Dr. Charles Zuker, Ph.D., is a Professor of Biochemistry, Molecular Biophysics, and Neuroscience at Columbia University and an Investigator with the Howard Hughes Medical Institute. Dr. Zuker is the world’s leading expert in the biology of taste, thirst, and craving.
Andrew Huberman and Dr. Charles Zuker discuss the neural circuits of taste, the “gut-brain axis,” the basis of food cravings, and the key difference between wanting (craving) and liking (perceiving) sugar.
They break down taste, food satiety, the damage down by highly processed foods, and more.
Host: Andrew Huberman (@hubermanlab)
Where to find Dr. Zuker: Columbia Zuckerman Institute, Lab website, Howard Hughes Medical Institute (HHMI) profile
The brain weights 2% of body mass but consumes 25-30% of the body’s energy
Perception: neurons only understand electrical signals so there needs to be a reconciliation of understanding the world
Individuals perceive the world differently depending on how we transform these signals, even given the same sensory cues
Perception divides our responses into seeking, avoiding, or tolerating
Detection: cells interacting with the brain directly, think of something touching the tongue
The brain has to compute, encode, and decode taste
The five basic tastes detectable by humans: sweet, sour, salty, bitter, umami (e.g., seaweed, tomatoes, cheese)
Dietary practicality of the five basic tastes:
Sweet: energy
Umami: protein and essential nutrients
Salt: electrolyte balance
Bitter: prevent ingestion of toxic chemicals
Sour: prevent ingestion of spoiled foods
Taste is a hardwired system, but you can train to like something
Detectors in the tongue activate entire programs depending on the taste stimulated and lead us to either recoil or seek more
Myth: taste receptors are relegated to specific parts of the tongue
Every taste bud in the oral cavity has receptors for all of the five basic tastes
The flavor does not equal taste – flavor is the experience of tastes coming together with smell, texture, temperature, vision
It’s possible there are additional tastes, such as fat (but this is really more of a textural stimulation), metallic (we don’t like to eat it but we know what it tastes like)
When you burn your tongue on hot food or beverage, taste receptors and somatosensory cells are disrupted but will be renewed
Sweet vs. bitter: diametrically opposed flavors which evoke different behaviors
Sweet has a positive valence independent of flavor and quality – sweet activates the amygdala
Bitter has a negative valence and evokes aversive behaviors
Conditioned taste aversion: you can train animals to change the nature, quality, and meaning of a stimulus as a function of its state
Perception and craving for sugar happen at multiple stages: (1) receptors in tongue sensing sugar which seek more as they become desensitized; (2) loss of signaling by continuous activating of circuit
Sugar activates reward-pleasure centers in ways that dramatically change our internal state
The body tells the brain what you need
The brain monitors & modulates the state of all organs and systems in the body to ensure everything works together to achieve healthy physiology
The brain creates associations that food is coming & signals to the pancreas to release insulin in anticipation
The vagus nerve innervates the majority of organs in the body, monitors function, sends signals to the brain, and responds accordingly
The vagus nerve carries thousands of fibers with different meanings associated with their specific task
The brain is the conductor of the physiology of orchestra and metabolism
Like versus want: “liking” sugar is a function of the taste system (sweet); “wanting” sugar is a function of the gut-brain axis
Gut-brain axis drives sugar preference: mice will drink exponentially more from sugar versus water if given the choice; once sweet receptors are removed, it will still drink sugar because mouse learned behavior and detects it via smell, location, etc.
Sugar is recognized on its own then cells in the intestine cell signal to the brain via vagal ganglia which reinforce desire and pursuit
Sugar, fat, and amino acids are essential nutrients for all animals
The taste system gives us immediate recognition, but the gut-brain axis reinforces it only when the brain doubles down
Highly processed foods highjack the gut-brain axis, continuously reinforcing “wanting”
We have a destructive reliance on foods that are not healthy
Processed foods are already broken down so your system doesn’t have to work in the same ways it would if the food were natural