How to Optimize Your Brain-Body Function & Health

High-Level Overview

In this solo episode, Andrew Huberman continues his series on the senses with what he calls possibly the most foundational one: interoception, or our "sense of self," the ability to sense what's happening inside our own bodies. He argues it sits alongside sleep as a main determinant of how we feel, focus, perform and even heal. The central idea is that the brain and organs are in constant two-way conversation, mostly through the vagus nerve, and that this conversation carries two kinds of information: mechanical (pressure, stretch, volume) and chemical (acidity, nutrients, carbon dioxide, pathogens). Understanding these signals lets you influence them.

The tone is enthusiastic and teacherly, mixing detailed neuroscience (Piezo receptors, GLP-1R neurons, the area postrema, the OVLT) with jokes about churros, hot dog contests and vomiting. The episode moves through the body organ by organ (lungs and heart, stomach and intestines, the gut microbiome, the vomiting and fever systems) before tying it all back to emotion and a simple heartbeat-sensing exercise. Huberman lays out about 11 practical protocols along the way.

The Discussion Explores:

• A new Stanford study showing fermented foods, not high fiber, increased microbiome diversity and reduced inflammation
• Brain-body communication as a two-way mechanical and chemical dialogue, carried largely by the vagus nerve
• How inhales speed up the heart and exhales slow it down, and breathing patterns for calm, alertness, or being "alert but calm"
• Piezo pressure receptors, carbon dioxide and the urge to breathe, and the Hering-Breuer reflex
• How gut stretch and nutrient-sensing neurons drive hunger, plus a glutamine trick for sugar cravings
• Gut acidity, microbiome diversity, leaky gut, and the nasal microbiome
• Nausea (area postrema), remedies like ginger, and fever (the OVLT) and how to cool the body correctly
• The vagus as a communication system, emotions as body states, and training interoception by sensing your heartbeat

Deep Dive into Main Ideas

Protocol 1: Fermented Foods Beat Fiber for Inflammation

Huberman opens with a finding he calls immediately actionable, from his Stanford colleague Justin Sonnenburg's lab, published in Cell. Healthy adults from varied backgrounds were given either a high-fiber diet or their usual diet plus fermented foods (such as sauerkraut, kimchi, and even fermented cottage cheese). Both groups ramped up to about four to five servings a day, which for fermented foods is only four or five tablespoons of sauerkraut or kimchi. The researchers took repeated stool and blood samples and ran large, unbiased screens of proteins and inflammatory markers.

The result, Huberman says: "the fermented foods far outperformed the high fiber diet." Fermented foods increased the diversity of the gut microbiome and lowered inflammatory markers and markers of autoimmune disruption. High fiber reduced microbiome diversity and, in some people, increased inflammation, though it did increase enzymes that help digest carbohydrates. Huberman stresses that this doesn't mean fiber is bad, only that two to four servings of fermented foods a day is an inexpensive, easy habit worth adopting. He suggests the carbohydrate-digestion finding might also explain why lifelong meat-eaters and plant-based eaters each feel bad when they try the other's diet: how well you use a food may depend on your eating history.

Brain and Body: A Mechanical and Chemical Dialogue

Huberman describes interoception as a sixth sense, turned inward instead of toward the outside world. The main pathway is the vagus nerve, the tenth cranial nerve, whose name comes from the same root as "vagabond because it wanders throughout the body. It isn't really one nerve but a set of superhighways," like Google Maps, carrying signals from the brainstem to the heart, lungs, diaphragm, gut and spleen and back again. Those signals control heart rate, breathing, digestion and even whether the spleen releases immune cells.

Every organ sends two kinds of information: mechanical (Is the gut full or empty? Is the heart beating fast or slow?) and chemical (Is the gut acidic enough? Is carbon dioxide too high? Is there a pathogen?). The one exception is the brain itself. "Your brain has no sensation of its own": it has no pain or touch receptors, which is why brain surgery can be done without anesthetizing the brain tissue. Headaches come from receptors outside the brain. Huberman's core claim is that when you regulate the mechanical and chemical environment of your organs well, your brain works better, including focus, memory, sleep, mood and healing.

Protocols 2 to 4: Using Breathing to Steer Your Heart and Brain

When you inhale, your lungs fill and the diaphragm (a dome-shaped skeletal muscle you can control voluntarily) moves down. That gives the heart a little more room, so blood flows more slowly inside it. The sinoatrial node reports this to the brain, and the brain speeds the heart up. When you exhale, the diaphragm rises, the heart has less room, blood moves faster, and the brain sends a signal through the vagus nerve to slow the heart down. So inhales speed the heart and exhales slow it, a "contract" between organs and brain you can use at will.

Three practical patterns follow. To calm down fast, "emphasize exhales," especially with the physiological sigh: two inhales (ideally through the nose) to fully inflate the air sacs, followed by a long exhale to release as much carbon dioxide as possible. People and animals do this naturally in sleep. To become more alert, emphasize inhales: deep, vigorous inhales with shorter exhales. After 25 to 30 of these, adrenaline rises and you may feel like you've had a couple of espressos. For a middle ground, box breathing uses equal inhale, hold, exhale and hold, each of a few seconds (most people struggle beyond five). Huberman's point is that long breathwork routines are just explorations of these basic mechanics. Once you understand that inhales raise heart rate, exhales lower it, and carbon dioxide and oxygen must stay balanced, you can design your own practice rather than looking for one perfect protocol.

Piezo Receptors, Carbon Dioxide and Protocol 5: Alert but Calm

For the "aficionados, Huberman explains how the body senses lung pressure: Piezo2 receptors in the lungs, part of a family discovered largely in the Scripps lab of his friend Ardem Patapoutian, report how full the tiny air sacs (alveoli) are. Chemically, he stresses that carbon dioxide isn't simply bad." We need oxygen and carbon dioxide in balance. Brainstem neurons trigger the gasp reflex when carbon dioxide in the blood crosses a threshold. We mainly breathe to get rid of carbon dioxide, and taking in oxygen is a byproduct. Raising someone's inhaled carbon dioxide can trigger near-instant panic.

Protocol 5 uses this chemistry. Sitting or lying down, never in or near water, take 25 to 30 deep inhales through the nose with passive exhales through the mouth. You'll feel warm and flushed as adrenaline rises. Then exhale fully and hold your breath with empty lungs for 15 to 30 seconds or longer. Because you've blown off much of your carbon dioxide, the gasp reflex is delayed, and many people can hold for 90 seconds to two minutes or more (free divers use this, but Huberman warns people not to teach themselves free diving). The payoff is a state that's "alert but calm" for about 10 to 20 minutes afterward, useful for anyone who relies on stimulants or ice baths to focus but then feels jittery. He notes this resembles Wim Hof and centuries-old tummo breathing, and says he's trying to explain the mechanisms rather than the names.

He adds the Hering-Breuer reflex: pressure receptors mean that with full lungs your urge to breathe comes later, and with empty lungs it comes sooner. That's why you take a big breath before going underwater, and why swimmers practice being underwater both with full and with empty lungs.

Protocol 6: Gut Fullness, Hunger and Fasting

Huberman reminds listeners that we are "but a series of tubes," and that as embryos we were basically shaped like a churro. The digestive tract, a tube sealed off at intervals by sphincters, uses pressure receptors to tell feeding centers in the brain whether the stomach is full or empty. A very full gut can literally suppress the motor pattern of lifting another bite to your mouth (the "I can't put another bite in my mouth" feeling after Thanksgiving). An empty gut activates hunger neurons in the arcuate nucleus of the hypothalamus that drive reaching for food, somewhat independently of whether you actually need nutrients. He warns that competitive eaters who train by stretching their stomachs with large volumes of water are doing something dangerous.

Stephen Liberles's lab at Harvard found GLP-1R neurons with cell bodies near the neck that send branches into the intestines to sense stretch and how fast food is moving, and other branches up to the brain to promote or stop eating. The practice Huberman suggests is to spend 10 to 20 seconds noticing how full or empty your gut is between meals. He rated his own at about 30 to 40% full during the recording. With practice, this awareness makes it easier to override mechanical hunger signals. That helps self-described "drive-by blueberry" snackers like himself and people doing intermittent fasting (he usually fasts 12 to 16 hours and eats his first meal around 11 a.m. or noon). Recognizing that an empty stomach isn't the same as needing nutrients makes fasting easier, and he cites Satchin Panda's research on fasting benefits such as autophagy.

Protocol 7: Nutrient-Sensing Neurons and Sugar Cravings

Other gut neurons sense chemistry. Liberles's GPR65 neurons and neurons described by Diego Bohórquez at Duke respond to three nutrient types: fatty acids (especially omega-3s from fish, fish oil and krill), amino acids from digested protein, and sugars. They signal the brain to "do more of it" regardless of taste. Even when the mouth is numbed or food is delivered straight to the stomach through a tube, they still drive the desire to eat.

Huberman's protocol for sugar cravings uses this: take about a teaspoon of the amino acid glutamine, or for strong cravings, mix it with a sip or two of full-fat cream. Feeding these neurons amino acids and fat seems to reduce the drive for sugar. He jokes that as a teenager he used to drink half-and-half in the middle of the night. He recommends limiting simple sugars and says omega-3-rich foods or fish oil can also help.

Gut Acidity, the Microbiome and the Nose

Huberman's big point about gut chemistry is that the stomach should be acidic, and bacteria that cause problems thrive in alkaline conditions. He says antacids treat the symptom of reflux, and that the medical view has shifted. Some people now use acidifying approaches to reduce reflux. Whether our mucosal tissues host good or bad microbes depends largely on their acidity. That includes the nose: a human study in Cell Reports found that breathing through the nose most of the time (except when eating, speaking or exercising hard) and avoiding mouth breathing, especially during sleep, improves the nasal microbiome and its ability to fight infection.

The gut microbiome in turn shapes the balance of inflammatory cytokines (TNF-alpha and IL-6, which cause inflammation) and anti-inflammatory ones (IL-10). When the right microbes are present and inflammation is lower, studies show better focus, sleep, resistance to infection and wound healing. Improving the microbiome has also been linked to improvements in autism spectrum disorder symptoms, irritable bowel syndrome, Crohn's disease, Hashimoto's thyroiditis, eczema and age-related muscle loss (sarcopenia). He doesn't claim it cures these conditions, but says it can meaningfully help. The key is diversity: lack of it, called dysbiosis, shows up in chronic illness and long bed rest. He also notes that some people who take lots of probiotics or prebiotics report brain fog, because the goal is diversity, not simply more microbes. And he's skeptical that commercial tests can give meaningful readouts compared with the large lab screens used by researchers like Sonnenburg.

Protocol 8: Leaky Gut, Glutamine and Betaine HCl with Pepsin

Leaky gut, Huberman explains, happens when the "tight junctions" that seal gut cells together like a chain-link fence stop working, which he associates with an overly alkaline gut and the wrong microbes. Food proteins then leak into the bloodstream, the immune system makes antibodies against them, and people can develop what feel like, and effectively become, food allergies. His recommendations are regular fermented foods, and possibly glutamine, one to three teaspoons a day, which a limited number of studies suggest can help, though the mechanism is unclear.

He flags the next practice as controversial and asks for feedback. Some people with digestive, autoimmune or mood issues take hydrochloric acid supplements, usually betaine HCl combined with the enzyme pepsin, starting with one or two partway through a meal and adjusting to avoid excessive warmth in the stomach. He stresses that acids can burn, that it's not a cure-all, that people with healthy digestion don't need it, and that anyone considering it should talk to their healthcare provider first.

Protocol 9: Nausea and the Area Postrema

The brain is protected by the blood-brain barrier, a much tighter version of the gut's fence, because nearly all neurons can't be replaced. (Huberman adds that, contrary to recent news, psychedelics affect plasticity but there's no evidence they cause new neurons to grow.) In one spot in the brainstem, the area postrema, next to the chemoreceptor trigger zone, the barrier is deliberately open so neurons can act "like a crossing guard" sampling the blood. When they detect toxins, pathogens or too much acidity, including excess alcohol, which Huberman calls fundamentally a poison, they trigger the abdominal reflexes of vomiting. These neurons also respond to memories and thoughts, which is why seeing or even imagining vomit can make someone nauseous.

To reduce unwanted nausea, Huberman cites 11 independent studies he found showing that one to three grams of ginger, whether as food or in capsules, reduces nausea. Peppermint may help too. Cannabis (THC and possibly CBD, supported by at least one study) can reduce nausea, likely by raising the threshold at which area postrema neurons fire, which is relevant for chemotherapy patients. He says it's a decision for people to make with their doctors and depending on local laws.

Protocol 10: Fever and Cooling the Body Correctly

Fever is also driven by chemical sensing, from neurons around the brain's fluid-filled ventricles, which sample cerebrospinal fluid. The OVLT (organum vasculosum of the lamina terminalis) detects toxins, bacteria and viruses, or proteins that have ended up where they shouldn't be. It signals the preoptic area of the hypothalamus to raise body temperature. Huberman calls fever adaptive: "fever is there to cook the bad thing," because many pyrogens can't survive high temperatures, so reducing a fever with drugs isn't always the right move. Local inflammation, like the itchy swelling from mosquito bites he got in Texas, is the immune system's histamine response, not the insect's venom.

The life-saving part: at 102 to 104°F you're entering real danger, because heat damages neurons that don't come back. Citing Stanford thermal-regulation expert Craig Heller, Huberman warns that a cold towel or ice pack on the back of the neck or torso is the wrong approach. It cools the blood going to the brain, which may then turn up the heat further. Instead, cool the palms of the hands, the soles of the feet and the upper face, and aim for whole-body cooling.

The Vagus Is a Communication System, and Emotions Live in the Body

Huberman challenges the popular idea that the vagus nerve is purely calming. When you eat amino acids, sugars or fats, vagal signals trigger dopamine and alertness, and nausea and fever are hardly calming. "It's not a calming system it's a communication system," he says, one that also has motor functions. Stress disrupts digestion because it quiets gut-to-brain signaling through the vagus, which then throws off gut chemistry. He refers listeners to his episode on mastering stress.

Emotions, he argues, are largely created by combining signals about the gut, the heart and breathing, not directly by the thought or headline that set them off. That state shows on the face: pupil size, flushing or pallor, frowning or smiling. Studies show that when we know someone well, our heart rate and breathing start to match theirs without our realizing it. He's careful to say this isn't explained by "mirror neurons," which he considers more myth than reality. He admits he deliberately snuck up on the emotion discussion by building up from gut chemistry and breathing.

Protocol 11: Train Interoception by Sensing Your Heartbeat

Unlike vision or hearing, interoception can improve very quickly. The exercise is simple: sit still for a minute or two, close your eyes, and try to feel and count your heartbeats without touching your pulse. If you have a device, compare your count to it. Some people find this easier with lungs empty or during a breath hold. Huberman suspects this is one reason meditation works: shutting off outside input and turning inward strengthens the connection between body and brain. He prefers "interoceptive awareness" to "vagal tone," and says doing this once or twice a week improves mood, focus, enjoyment of food and people, and your ability to notice moments when what feels like losing focus is really just a rising heart rate that a few exhales can bring down.

Conclusion

Huberman presents interoception as the constant conversation between the brain and the organs, carried mostly by the vagus nerve and made up of mechanical and chemical signals. That framework ties the episode's protocols together. Breathe with longer exhales to calm down, stronger inhales to wake up, or cycle deep breathing into a breath hold for "alert but calm." Notice how full your gut is to manage hunger and fasting, and feed nutrient-sensing neurons (glutamine, fats, omega-3s) to reduce sugar cravings. Eat two to four servings of fermented foods a day, keep the gut acidic and the microbiome diverse, and breathe through your nose. Use ginger for nausea, cool the hands, feet and face during overheating, and practice sensing your heartbeat. His broader message is that how we feel emotionally is closely tied to what's happening in our body, and that simple, free practices let us influence both.

This is a summary of "How to Optimize Your Brain-Body Function & Health" from Huberman Lab, giving you the GIST so you can decide if you want the REST. Listen to the full episode.