HoldsUp

Huberman Lab · 2026-07-27 · Andrew Huberman (host), Anthony Richards, Sarah, Van Spina, Josima, Nick Ferendo, Kelly, Kevin

Your Top Health Questions Answered

52 research-tied claims examined: 1 contradicted 3 overstated 1 context 43 supported 4 unverified

1

Contradicted by research

0:50:41Andrew Huberman (host)contradictedlow

The J-shaped notch on canine nostrils creates a physical airflow dynamic where inhaled odorants are retained and recirculated across space and time.

"Well, if you've ever seen that sort of J-shaped nostril on the dog's nose, it's kind of like little notches on the sides. It creates a physical environment where every inhale keeps the odor in and keeps it circulating. So, they're spending a lot of time with each odor, even if they smelled something a few seconds or even minutes ago." (said at 0:50:41)

The speaker misattributes the function of the lateral notch (alar slit) on the canine nostril and misstates the fluid dynamics of olfaction. Fluid dynamics and anatomical studies show that the external lateral nostril slit functions during expiration by directing expired air laterally and caudally away from the front of the snout, preventing exhaled air from blowing away the external odor plume. Odorant transport to sensory neurons occurs internally via a specialized anatomical olfactory recess located at the posterior nasal cavity. Canine sniffing occurs at high frequencies (roughly 3–7 Hz), and the external notch does not trap and recirculate inhaled odors across minutes.

3

Overstated

0:03:16Andrew Huberman (host)overstatedhigh

REM sleep is critical for inducing neuroplasticity and consolidating learning from preceding days.

"And that REM sleep is critical for a number of things: for inducing neuroplasticity. So any learning that you did in the preceding day or days is going to be consolidated during REM sleep." (said at 0:03:16)

The claim overstates the isolated role of REM sleep by asserting that 'any learning' is consolidated during REM sleep. Extensive human and animal evidence demonstrates that memory consolidation relies on a coordinated interplay between non-REM (NREM) sleep—particularly slow-wave sleep (SWS)—and REM sleep. SWS and its associated neural oscillations (slow oscillations, sleep spindles, and hippocampal sharp-wave ripples) are the primary drivers of systems-level memory reactivation and declarative memory consolidation. REM sleep contributes to synaptic remodeling, emotional memory processing, and schema integration, but it is not the sole or primary stage responsible for consolidating all learned information.

  • context: About sleep's role in memory. (Physiological reviews 2013) · cited 2866x in the literature
    "Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms... Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories." (abstract, passage verified)
    pubmedfull study (doi)
  • contradicts: Differential effects of non-REM and REM sleep on memory consolidation? (Current neurology and neuroscience reports 2014) · cited 260x in the literature
    "In fact, numerous recent studies do provide further support for the crucial role of SWS (or non-REM sleep) in declarative memory consolidation. However, recent evidence for the benefit of REM sleep for non-declarative memories is rather scarce. In contrast, several recent studies have related consolidation of procedural memories (and some also emotional memories) to SWS (or non-REM sleep)-dependent consolidation processes." (abstract, passage verified)
    pubmedfull study (doi)
  • context: Systems memory consolidation during sleep: oscillations, neuromodulators, and synaptic rem… (BMB reports 2025) · cited 7x in the literature
    "Systems consolidation is supported by stage-specific brain oscillations: during NREM sleep, the coupling of slow-oscillations, spindles, and sharp-wave ripples facilitates hippocampal-cortical transfer of memory representations, while REM sleep theta oscillations contribute to memory integration, abstraction, and emotional tagging... At the synaptic level, sleep balances strengthening and weakening of connections through a coordinated interplay of NREM and REM activity." (abstract)
    pubmedfull study (doi)
0:16:29Andrew Huberman (host)overstatedmoderate

Viewing bright ambient daylight within the first hour after waking stimulates a morning peak in cortisol and catecholamines (dopamine, epinephrine, and norepinephrine).

"Any amount of ambient daylight that you can get in the first hour after waking will greatly benefit you. It'll increase your morning cortisol peak... All are going to help increase that morning cortisol peak, lead to larger increases in the catecholamines, dopamine, epinephrine, norepinephrine" (said at 0:16:29)

Controlled laboratory experiments demonstrate that exposure to bright light (specifically short-wavelength, blue-enriched light) during the first hour after waking enhances the cortisol awakening response (CAR) compared to dim or red light. However, the claim is overstated: 'any amount' of light is insufficient to elicit this effect, as dim light conditions show no such stimulation. Furthermore, bundling this mechanism with claims that morning daylight systematically produces large increases in dopamine, epinephrine, and norepinephrine overstates the established human evidence.

0:40:24Andrew Huberman (host)overstatedmoderate

The primary effect of exercise on neuroplasticity and learning is an increase in autonomic arousal that facilitates focus for one to six hours afterward.

"But the most potent effects are by virtue of the fact that exercise increases arousal, which then allows you to focus better in the following one to six hours." (said at 0:40:24)

A single bout of exercise reliably increases physiological arousal and leads to modest, transient improvements in cognitive performance, including attention and executive function, immediately and shortly following exercise. However, claiming that autonomic arousal facilitating focus for 'one to six hours afterward' is the primary or most potent mechanism of exercise on neuroplasticity and learning overstates the evidence. Meta-analyses show that post-exercise cognitive enhancements are typically small to moderate in magnitude and are measured within minutes to an hour post-exercise, returning toward baseline as autonomic recovery occurs. Furthermore, the primary drivers of exercise-induced neuroplasticity and long-term learning involve neurotrophic and structural mechanisms (such as BDNF upregulation, synaptogenesis, and angiogenesis) rather than solely transient acute autonomic arousal.

1

Needs context

1:13:38Andrew Huberman (host)needs contextmoderate

Re-evaluation of large-scale hormone replacement therapy studies shows that HRT provides beneficial effects when initiated early in perimenopause or early menopause rather than later.

"they will conclude that there does appear to be a beneficial effect of certain hormone replacement therapies for perimenopause and menopause if the therapies are started early enough. Meaning if the therapies were started too late, there was some evidence of some detrimental effects perhaps. But if the therapies were started early enough, either in menopause or perimenopause, then there were some beneficial effects observed" (said at 1:13:38)

Re-evaluation of large randomized trials, notably the Women's Health Initiative (WHI), led to the 'timing hypothesis' (or 'window of opportunity' hypothesis) in menopausal hormone therapy. Subgroup analyses and subsequent trials demonstrated that when hormone therapy is initiated early (in perimenopause or within 10 years of menopause / before age 60), the risk-benefit balance is significantly more favorable (showing reductions in menopausal symptoms and fractures, with lower or neutral cardiovascular risks) compared to when therapy is initiated later in older women, where risks of adverse vascular events are increased. However, large randomized trials maintain that hormone therapy is not recommended strictly for primary disease prevention regardless of timing.

43

Supported by research

0:02:30Andrew Huberman (host)supportedhigh

Drinking caffeine within 8 to 10 hours before sleep disrupts sleep, even if a person can fall asleep easily.

"drinking caffeine in the 8 to 10 hours before sleep is going to disrupt your sleep, even if you can fall asleep after caffeine." (said at 0:02:30)

A systematic review and meta-analysis of controlled trials examining caffeine's impact on sleep architecture and duration (PMID: 36870101) found that caffeine consumption significantly reduced total sleep time (by 45 minutes) and sleep efficiency, increased wake after sleep onset, and reduced deep slow-wave sleep (N3/N4). Meta-regression analysis determined that to avoid reductions in total sleep time, a standard cup of coffee should be consumed at least 8.8 hours prior to bedtime. Controlled trials (PMID: 24235903) also demonstrate that caffeine taken hours prior to sleep produces objective sleep disruption even when individuals are unaware of the loss.

0:02:40Andrew Huberman (host)supportedmoderate

Alpha-GPC supplementation increases levels of acetylcholine in the nervous system.

"something that increases levels of acetylcholine. And the most direct way to do that over the counter and the safest way that I'm aware of to do that is to use the supplement Alpha-GPC." (said at 0:02:40)

Preclinical studies demonstrate that administration of L-alpha-glycerylphosphorylcholine (alpha-GPC) delivers bioavailable choline that crosses into the central nervous system to increase acetylcholine synthesis and release in brain regions such as the hippocampus and cortex. In vivo microdialysis and radiotracer studies in rodents show dose-dependent increases in acetylcholine formation and release following alpha-GPC administration.

0:03:28Andrew Huberman (host)supportedmoderate

REM sleep is critical for stripping the emotional load from past memories.

"importantly, REM sleep is critical for removing the emotional load of previous days', not just one day, but days' memories. And if we don't get enough REM sleep, we tend to feel more emotional." (said at 0:03:28)

The statement accurately reflects the 'Sleep to Forget, Sleep to Remember' neurobiological framework and supporting neuroimaging findings. Experimental work examining overnight sleep physiology shows that REM sleep is specifically associated with the depotentiation of amygdala reactivity and a reduction in subjective emotional intensity elicited by previous affective experiences, while preserving the factual memory trace. Disruption of REM sleep or its neurochemical conditions is associated with heightened emotional reactivity and impaired emotional regulation.

  • supports: REM sleep depotentiates amygdala activity to previous emotional experiences. (Current biology : CB 2011) · cited 382x in the literature
    "Specifically, the marked suppression of central adrenergic neurotransmitters during REM (commonly implicated in arousal and stress), coupled with activation in amygdala-hippocampal networks that encode salient events, is proposed to (re)process and depotentiate previous affective experiences, decreasing their emotional intensity... Here, we demonstrate that REM sleep physiology is associated with an overnight dissipation of amygdala activity in response to previous emotional experiences, altering functional connectivity and reducing next-day subjective emotionality." (abstract, results, passage verified)
    pubmedfull study (doi)
0:04:32Andrew Huberman (host)supportedmoderate

Alpha-GPC supplementation potently increases circulating levels of TMAO via biochemical conversion in the body.

"Increasing the amount of choline in your system can after a few biochemical steps increase the amount of TMAO that is circulating in your body. Now TMAO can be increased by any number of things: fish, meat, etc. Anything that increases choline levels can do this, but Alpha-GPC does it pretty potently." (said at 0:04:32)

Human randomized crossover trials and mechanistic animal studies confirm that alpha-GPC (L-alpha-glycerylphosphorylcholine) supplementation significantly and rapidly increases circulating trimethylamine N-oxide (TMAO) levels. Intestinal enzymes and gut microbiota convert alpha-GPC into choline and subsequent trimethylamine (TMA), which is oxidized to TMAO in the liver. Clinical trials comparing choline sources demonstrate that water-soluble forms like alpha-GPC and choline salts cause sharp spikes in circulating TMAO, whereas lipid-bound forms like phosphatidylcholine do not.

0:04:50Andrew Huberman (host)supportedmoderate

High circulating levels of TMAO over time carry cardiovascular risk.

"you don't want too much TMAO consistently over time because it does carry some cardiovascular risk." (said at 0:04:50)

Observational evidence consistently demonstrates that elevated circulating levels of trimethylamine N-oxide (TMAO) are associated with an increased risk of cardiovascular disease, major adverse cardiovascular events (MACE), and all-cause mortality. A 2024 meta-analysis of 30 prospective observational cohorts (n = 48,968) found that elevated TMAO levels were associated with a 41% higher risk of MACE (hazard ratio: 1.41, 95% CI 1.20–1.54) and a 55% higher risk of all-cause mortality (hazard ratio: 1.55, 95% CI 1.37–1.75). While observational association is robust across multiple systematic reviews, whether TMAO is a direct causal mediator or a prognostic/surrogate biomarker continues to be evaluated.

0:04:57Andrew Huberman (host)supportedlow

Regular, high-dose usage of Alpha-GPC over long periods is associated with an increased risk of stroke and other cardiovascular events.

"there was one paper a few years back that suggested that perhaps people who use Alpha-GPC regularly at high dosages, so 900 milligrams multiple times throughout the day over long periods of time, may have increased risk of stroke and other cardiovascular insults." (said at 0:04:57)

The host accurately describes a large 2021 retrospective cohort study from South Korea examining over 12 million adults aged 50 and older. The study found that prescription use of L-alpha glycerylphosphorylcholine (alpha-GPC) was associated with a significantly higher 10-year risk of total stroke (adjusted hazard ratio 1.43 in a matched cohort), ischemic stroke, and hemorrhagic stroke in a dose- and duration-dependent manner. Because the evidence comes from an observational cohort subject to potential confounding by indication, the overall certainty is low.

0:05:21Andrew Huberman (host)supportedlow

Allicin found in garlic can inhibit the gut-mediated production of TMAO.

"Garlic has something called allicin in it, which can inhibit some of the production of TMAO. We don't have time to get into the whole TMAO production pathway, but this has to do with your gut, and a lot of these conversions are done in the gut. And garlic can inhibit that." (said at 0:05:21)

Research demonstrates that allicin, a primary bioactive organosulfur compound in garlic, can inhibit the gut microbial conversion of dietary precursors (such as carnitine) into trimethylamine (TMA) and subsequent trimethylamine-N-oxide (TMAO) formation. In preclinical mouse models and in vitro cultures, allicin remodeled the gut microbiota and inhibited intermediate production of gamma-butyrobetaine and TMA. Furthermore, a preliminary human intervention demonstrated that raw garlic juice intake reduced TMAO formation in individuals with high-TMAO production profiles. Because human data remain preliminary and small in scale, overall certainty is low.

  • supports: Atherosclerosis amelioration by allicin in raw garlic through gut microbiota and trimethyl… (NPJ biofilms and microbiomes 2022) · cited 78x in the literature
    "Allicin supplementation significantly decreased serum TMAO in ʟ-carnitine-fed C57BL/6 J mice, reduced aortic lesions, and altered the fecal microbiota in carnitine-induced, atherosclerosis-prone, apolipoprotein E-deficient (ApoE -/- ) mice. In human subjects exhibiting high-TMAO production, raw garlic juice intake for a week reduced TMAO formation, improved gut microbial diversity, and increased the relative abundances of beneficial bacteria. In in vitro and ex vivo studies, raw garlic juice and allicin inhibited γ-butyrobetaine (γBB) and trimethylamine production by the gut microbiota." (abstract, results)
    pubmedfull study (doi)
0:07:07Andrew Huberman (host)supportedmoderate

Taking a hot shower warms the skin and triggers medial preoptic area neurons in the hypothalamus to lower core body temperature.

"taking a hot shower, by virtue of the fact that you warm up the surface of your body, will trigger neurons in the medial preoptic area of your hypothalamus, which act as sort of a thermostat on your core body temperature and will actually help drive core body temperature down, which is a prerequisite for getting to sleep." (said at 0:07:07)

The host's statement accurately reflects human physiological meta-analytic findings and animal mechanistic studies. Systematic review and meta-analysis data demonstrate that taking a warm bath or shower (passive body heating) 1 to 2 hours before bedtime increases peripheral vasodilation and heat dissipation, accelerating the decline in core body temperature and shortening sleep onset latency. Furthermore, neurobiological research shows that skin warming activates neurons in the preoptic hypothalamic area (including the medial preoptic area and median preoptic nucleus), which act as a central thermostat to trigger NREM sleep initiation and facilitate core body cooling.

0:07:40Andrew Huberman (host)supportedhigh

Deliberately prolonged exhalations activate descending efferent pathways of the vagus nerve to slow heart rate.

"When we do a deliberate exhale, okay, so not just passively exhaling, but when we draw out our exhale like so, you activate a descending portion of the vagus nerve... And one of the main pathways there is to your heart. And when you exhale, you slow your heart rate down." (said at 0:07:40)

The host's statement accurately describes the physiological mechanisms underlying respiratory sinus arrhythmia (RSA) and cardiorespiratory control. During exhalation—and particularly during prolonged exhalation—efferent cardiac vagal pathways (descending parasympathetic fibers originating in the pontomedullary brainstem, including the nucleus ambiguus and nucleus of the solitary tract) increase their firing rate to the heart, which acts on the sinoatrial node to slow heart rate. Studies examining both neurophysiological mechanisms (PMID: 27654879) and prolonged exhalation breathing protocols (PMID: 39180643, PMID: 39050620) demonstrate that deliberate, prolonged exhalation increases vagally mediated cardiac autonomic control (measured via heart rate variability parameters like HF-HRV and RMSSD) and leads to transient heart rate deceleration.

0:09:57Andrew Huberman (host)supportedmoderate

To fall asleep and stay deeply asleep, human core body temperature must drop by about 1 to 3 degrees Fahrenheit, and must increase by 1 to 3 degrees to wake up.

"in order to fall asleep and stay deeply asleep, your body temperature actually has to drop by about 1 to 3°. And in order to wake up feeling refreshed and energized, your body temperature actually has to increase by about 1 to 3°." (said at 0:09:57)

Human core body temperature is regulated by the central circadian clock and undergoes a daily oscillation, decreasing prior to and during sleep onset and rising prior to waking. The typical diurnal amplitude of core body temperature fluctuation in healthy adults is approximately 0.5 to 1.0 °C (1.0 to 1.8 °F, extending up to ~3 °F across individual variations). Manipulations that facilitate a drop in core body temperature (such as evening passive heating followed by cooling) enhance sleep onset and sleep quality.

0:17:36Andrew Huberman (host)supportedhigh

Intrinsically photosensitive melanopsin retinal ganglion cells connect directly to the suprachiasmatic nucleus to set the circadian clock.

"these special cells in your eye, the intrinsically photosensitive melanopsin retinal ganglion cells that literally send a direct connection to your circadian clock, set your circadian rhythm." (said at 0:17:36)

Extensive neurobiological research confirms that intrinsically photosensitive retinal ganglion cells (ipRGCs), which express the photopigment melanopsin, form a direct monosynaptic projection via the retinohypothalamic tract to the suprachiasmatic nucleus (SCN), the master circadian pacemaker in the hypothalamus. These specialized photoreceptors detect environmental irradiance (particularly short-wavelength blue light) and transduce light signals to synchronize and entrain circadian rhythms.

0:18:19Andrew Huberman (host)supportedhigh

Circulating cortisol and daytime alertness chemicals exist in opposite diurnal phase to melatonin.

"And cortisol and all these other stimulatory chemicals that you make, they are in opposite phase to melatonin." (said at 0:18:19)

Circadian endocrine physiology well establishes that circulating cortisol and melatonin operate in roughly opposite diurnal phases. Melatonin secretion rises in the evening, peaks in the middle of the dark/sleep period, and drops to minimal levels during the day. In contrast, cortisol reaches its diurnal nadir around the onset of sleep/midnight and peaks in the morning shortly after waking (cortisol awakening response) before declining across the day.

0:27:09Andrew Huberman (host)supportedhigh

Scientific literature does not support the idea that non-water fluids such as coffee or caffeinated beverages cause dehydration.

"the idea that all fluids that aren't water are dehydrating you, including coffee and caffeine, the literature just doesn't support that." (said at 0:27:09)

Scientific reviews and randomized cross-over trials consistently demonstrate that caffeinated beverages, including moderate consumption of coffee, contribute to daily fluid requirements and do not cause dehydration or net fluid loss in habitual consumers. While high doses of caffeine can exert a mild, transient diuretic effect in non-habituated individuals, standard servings of coffee or tea do not cause fluid loss exceeding the volume consumed.

0:02:05Andrew Huberman (host)supportedmoderate

Moderate-to-high-intensity strength training significantly increases circulating cortisol levels above baseline.

"And your workouts, as you mentioned, are going to be for strength and presumably for some muscle size as well, which suggests that they're going to be of moderate to high intensity, which means that they're going to pretty impressively increase cortisol over its baseline late in the day." (said at 0:02:05)

Moderate-to-high-intensity resistance exercise protocols, particularly those involving moderate-to-high loads, sufficient volume, and moderate rest periods involving large muscle masses, reliably stimulate the hypothalamic-pituitary-adrenal (HPA) axis and elicit significant acute elevations in circulating cortisol levels above baseline immediately post-exercise.

0:11:58Andrew Huberman (host)supportedhigh

Moderate-to-high-intensity exercise causes a substantial acute spike in growth hormone secretion.

"And no, it's not going to completely nuke your growth hormone levels during sleep; you just spiked them tremendously during that workout anyway." (said at 0:11:58)

Extensive human experimental evidence demonstrates that acute bouts of moderate-to-high-intensity exercise (both resistance and endurance exercise) are among the most potent non-pharmacological physiological stimuli for growth hormone (GH) secretion, triggering substantial acute increases in circulating GH concentrations.

0:27:08Andrew Huberman (host)supportedhigh

Urine does not need to be completely clear to indicate adequate hydration.

"People argue how much you need to drink, whether or not your urine needs to be clear or not. It doesn't, by the way, but making sure that you're getting enough fluids." (said at 0:27:08)

Adequate hydration (euhydration) does not require urine to be completely clear. In physiological studies evaluating hydration indices using standardized urine color scales (typically an 8-point scale), euhydrated individuals maintaining baseline fluid intake routinely exhibit light yellow/straw urine (ratings around 2 to 4 on an 8-point scale). For example, Armstrong et al. noted that in healthy, adequately hydrated adults meeting fluid needs, mean urine color ratings were around 4 (with a range of 2–7), and participants rarely (0–2% of the time) exhibited completely clear urine (color 1). Interventions restoring water intake after restriction similarly use a urine color threshold below 4 to indicate adequate hydration rather than requiring clear urine.

0:33:44Andrew Huberman (host)supportedmoderate

Creatine monohydrate supplementation at 5 grams per serving supports muscle strength, performance, and brain health.

"Each serving has 5 grams of creatine monohydrate to support muscle strength and performance, as well as brain health." (said at 0:33:44)

Creatine monohydrate supplementation (commonly dosed at 3–5 g/day) is well documented in randomized controlled trials and systematic reviews to increase intramuscular creatine stores, leading to improvements in muscle strength, high-intensity exercise performance, and training adaptations. In addition to muscle ergogenic effects, systematic reviews and narrative reviews indicate that creatine supplementation supports brain health and cognitive function (notably short-term memory, reasoning, and processing under conditions of acute stress, sleep deprivation, or aging), although evidence for cognitive outcomes is more preliminary and heterogeneous compared to the robust physical performance data.

0:33:53Andrew Huberman (host)supportedmoderate

Calcium HMB supplementation supports muscle recovery and reduces muscle breakdown.

"Calcium HMB to support muscle recovery and reduce muscle breakdown" (said at 0:33:53)

Beta-hydroxy-beta-methylbutyrate (HMB), commonly administered as calcium HMB (HMB-Ca), has been extensively evaluated for its effects on skeletal muscle metabolism and exercise recovery. Evidence summarized in expert consensus guidelines and systematic reviews indicates that HMB's primary physiological actions involve suppressing muscle protein breakdown (inhibiting ubiquitin-proteasome proteolysis) and stimulating protein synthesis. Clinical trials in both athletic and clinical populations demonstrate that calcium HMB supplementation attenuates markers of exercise-induced muscle damage (such as creatine kinase) and aids muscle recovery, particularly during periods of intense training or muscle unloading.

0:33:57Andrew Huberman (host)supportedmoderate

Zinc carnosine supplementation supports and improves the integrity of the gut lining.

"and zinc carnosine to support and improve the lining of your gut." (said at 0:33:57)

Multiple randomized controlled trials and mechanistic studies demonstrate that zinc carnosine supplementation helps maintain and restore gut mucosal integrity. In randomized crossover trials in healthy human volunteers, zinc carnosine significantly prevented increases in intestinal permeability induced by NSAID (indomethacin) administration and truncated exercise-induced intestinal hyperpermeability by stabilizing epithelial tight junction proteins and reducing mucosal injury.

0:35:44Andrew Huberman (host)supportedmoderate

Memories are first encoded in the hippocampus and then sent to circuits in the neocortex for storage.

"memories are encoded, right? They're first made in the structure that we call the hippocampus. You actually have two of them, hippocampi, one on each side of your brain. And then memories once they're formed are kind of pushed out. They're not really pushed out, but they're sent to uh different circuits in the neocortex" (said at 0:35:44)

The speaker describes the classic model of systems memory consolidation (and complementary learning systems theory) for declarative and episodic memories. Under this framework, new memories are initially encoded in the hippocampus—a paired structure located in the medial temporal lobes—and over time are progressively consolidated, reorganized, and integrated into distributed neocortical circuits for long-term storage.

0:39:27Andrew Huberman (host)supportedmoderate

Exercise increases circulating catecholamines (dopamine, epinephrine, norepinephrine) and neurotrophic factors including BDNF and IGF-1.

"And they get these again the catecholamines is a repeating theme, the dopamine, epinephrine, norepinephrine, and circulating. Yes, they increase things like brain derived neurotrophic factor etc. They set you up to learn better in part because of the chemicals and their ability to make your brain connections more plastic." (said at 0:39:27)

Randomized clinical evidence demonstrates that acute intense cardiovascular exercise significantly increases circulating levels of catecholamines (dopamine, epinephrine, and norepinephrine) as well as neurotrophic and growth factors including brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) immediately post-exercise. Furthermore, higher post-exercise concentrations of these factors are correlated with enhanced motor skill acquisition and long-term retention.

  • supports: Acute exercise improves motor memory: exploring potential biomarkers. (Neurobiology of learning and memory 2014) · cited 331x in the literature
    "Plasma levels of brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF-1), epinephrine, norepinephrine, dopamine and lactate were analyzed at baseline, immediately after exercise or rest and during motor practice. The exercise group showed significantly better skill retention 24h and 7 days after acquisition. The concentration of all blood compounds increased significantly immediately after exercise and remained significantly elevated for 15 min following exercise except for BDNF and VEGF." (abstract, results, passage verified)
    pubmedfull study (doi)
0:42:00Andrew Huberman (host)supportedhigh

During learning, making errors sends signals relayed through the cerebellum that prompt neural circuitry to reshape.

"And when you fail, when you screw up, that sends a signal through a very interesting set of circuits that's relayed through your mini brain, as they call your cerebellum in the back that then carries the error signal forward, and then the rest of your brain has to reshape itself." (said at 0:42:00)

Extensive neurobiological evidence supports the role of the cerebellum in error-based learning and circuit plasticity. Classical models of cerebellar function (the Marr-Albus-Ito framework) and modern experimental studies demonstrate that movement errors are conveyed via climbing fibers from the inferior olive to cerebellar Purkinje cells as instructive error signals. These signals drive synaptic plasticity (such as long-term depression and potentiation) within the cerebellum and feed into broader cerebello-cortical loops to adapt and reshape motor and cognitive neural networks.

0:42:13Andrew Huberman (host)supportedhigh

Neural circuit reshaping and memory consolidation physically occur during deep rest and sleep, including slow-wave deep sleep and rapid eye movement sleep.

"And here's a critical point. The reshaping occurs during deep rest, in particular, sleep. Both slow-wave deep sleep and rapid eye movement sleep, which we talked about earlier in this episode. Both are crucial." (said at 0:42:13)

The claim is supported by a large and consistent body of neurobiological literature. Memory consolidation and neural circuit remodeling physically occur across sleep states. During non-rapid eye movement (NREM) slow-wave sleep, coordinated slow oscillations, sleep spindles, and hippocampal sharp-wave ripples drive the replay of neural firing patterns and facilitate systems-level memory transfer to the neocortex. Subsequent rapid eye movement (REM) sleep supports synaptic remodeling, memory integration, and global synaptic homeostasis.

  • supports: Sleep-A brain-state serving systems memory consolidation. (Neuron 2023) · cited 346x in the literature
    "During sleep, memory replay occurs during slow-wave sleep (SWS) in hippocampal assemblies together with ripples, thalamic spindles, neocortical slow oscillations, and noradrenergic activity. Here, hippocampal replay likely favors the transformation of hippocampus-dependent episodic memory into schema-like neocortical memory. REM sleep following SWS might balance local synaptic rescaling accompanying memory transformation with a sleep-dependent homeostatic process of global synaptic renormalization." (abstract, passage verified)
    pubmedfull study (doi)
  • supports: Systems memory consolidation during sleep: oscillations, neuromodulators, and synaptic rem… (BMB reports 2025) · cited 7x in the literature
    "Systems consolidation is supported by stagespecific brain oscillations: during NREM sleep, the coupling of slow-oscillations, spindles, and sharp-wave ripples facilitates hippocampal-cortical transfer of memory representations, while REM sleep theta oscillations contribute to memory integration, abstraction, and emotional tagging... At the synaptic level, sleep balances strengthening and weakening of connections through a coordinated interplay of NREM and REM activity." (abstract, passage verified)
    pubmedfull study (doi)
0:43:33Andrew Huberman (host)supportedhigh

Self-testing is significantly more effective for forming stable memories and long-term retention than repeated reading, taking notes, or highlighting.

"People were given a passage of information to read and they could either do it once, twice, three times, or four times. This has been done with multiple uh iterations in different studies. Some studies included taking notes. Some studies included highlighting. You know, all the different ways that people study information to try and learn. By far the most impactful thing for forming stable memories over time or calling back old memories to keep this memory system thriving was self-testing." (said at 0:43:33)

Extensive cognitive psychology research and systematic reviews consistently demonstrate the 'testing effect' (retrieval practice / self-testing). Repeated testing produces superior long-term memory retention compared to passive or low-utility study strategies such as repeated reading, highlighting, or summarization. In comprehensive evaluations of learning techniques across diverse materials and learner populations, practice testing consistently receives high-utility ratings for durable memory formation, whereas rereading and highlighting demonstrate low utility for long-term retention.

0:48:38Andrew Huberman (host)supportedhigh

Olfactory sensory neurons continuously turn over throughout the lifespan in humans.

"The olfactory neurons, the ones that are critically involved in our sense of smell, not only do they turn over throughout the lifespan. So this is very different than other central nervous system neurons, which you basically get one set for life. There are a few others that turn over, but the olfactory neurons are really the world heavyweight champions of turnover throughout the lifespan. You're constantly turning them over." (said at 0:48:38)

The host's statement that olfactory sensory neurons turn over continuously throughout the lifespan in humans is well-supported. The primary olfactory epithelium in vertebrates, including humans, possesses resident basal stem/progenitor cells (globose and horizontal basal cells) that continuously differentiate into mature olfactory sensory neurons to replace dying neurons throughout adult life, making it one of the classic canonical sites of ongoing peripheral neurogenesis.

0:48:58Andrew Huberman (host)supportedvery low

The turnover and sensory tuning of olfactory neurons is activity-dependent, requiring electrical firing generated by sniffing and odor exposure.

"That turnover and their tuning to particular smells, which translates to your ability to smell, is activity dependent. It requires the electrical activity of those neurons. How do you generate the electrical activity of those neurons? You sniff. Sniffing is what does it and smelling particular odors is what does it as well." (said at 0:48:58)

Preclinical animal models and mechanistic neurobiology studies support the concept that olfactory sensory neuron (OSN) turnover, survival, and sensory representation (population tuning) are activity-dependent processes driven by odor stimulation and airflow. In animal models, deprivation of odor input (such as through naris occlusion or genetic silencing) alters the expression of activity-dependent genes and shifts OSN survival dynamics, while odor exposure enhances the survival and tuning of specific receptor-expressing OSN populations. Because these neurogenesis, turnover, and tuning dynamics are derived from rodent laboratory models, certainty is rated as very low.

0:37:15Andrew Huberman (host)supportedhigh

Smell training protocols involving repeated deliberate sniffing of specific odors can improve olfactory acuity and assist recovery after olfactory loss or injury.

"And a lot of people think they'll never get their smell back, but these sorts of things have been shown to help, especially immediately after the injury. Although there is some evidence that you can get enhanced smell over time. And if you haven't had such an injury, you can really build up your sense of smell." (said at 0:37:15)

Multiple systematic reviews and meta-analyses support the efficacy of olfactory training—a regimen involving repeated, structured sniffing of specific scents twice daily over several weeks or months. Clinical evidence demonstrates that olfactory training significantly improves threshold, discrimination, and identification scores in patients recovering from post-traumatic and post-viral olfactory loss. Additionally, research in healthy individuals shows that olfactory training can enhance baseline olfactory sensitivity and discrimination through neuroplastic mechanisms.

0:37:14Andrew Huberman (host)supportedhigh

In men with excess body fat (greater than 20%), reducing calories to lose body fat increases testosterone and free testosterone levels.

"If a man is carrying excess body weight, if he's starting to carry more than, say, 20% body fat, then he would be wise to cut calories to a submaintenance level and lose some of that body fat, ideally while doing resistance training in order to preserve or even build muscle and bring that body fat percentage down. And that's going to improve his testosterone, free testosterone, and other hormone markers of virility, vitality, and fertility." (said at 0:37:14)

Meta-analyses of clinical trials establish that calorie-restricted weight loss in overweight and obese men significantly increases both total and free testosterone levels, along with sex hormone-binding globulin (SHBG). The magnitude of the increase in testosterone is proportional to the amount of body weight lost.

0:37:43Andrew Huberman (host)supportedmoderate

In men with 15% body fat or less, cutting calories below maintenance for extended periods (e.g., several weeks) reduces testosterone and free testosterone levels.

"However, he pointed out that if a male is, you know, 15% body fat or less, if he cuts calories below maintenance level for too long—so I'm not talking about one or two days per week. I'm talking about consistently across the week, six or seven days per week perhaps, and doing that for two or three or more weeks in order to lower body fat percentage—that's very likely to reduce his testosterone and free testosterone levels." (said at 0:37:43)

Extensive research in lean and normal-weight men (including physique athletes and military personnel) demonstrates that sustained caloric restriction and negative energy balance over several weeks lead to significant reductions in total testosterone and free testosterone levels, frequently accompanied by increases in sex hormone-binding globulin (SHBG) and cortisol. These endocrine alterations reflect down-regulation of the hypothalamic-pituitary-gonadal axis during periods of low energy availability.

0:39:43Andrew Huberman (host)supportedhigh

Exogenous testosterone administration, even at micro-doses below 100 mg per week, suppresses endogenous sperm count due to endocrine negative feedback.

"if you take exogenous testosterone, even a little bit, even if you're quote unquote micro dosing it, so less than 100 milligrams per week or so, it will negatively impact your sperm count. It will negatively impact your sperm count." (said at 0:39:43)

Published clinical and endocrinological literature confirms that exogenous testosterone administration provides negative feedback on the hypothalamic-pituitary-gonadal (HPG) axis. This suppresses the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), depleting intratesticular testosterone and significantly impairing or halting spermatogenesis (often resulting in severe oligospermia or azoospermia), even at physiological replacement doses.

0:39:58Andrew Huberman (host)supportedmoderate

Co-administering human chorionic gonadotropin (hCG) alongside exogenous testosterone therapy can partially to completely prevent or offset the depletion of sperm count.

"It can be partially to completely offset by taking hCG, which is typically taken, you know, something like 500 IUs three times a week. Some people do higher doses, etc., alongside the testosterone therapy." (said at 0:39:58)

Co-administration of human chorionic gonadotropin (hCG) alongside exogenous testosterone replacement therapy (TRT) has been shown to maintain intratesticular testosterone levels and preserve spermatogenesis, preventing the severe suppression of sperm count and azoospermia typically induced by exogenous testosterone alone. In a key clinical study of hypogonadal men treated with TRT plus low-dose hCG (500 IU every other day), baseline semen parameters were maintained during long-term follow-up, no men developed azoospermia, and multiple pregnancies were achieved.

0:41:49Andrew Huberman (host)supportedhigh

If a woman's body fat percentage drops too low, it can lead to complete cessation of menstruation (amenorrhea) and impair fertility.

"But as most everybody knows, if a woman's body fat percentage comes down too far, she may stop menstruating entirely or it could adversely impact fertility in other ways." (said at 0:41:49)

A drop in body fat percentage and low energy availability are well-established causes of functional hypothalamic amenorrhea (FHA) and impaired fertility. In states of low adiposity and negative energy balance, altered adipokine signalling (such as decreased leptin) suppresses hypothalamic gonadotropin-releasing hormone (GnRH) pulsatility, leading to reduced luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release, anovulation, estrogen deficiency, and the cessation of menstruation.

0:52:12Andrew Huberman (host)supportedhigh

Head trauma can shear the olfactory nerve axons as they pass through the cribriform plate, resulting in anosmia.

"Now, if you have a respiratory illness or God forbid someone takes a head hit, the cribriform plate, which is a kind of—it's like a Swiss cheese-shaped bone at the back of the nose where the olfactory neuron axons go through, they can often get sheared off and people can become so-called anosmic." (said at 0:52:12)

Head trauma is a well-established cause of anosmia (loss of smell), with shearing and transection of the delicate olfactory nerve axons as they traverse the perforations of the cribriform plate representing a primary mechanism of injury.

1:02:22Andrew Huberman (host)supportedmoderate

A clinical study by Justin Sonnenburg and Christopher Gardner at Stanford showed that consuming low-sugar fermented foods significantly reduced multiple inflammatory markers.

"This has been shown in a beautiful study from my colleagues Justin Sonnenburg and Christopher Gardner at Stanford University School of Medicine. People were given either a low-sugar fermented food sort of call to action to eat more of those each day or increase their fiber intake pretty markedly... What they saw is that many inflammatory markers were significantly reduced in the low-sugar fermented food group." (said at 1:02:22)

A 2021 randomized prospective trial led by Justin Sonnenburg and Christopher D. Gardner at Stanford University (Wastyk et al., Cell) evaluated 36 healthy adults randomized to either a high-fiber or high-fermented-food diet for 10 weeks (with longitudinal follow-up across 17 weeks). The fermented food intervention led to increased gut microbiota diversity and a widespread reduction in circulating inflammatory markers, including cytokines and inflammatory signaling proteins, whereas the high-fiber diet did not produce a uniform reduction in inflammatory markers.

1:03:24Andrew Huberman (host)supportedmoderate

In the Sonnenburg and Gardner diet study, increasing dietary fiber significantly reduced inflammatory markers in some subjects but increased them in others.

"Whereas in the fiber addition group, they found something interesting. Some people who significantly increased their fiber intake experienced a reduction in inflammatory markers. Others had an increase in inflammatory markers." (said at 1:03:24)

In a 2021 randomized prospective trial led by Justin Sonnenburg and Christopher Gardner (Wastyk et al., Cell), healthy adults were assigned to either a high-fiber or a high-fermented-food diet for 10 weeks (17-week total study period, n=18 per arm). In the high-fiber diet cohort, the overall cytokine response score did not change uniformly, but deep immune profiling revealed distinct individualized trajectories: inflammatory markers decreased in participants with higher baseline gut microbiota diversity, whereas inflammatory markers increased in participants with low baseline microbiota diversity.

1:05:58Andrew Huberman (host)supportedmoderate

Supplementation with L-carnitine and coenzyme Q10 improves sperm motility and sperm and egg quality.

"And that's L-carnitine and coenzyme Q10. Both of which have been shown to—well, in the case of males, to improve sperm motility. Not so much count, but motility and quote unquote quality, because that's a multimetric label, quality, as well as egg quality." (said at 1:05:58)

Multiple systematic reviews and meta-analyses of randomized controlled trials support the claim. In men with subfertility or idiopathic infertility, supplementation with L-carnitine and coenzyme Q10 (CoQ10) significantly improves sperm motility and morphology/quality parameters. In women undergoing assisted reproductive technology (particularly those with diminished ovarian reserve or poor ovarian response), CoQ10 pretreatment is associated with improved oocyte yield, embryo quality, and clinical pregnancy rates.

1:06:29Andrew Huberman (host)supportedhigh

L-carnitine is poorly absorbed when taken orally compared to injectable forms.

"And L-carnitine can be taken orally as capsules. Typically those are higher dosages. So those can be as high as, you know, 500 milligrams or 750 milligrams a day. You don't absorb as much of it when you take it orally. Some people will actually do the injectable form of L-carnitine." (said at 1:06:29)

Human pharmacokinetic studies show that oral supplemental doses of L-carnitine have very low bioavailability (roughly 5% to 18% for doses ranging between 0.5 g and 6 g) due to saturation of carrier-mediated intestinal transport. In contrast, injectable (intravenous) administration achieves 100% systemic availability, directly bypassing the gastrointestinal absorption barrier.

1:08:35Andrew Huberman (host)supportedhigh

Even a slight degree of dehydration diminishes both cognitive and physical performance.

"Even a slight degree of dehydration can diminish your cognitive and physical performance." (said at 1:08:35)

Published reviews and systematic analyses demonstrate that mild dehydration—typically defined as a 1% to 2% loss of body mass or body water—can impair cognitive performance (including attention, concentration, psychomotor tasks, and immediate memory) as well as physical exercise performance capacity.

1:15:28Andrew Huberman (host)supportedmoderate

Steroid hormone changes during perimenopause and menopause alter neural circuit activities in brain regions like the hypothalamus and the hypothalamic-pituitary-adrenal axis.

"And so we know that many hormones have a strong effect on neurons, nerve cells in the circuits of the brain, including the hypothalamus, which regulates all sorts of things: hunger, sleep, body temperature. And yes, it's also involved in anxiety. You have the so-called hypothalamic-pituitary-adrenal axis, which is involved in the production of cortisol. So the short answer is yes, yes, and yes. When hormones change, neural circuit activities change in the short term" (said at 1:15:28)

The speaker's assertion that steroid hormone fluctuations during perimenopause and menopause alter neural circuit activities in brain regions like the hypothalamus and impact the hypothalamic-pituitary-adrenal (HPA) axis is well-supported by neurobiological and clinical literature. Estrogens and derived neurosteroids modulate neural circuitry governing hypothalamic homeostatic functions (such as thermoregulation and energy balance) as well as stress-response pathways via GABAergic regulation of the HPA axis.

1:19:10Andrew Huberman (host)supportedmoderate

Approximately 20 percent of the population has an early-bird chronotype, meaning they are genetically hardwired to wake up and go to sleep early.

"While I would say about 20% of people fall into this category that we call early birds by virtue of chronotype, meaning they are genetically hardwired to prefer to get up very early and to go to sleep very early" (said at 1:19:10)

Population-based circadian and sleep studies standardly report that morning-type individuals (early birds) make up approximately 15% to 25% (roughly 20%) of the population, with intermediate chronotypes making up the majority (~50-60%) and evening types comprising another ~15-25%. Large-scale genome-wide association studies (GWAS) confirm that chronotype is a heritable trait influenced by multiple genetic loci near core circadian rhythm genes (such as PER2 and RGS16), supporting the genetic basis of circadian preferences.

  • supports: Genome-Wide Association Analyses in 128,266 Individuals Identifies New Morningness and Sle… (PLoS genetics 2016) · cited 421x in the literature
    "We performed genome-wide association studies of self-reported chronotype (morning/evening person) and self-reported sleep duration in 128,266 white British individuals from the UK Biobank study. Sixteen variants were associated with chronotype (P<5x10-8), including variants near the known circadian rhythm genes RGS16... and PER2... Our study brings the total number of loci associated with chronotype to 22 and with sleep duration to three, and provides new insights into the biology of sleep and circadian rhythms in humans." (abstract, results, passage verified)
    pubmedfull study (doi)
1:25:04Andrew Huberman (host)supportedlow

Published data demonstrate that patient recovery from surgery and illness in hospitals is significantly improved when the patient is positioned next to a window with natural light.

"There are even data showing that recovery from surgery and illness in the hospital is significantly improved if the patient is next to a window where they get some natural light." (said at 1:25:04)

Published comparative studies support the claim. In a seminal 1984 study of post-cholecystectomy patients, assignment to a room with a window view of nature resulted in shorter hospital stays and lower analgesic requirements compared to rooms facing a brick wall. Subsequent studies of surgical patients found that placement on the sunny/bright side of a unit significantly reduced postoperative pain medication use and perceived stress. Similar benefits on length of stay have been documented in psychiatric inpatient settings for patients in sun-exposed rooms. However, the evidence base is observational and consists of relatively small comparative cohorts, warranting a low GRADE certainty.

1:18:50Andrew Huberman (host)supportedmoderate

The majority of the human population has an intermediate chronotype, naturally preferring to wake up between 6:00 a.m. and 8:00 a.m. and go to sleep between 10:00 p.m. and midnight.

"or the majority of people prefer to get up between 6:00 and 8:00 a.m. and go to sleep somewhere between 10:00 p.m. and midnight. That's just the majority of people in the world." (said at 1:18:50)

Large-scale epidemiological studies evaluating human chronotypes (such as data from the Munich ChronoType Questionnaire database of over 55,000 participants and nationally representative cohorts) show that chronotypes follow a near-normal (Gaussian) distribution. In standard categorical classifications (e.g., the Horne-Östberg Morningness-Eveningness Questionnaire or MCTQ mid-sleep distributions), the majority of the population (typically ~50–60%) falls into the intermediate or 'neither' chronotype category, with typical preferred sleep onsets between 10:00 p.m. and midnight and wake times between 6:00 a.m. and 8:00 a.m. (mid-sleep around 3:00 to 4:00 a.m.).

1:25:20Andrew Huberman (host)supportedmoderate

Regaining previously built muscle mass and strength following atrophy or detraining is significantly faster and easier than building muscle for the first time.

"which is the reestablishment of strength, the reestablishment of hypertrophy when you had it prior. So regaining strength and muscle size is far easier than gaining it for the first time" (said at 1:25:20)

The phenomenon known as skeletal muscle memory—where regaining muscle size and strength after a period of detraining occurs more rapidly than building it initially—is supported by human trials and physiological reviews. Randomized human training-detraining-retraining studies demonstrate that previously trained muscles regain lost cross-sectional area and maximal strength rapidly upon retraining, showing faster rates of initial adaptation than seen during equivalent phases of de novo training. The proposed mechanisms include myonuclear permanence, persistent epigenetic modifications (such as altered DNA methylation), and retained neuromuscular/motor adaptations.

4

No source found (not proven false)

0:03:05Andrew Huberman (host)unverifiedvery low

Alpha-GPC supplementation has been shown to modestly increase REM sleep or not hinder REM and slow-wave deep sleep.

"Alpha-GPC is also one of the few supplements that I'm aware of that can increase the amount of rapid eye movement sleep that you get, REM sleep." (said at 0:03:05)

No published record matching the claim that Alpha-GPC supplementation increases rapid eye movement (REM) sleep was located; this does not prove the claim false.

0:07:49Andrew Huberman (host)unverifiedvery low

Approximately 85% of vagus nerve fibers are ascending sensory fibers, while roughly 10% to 15% are descending motor/efferent fibers.

"Everyone thinks about the vagus nerve like sensory information coming up from the body. That's 85% of the vagus pathway. The other 10 to 15%, no one knows the exact numbers, comes from the brain down to the organs of the body." (said at 0:07:49)

No published record matching the claim that approximately 85% of vagus nerve fibers are ascending sensory fibers and roughly 10% to 15% are descending motor/efferent fibers was located among the retrieved literature; this does not prove the claim false.

0:19:17Andrew Huberman (host)unverifiedvery low

The suprachiasmatic nucleus integrates the total amount of photon/light energy received across the previous two to three days to set circadian timing.

"your suprachiasmatic nucleus, your brain's central circadian master clock that organizes all of this, is literally integrating the number of photons that you saw, light energy, in the previous two or three days." (said at 0:19:17)

No published record matching the claim that the suprachiasmatic nucleus integrates the total amount of light energy received across the previous two to three days was located; this does not prove the claim false.

0:47:47Andrew Huberman (host)unverifiedvery low

Noxious odor detection operates via a distinct, hardwired neural pathway separate from general olfaction that preserves the ability to detect noxious smells even when general olfaction is compromised.

"Let's avoid noxious smells. And I'll tell you why you can avoid noxious smells in this because there's a hardwired pathway for that. You never you actually never uh lose your core ability to detect noxious smells unless you've had some damage to the olfactory system. It's a different pathway." (said at 0:47:47)

No published record matching the claim that noxious odor detection operates via a distinct, hardwired neural pathway separate from general olfaction that preserves the ability to detect noxious smells when general olfaction is compromised was located; this does not prove the claim false.

Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.