anatomy and physiology, you will learn how the gut controls hunger, influences the brain, the definition of a healthy microbiome, and effects of various diets and lifestyle factors.
Host: Andrew Huberman (@hubermanlab)
Note: For full access to publications that are behind a paywall, check out Sci Hub.
Gut: we’re not just talking about the stomach; the gut includes the entire digestive tract from start to finish
Microbiota: bacteria in the gut
Microbiome: bacteria in the gut AND genes the bacteria make
  • The micro-bacteria are so tiny, you could fit several thousand on the head of a pin
The gut and the brain are a bidirectional biological circuit
Your gut and brain are always in communication: your gut influences your brain and the brain influences your gut
Your digestive system begins at your mouth and ends at your anus, sectioned off by sphincters
Microbiotas live in the lumen of the digestive tract and thrive to varying degrees along the length of the path depending on the acidity and environment
You’re constantly making and excreting micro-bacteria
Behaviors and experiences alter microbiota – literally the hands that are on you at birth, how you were born (i.e., C-section versus vaginal), whether you have pets, whether you were allowed to play outside in the dirt, etc.
One of the major determinants of our microbiome is who we interact with and the environment we’re in – including whether we live with animals
Microbiota contribute to the digestion of nutrients
Enzymes are largely responsible for digestion and catalyzation of other cellular events in the digestive pathway
Microbiota changes the way your brain functions by metabolizing or facilitating the metabolism of neurotransmitters
Certain microbiota can improve or diminish your mood: microbiota are converted into various neurochemicals such as gabba and influence the way your brain functions
  • The more diverse one’s microbiome, the less lonely – read more: Association Of Loneliness And Wisdom With Gut Microbial Diversity And Composition: An Exploratory Study – and here – Emotional Well-Being And Gut Microbiome Profiles By Enterotype
Neurons activated in the gut are activated when sugar, fatty acids, and amino acids are present
Nerve cells (specifically called neuropod cells) in the gut are collecting information about what’s there and sending that information up to the brain via the vagus nerve
Neuropod cells sense nutrients, particularly sugar, which activates areas of the brain that cause you to seek out more of that food
The selective preference for seeking out sweet foods occurs even if you can’t taste the food and it is injected straight into the gut
We don’t just like sweet foods – we have a gut sensation below conscious detection
Dopamine in the context of feeding: causes us to seek out more of the sensation of delight and satisfaction from what we ate
The gut is communicating by way of neurons – some of which also release hormones (e.g., PYY, glucagon, etc.)
Ghrelin levels increase with fasting and stimulate the feeling of driving you to seek out food by inducing hormones like epinephrine
Glucagon-like pathway (GLP-1): made by neurons in the gut and brain; it inhibits feeding and reduces appetite (can stimulate with yerba mate tea, avocado, eggs, ketosis, and other food and drink)
GLP-1 and ghrelin are examples of gut-brain signaling mechanisms that adjust appetite and are dependent on diet
Signaling from gut to brain can be chemical (e.g., hormonal) or mechanical
If you eat or drink too much so you’re full and distended, information travels to the brain via mechano-sensors and activate areas of the brain involved in stopping eating and the “vomit center”
Chemical and mechanical signals are always working in tandem, sending signals to the brain to eat more or stop eating
Gut microbiota are capable of influencing metabolic events and synthesizing neurotransmitters
Indirect signaling: the food you eat and the environment of the gut microbiome can create chemical substrates that allow your brain to feel one way or another
Particular gut microbiota can create dopamine in the gut which enters the bloodstream and changes baseline levels of dopamine in the brain and body
Other microbiota can create serotonin and determine levels of serotonin released during certain events
The majority of serotonin is manufactured in the gut and released by neuromodulators in the brain in response to touch or social experiences
Creating the correct
The things we come into contact within the first three years of life has a profound impact on the microbiota we carry within our body
Babies do not get much, if any, exposure to microbiota in the womb
The gut microbiome is established in days and weeks following delivery – vaginal birth versus C-section, breastfed versus bottle, held by multiple caregivers or just one, pets at home or not, premature baby in NICU or not, etc.
The diversity you create early in life for your children is critical for establishing a healthy gut-brain connection and immunity
Fecal transplants are being performed in research settings to explore the effects of the microbiome for health – for example, transferring fecal matter of a healthy individual into someone with colitis to reset microbiota
The complexity of probiotics:
  • Gut microbiome diversity is critical – but excessive intake of probiotics can induce brain fog – check out: Brain Fogginess, Gas And Bloating: A Link Between SIBO, Probiotics And Metabolic Acidosis
  • Most probiotics don’t actually increase the gut microbiota you need most – unless you’re eating the right foods which can encourage the proliferation
  • Probiotics can be useful during prolonged periods of fasting which disrupts the microbiome – BUT – when you eat, there may be a compensatory mechanism
How to enhance microbiome: get deep sleep, maintain proper social interactions, limit prolonged stress and stressors
High fiber diets may be useful for overall health but don’t necessarily lead to increased gut biodiversity  
Though fiber doesn’t have an impact on gut biodiversity, some people experience a decrease in inflammatory markers which is useful
Diets high in fermented foods (4-6 ounces per day) increase gut biodiversity and decrease inflammatory signals and activity
The consistency of ingesting fermented foods matters more than the number of servings per day – in other words, regularly consuming fermented foods matters more than making sure to hit 4-6 ounces per day
Focus on low sugar fermented foods with live active cultures: plain yogurt (not fruit flavors), kimchee, sauerkraut, Kiefer – note: pickles rarely have ferment
Look for high-quality fermented foods in the refrigerated section – you can also make them at home for more cost-effectiveness
  • For tips, check out: The 4-Hour Chef: The Simple Path To Cooking Like A Pro, Learning Anything And Living The Good Life by Tim Ferriss
When starting to increase fermented food intake, increase servings over time and spread throughout the day to limit any gastric distress you may initially have  
There is evidence in animal models that ingesting artificial sweeteners such as sucralose can disrupt the gut microbiome