HoldsUp

Huberman Lab · 2026-07-20 · Andrew Huberman (host), Tommy Wood

Accelerate Learning & Increase Cognitive Capacity | Dr. Tommy Wood

78 research-tied claims examined: 3 contradicted 5 overstated 4 context 65 supported 1 unverified

3 Contradicted by research
1:17:38Andrew Huberman (host)contradictedmoderate

Nattokinase supplementation can naturally help reduce LDL cholesterol.

"As a result, I decided to start supplementing with nattokinase, which can naturally help reduce LDL cholesterol, and it did." (said at 1:17:38)

A systematic review and meta-analysis of randomized controlled trials (RCTs) found that nattokinase supplementation does not reduce LDL cholesterol. In pooled analyses of RCTs, lower doses were associated with a statistically significant slight increase in LDL-C compared to control (MD = 6.49 mg/dL), while higher doses showed no significant difference in LDL-C levels compared to controls. Additionally, double-blind RCT evidence demonstrates that lipid-lowering effects observed in commercial supplement formulations are driven by co-ingredients such as red yeast rice (which contains natural statin compounds like monacolin K), whereas nattokinase alone does not produce a significant reduction in LDL cholesterol compared to placebo.

1:39:35Tommy Woodcontradictedlow

Circulating BDNF does not cross the blood-brain barrier into the brain.

"though circulating BDNF doesn't actually get into the brain" (said at 1:39:35)

Preclinical transport studies directly contradict the assertion that circulating BDNF cannot enter the brain. Experimental pharmacokinetic investigations in animal models (e.g., Pan et al., 1998) demonstrated that intact BDNF in the peripheral circulation rapidly and completely crosses the blood-brain barrier into brain parenchyma via a saturable, high-capacity transport mechanism.

1:40:05Tommy Woodcontradictedhigh

A randomized trial in older adults showed that Norwegian 4x4 high-intensity interval training produced superior improvements in hippocampal function and structure maintenance compared to moderate-intensity training, with benefits maintained for 5 years.

"And the third group did a high-intensity interval training intervention, which is the Norwegian 4x4 protocol... But what they showed was that that high-intensity interval training group, they improved their fitness just as well as the zone 2 group, interestingly, but they had much better improvements in hippocampal function and maintenance of hippocampal structure on an MRI scan. And they maintained that benefit for 5 years after the six-month intervention." (said at 1:40:05)

The speaker appears to refer to the brain MRI substudies of the Generation 100 trial (a randomized controlled trial in older adults aged 70–77 comparing 5 years of Norwegian 4x4 HIIT, moderate-intensity continuous training [MICT], and national physical activity guidelines). The speaker makes multiple factual errors that contradict the published findings: (1) the intervention was a 5-year randomized trial, not a 6-month intervention followed for 5 years; (2) HIIT did not produce superior preservation of hippocampal structure—in fact, the 5-year intervention and post-intervention follow-up showed greater hippocampal volume loss in the HIIT group compared to controls following national guidelines, with the control group showing the lowest rate of hippocampal volume loss over time; and (3) long-term cognitive tests for hippocampal-dependent memory (verbal memory, pattern separation) showed no superior benefit for the HIIT group over the other groups.

5 Overstated
0:27:50Tommy Woodoverstatedmoderate

Meta-analyses of dance interventions in older adults indicate that ballroom and line dancing produce the greatest improvements in cognitive function among physical activity modalities.

"the best evidence is for ballroom and line dancing, which generally requires—and so there are meta-analyses of these interventions in older adults showing that ballroom and line dancing have the greatest effect on cognitive function." (said at 0:27:50)

Meta-analyses of randomized controlled trials demonstrate that dance interventions have a modest to moderate positive effect on cognitive function in older adults. When comparing dance subtypes, a 2025 Bayesian network meta-analysis found ballroom dancing was the most effective dance modality for global cognition (SMD = 0.89), whereas other dances (such as tango or square dancing) primarily improved balance, mobility, or mental health. However, asserting that meta-analyses prove ballroom and line dancing produce the 'greatest effect' across physical activity modalities overstates the literature: overall dance effect sizes on cognition are modest (g = 0.27), and systematic reviews note that evidence is currently insufficient to definitively rank dance types or declare dance superior to all other physical activity modalities.

0:58:44Andrew Huberman (host)overstatedlow

Having a smartphone in close proximity, even if placed in a bag beneath one's chair and turned off, significantly impairs cognitive performance and focus.

"Are you familiar with this recent study about phone on the table, phone in the bag? We would just remind people that if your phone has to be out of the room, even if it's in your bag beneath your chair turned off, [GUEST1: you can still focus, but there's a cost.] HOST: Your cognitive flexibility, etc., really suffer." (said at 0:58:44)

The host is referencing the prominent 'brain drain' study by Ward et al. (2017), which reported that the mere physical presence of a smartphone (on a desk or in a bag, even when turned off or silenced) reduced available working memory capacity and attentional control compared to leaving it in another room. However, stating that cognitive function 'really suffers' significantly overstates the strength and consistency of the evidence. Subsequent pre-registered direct replications (such as Hartmann et al., 2022) failed to replicate the effect across all conditions, and meta-analytic evidence reveals substantial heterogeneity with mixed effects across different cognitive domains.

1:49:23Andrew Huberman (host)overstatedmoderate

A moderate-intensity resistance training or cardio session transiently triples or quadruples baseline cortisol levels.

"It was interesting to me to dive into the literature on cortisol and find that a moderate-intensity resistance training session or cardio session, probably a little bit easier than the 4x4, will triple one's baseline levels of cortisol, like or quadruple it." (said at 1:49:23)

While exercise can stimulate the hypothalamic-pituitary-adrenal axis to elevate cortisol, the claim that moderate-intensity cardio or resistance training triples or quadruples baseline cortisol levels substantially overstates the magnitude of this response. Exercise intensity research establishes a threshold effect (typically around 60% VO2max), where 30 minutes of moderate-intensity exercise (60% VO2max) elevates circulating cortisol by approximately 40% (1.4-fold) and low-intensity exercise (40% VO2max) causes little to no increase. Even vigorous exercise at 80% VO2max increases cortisol by ~83% (less than a doubling). Multi-fold increases (3x to 4x) typically occur only under extreme exhaustive or high-intensity, short-rest protocols, not routine moderate-intensity sessions.

1:53:16Tommy Woodoverstatedmoderate

White matter makes up approximately 60% of the human brain, which is a higher proportion than in other species.

"In the human brain, white matter makes up approximately 60%, more than most other species—any other species." (said at 1:53:16)

The speaker overstates both the proportion of white matter in the human brain and the uniqueness of this proportion compared to other species. In humans, cerebral white matter comprises roughly 40% to 50% of total brain volume (and ~50–60% of the telencephalic/forebrain volume depending on anatomical boundary definitions), with gray matter constituting the remaining majority. Furthermore, comparative neuroanatomy demonstrates that white matter scaling follows a universal allometric power-law relationship (exponent ~4/3) across mammals: as brain size increases, white matter volume scales disproportionately faster than gray matter to maintain connectivity. Consequently, human white matter volume matches allometric predictions for a primate of our brain size, and larger-brained mammals (such as elephants and large cetaceans) possess equivalent or higher proportions of subcortical white matter.

2:00:26Tommy Woodoverstatedmoderate

Studies using a one-week creatine monohydrate loading protocol show significant increases in brain creatine concentrations.

"So, some of the studies that use traditional creatine monohydrate and look at creatine levels in the brain, they did use a loading protocol for a week and then you see significant increases in brain creatine." (said at 2:00:26)

The speaker claims that studies using a 1-week creatine loading protocol show significant increases in brain creatine concentrations. In contrast to skeletal muscle (where a 5-7 day loading protocol reliably increases creatine concentrations by ~20%), brain creatine uptake is much slower due to the blood-brain barrier and endogenous synthesis. Landmark 1H-MRS studies showing significant brain creatine increases typically used multi-week supplementation protocols (e.g., 20 g/day for 4 weeks in Dechent et al. 1999). RCTs specifically evaluating 7-day loading protocols (e.g., in healthy youth, PMID 28079396) failed to find significant increases in brain creatine levels. Thus, stating that a 1-week loading protocol results in significant brain creatine increases overstates the speed and evidence of brain creatine accumulation.

4 Needs context
0:19:35Tommy Woodneeds contextlow

Cognitive visual or auditory processing speed training improves cholinergic signaling in the forebrain.

"And they've done some other studies showing that that kind of training improves cholinergic signaling in the forebrain, which we know is susceptible to the processes of dementia." (said at 0:19:35)

Perceptual learning and computerized cognitive training engage the basal forebrain cholinergic system (including the nucleus basalis of Meynert), which provides the primary cholinergic innervation to the neocortex and is vulnerable to neurodegenerative dementias. In humans, randomized trials of cognitive training show modulation of nucleus basalis functional connectivity in individuals with mild cognitive impairment. In animal models, perceptual and auditory discrimination tasks recruit cortically projecting cholinergic circuits. However, direct evidence that speed-of-processing training broadly enhances forebrain acetylcholine signaling in humans relies primarily on functional connectivity neuroimaging proxies and translational animal models rather than direct in vivo measurements of acetylcholine release.

0:41:52Andrew Huberman (host)needs contextlow

The anterior midcingulate cortex maintains its size in super-agers who take on difficult cognitive or physical challenges.

"we've talked about the anterior midcingulate cortex, the structure that maintains size in super-agers who take on hard things" (said at 0:41:52)

Structural neuroimaging studies consistently demonstrate that 'super-agers' (older adults who maintain memory performance comparable to young adults) have preserved cortical thickness and volume in the anterior midcingulate cortex (aMCC) and salience network nodes compared to typical older adults. Furthermore, neuroimaging frameworks (e.g., Touroutoglou et al., 2020) identify the aMCC as a central hub regulating tenacity and the cost-benefit calculations required to engage in effortful cognitive and physical challenges. However, evidence connecting the maintenance of aMCC size specifically to engaging in 'hard things' is theoretical and correlational; there are no randomized interventional trials demonstrating that taking on difficult challenges causally preserves aMCC volume in older adults.

0:56:20Tommy Woodneeds contextlow

Research by Gloria Mark demonstrates that frequent external distractions habituate the brain to interruptions, causing individuals to self-distract even in the absence of external interruptions.

"And again, I return to Gloria Mark's work. She wrote an excellent book called Attention Span if anybody's like really interested in this. But you get used to a pattern of distraction such that when you're not actually being distracted, you will distract yourself, right?" (said at 0:56:20)

Gloria Mark (an informatics and human-computer interaction researcher, author of the 2023 book 'Attention Span') and colleagues have extensively documented in observational workplace studies and computer interaction research (e.g., CHI conference proceedings and subsequent human-interaction literature) that roughly half of workplace interruptions are self-initiated (internal interruptions or self-interruptions), and that people frequently switch tasks even without external triggers. In medical and workplace literature (such as Tai-Seale et al., 2021, on which Mark is a co-author), knowledge workers and clinicians exhibit very high baseline rates of rapid attention switching. However, asserting that frequent external distractions 'habituate the brain' to cause individuals to self-distract is a mechanistic framing derived primarily from observational and behavioral field studies rather than formal neurobiological habituation trials. The claim accurately describes Mark's core findings and thesis regarding self-interruption patterns, but qualifies as 'context' due to the observational nature of the workplace behavioral evidence rather than controlled neuroscientific habituation data.

2:02:38Tommy Woodneeds contextmoderate

A study in veterans with traumatic brain injury administered 60 grams of branched-chain amino acids daily, split into three 20-gram doses across the day.

"So in one study they did in veterans, they had I think it was three doses of 20 grams spread across the day." (said at 2:02:38)

In a randomized, double-blind, placebo-controlled pilot trial of Veterans with traumatic brain injury (TBI), participants received a total of 60 grams of branched-chain amino acids (BCAAs) daily for 21 days. However, the dosing schedule was 30 grams twice daily (b.i.d.), rather than three 20-gram doses across the day.

65 Supported by research
0:00:00Tommy Woodsupportedmoderate

A study in older adults comparing low-intensity exercise, zone 2 treadmill exercise three times a week, and the Norwegian 4x4 high-intensity interval training protocol for 6 months found that HIIT produced equivalent fitness improvements to zone 2 but resulted in superior hippocampal function and structure maintenance on MRI, with benefits maintained for 5 years.

"There's a much more recent study that took again older adults and randomized them across three different groups. One was like a low-intensity group. Another group basically did kind of zone 2 type work on a treadmill three times a week. And the third group did a high-intensity interval training intervention which was the Norwegian 4x4 protocol... Three times a week for 6 months... they improved their fitness just as well as the zone 2 group, interestingly, but they had much better improvements in hippocampal function and maintenance of hippocampal structure on MRI scan. And they maintained that benefit for 5 years after the six-month intervention." (said at 0:00:00)

A 2024 randomized controlled trial by Blackmore et al. (PMID: 39012673) evaluated 151 healthy older adults (aged 65–85) randomized to low-intensity training (LIT), medium-intensity continuous training (MIT, continuous treadmill), or high-intensity interval training (HIIT, Norwegian 4x4 protocol) 3 times weekly for 6 months (72 supervised sessions). The study found that while both continuous and interval training improved fitness markers, only the HIIT group exhibited significant improvements in hippocampal-dependent learning (paired associative learning), preserved hippocampal volume on 7T MRI (abrogating normal age-related volumetric decline), and enhanced functional connectivity. These cognitive and hippocampal benefits were retained for up to 5 years of follow-up.

  • supports: Long-Term Improvement in Hippocampal-Dependent Learning Ability in Healthy, Aged Individua… (Aging and disease 2024) · cited 24x in the literature
    "Participants, aged 65-85 with no cognitive deficits, were randomly assigned to one of three exercise interventions (low (LIT), medium (MIT), and High intensity interval training (HIIT), respectively). Each participant attended 72 supervised exercise sessions over a 6-month period... After 6 months, only the HIIT group displayed significant improvement in hippocampal function, as measured by paired associative learning (PAL). MRI from the HIIT group showed abrogation of the age-dependent volumetric decrease within several cortical regions including the hippocampus and improved functional connectivity between multiple neural networks not seen in the other groups... Importantly, improvement was retained for at least 5 years following initiation of HIIT, suggesting that the changes seen in hippocampal volume and connectivity underpin this long-term maintenance." (abstract, results, passage verified)
    pubmedfull study (doi)
0:07:59Tommy Woodsupportedmoderate

The adult human brain does not generate new neurons across most regions, producing only tiny numbers in areas such as the olfactory bulb and the dentate gyrus of the hippocampus.

"One of the things that I think we've gotten confused about is the fact that the adult brain does not make new neurons in many places, right? Maybe in the olfactory bulbs and the dentate gyrus of the hippocampus, but tiny, tiny number. But like compared to the rest of the brain, they're not—you're not really making new cells." (said at 0:07:59)

The speaker's statement accurately reflects the neuroscientific consensus. Across the vast majority of the adult human brain (including the neocortex), neurogenesis does not occur. Adult neurogenesis in mammals is strictly restricted to specialized neurogenic niches, primarily the subgranular zone of the hippocampal dentate gyrus and the subventricular zone (which supplies the olfactory bulb in rodents, though olfactory bulb neurogenesis in adult humans is undetectable or extremely scarce). Consequently, new neurons represent an exceedingly tiny fraction compared to the brain's overall neuronal population.

0:09:54Tommy Woodsupportedmoderate

The human brain largely finishes generating new neurons around 2 or 3 years of age, after which brain development and functional refinement primarily occur through the pruning and removal of synapses.

"The brain has kind of finished developing new neurons sometime around 2 or 3 years old, right? Beyond that point, you're actually primarily removing connections in order to refine functions based on the exposures that you have, be they language, motor, social skills, which is what the brain is essentially developing during that time period." (said at 0:09:54)

The speaker's statement accurately summarizes human neurodevelopmental dynamics. Most neuronal generation (neurogenesis) across the human brain occurs prenatally, with any remaining postnatal neurogenesis in regions like the dentate gyrus dropping sharply during the first few years of life (infancy/early childhood). Subsequent functional maturation and brain development beyond early childhood proceed predominantly through experience-dependent synaptic remodeling, including extensive synaptic pruning and elimination.

0:12:12Tommy Woodsupportedmoderate

Epidemiological and intervention studies indicate that older adults who continue engaging in cognitively demanding activities such as reading, crosswords, lectures, and volunteering experience slower cognitive decline, better maintenance of function, or lower rates of dementia.

"when you look at a combination of epidemiological studies and intervention studies in older adults, everything about maintaining cognitive function later in life, you definitely see that those who continue to engage in hobbies and activities that are cognitively engaging or cognitively demanding—and that can be lectures, that can be volunteering, that can be, you know, reading, crosswords, that kind of stuff—those individuals tend to either have slowed rates of decline or better maintenance of function over time and/or lower rates of dementia." (said at 0:12:12)

Epidemiological cohort studies and meta-analyses consistently show that participation in cognitively stimulating leisure activities (such as reading, crafts, intellectual hobbies, and social/volunteer activities) is associated with a significantly lower risk of all-cause dementia and Alzheimer's disease. Furthermore, randomized intervention trials and meta-analyses of cognitively stimulating activities demonstrate improved cognitive functioning and maintenance of function in older adults.

0:13:03Tommy Woodsupportedmoderate

Randomized controlled trials show that novel cognitive stimuli in older adults—such as language learning, coordinative movement, musical training, or musical pattern identification—lead to improvements in cognitive function, particularly executive function.

"there's an increasing body of literature that shows that by engaging older adults in novel cognitive activities, you see improvements in function. So that can be language learning. That can be complex, like coordinative movement or exercise. You see the same things with like musical training, like people learning a new musical instrument or learning musical theory, trying to identify different patterns in music. And you see in randomized controlled trials improvements particularly in executive function" (said at 0:13:03)

The speaker accurately describes published randomized controlled trials demonstrating that engaging older adults in novel cognitively demanding activities (such as musical instrument training, coordinative motor training, and novel skill acquisition) leads to cognitive enhancements, particularly in executive function domains such as working memory, processing speed, and cognitive switching.

0:19:20Tommy Woodsupportedmoderate

A secondary analysis of the ACTIVE trial showed that older adults who completed visual processing speed training with booster sessions at 1 and 3 years had a significantly reduced risk of dementia 20 years later.

"They just published a secondary analysis of the ACTIVE trial that showed that those who did processing speed training with booster sessions at one and three years had a significantly decreased risk of dementia 20 years later." (said at 0:19:20)

A 20-year follow-up secondary analysis of the ACTIVE randomized controlled trial linked trial data to Medicare claims (1999–2019) to evaluate diagnosed Alzheimer's disease and related dementias (ADRD). The study found that participants randomized to the speed of processing training arm who completed booster sessions had a statistically significant 25% reduction in the risk of diagnosed ADRD (HR 0.75, 95% CI: 0.59–0.95), whereas those without booster sessions or in the memory/reasoning arms showed no significant reduction.

0:20:29Tommy Woodsupportedmoderate

A Nature journal study analyzing data from approximately 1.2 million Implicit Association Test participants found that simple reaction time begins declining gradually in one's 30s and drops faster after 60, whereas processing speed remains relatively stable until around age 60 before declining.

"Probably the biggest one looked at data that came from the Implicit Association Test people might have heard of... published in one of the Nature journals a few years ago. And what they showed was that you can separate out reaction time versus processing speed... reaction time kind of slowly decreases on average in a population of—it was about 1.2 million people—slowly decreases in sort of like from about our 30s and then maybe decreases even more once we get past about 60. Processing speed on average tended to be more stable until about 60 years old and then tends to drop off." (said at 0:20:29)

A 2022 study published in Nature Human Behaviour analyzed cross-sectional data from over 1.18 to 1.2 million participants completing Implicit Association Test tasks. By applying a Bayesian diffusion model to decompose raw response times into distinct cognitive components (such as non-decisional processing, decision caution, and information-processing speed/drift rate), the authors found that raw response times begin slowing in early adulthood (around age 20), but this is driven by greater caution and non-decisional slowing. In contrast, mental processing speed (drift rate) remains high and relatively stable until approximately age 60 before showing a pronounced decline.

  • supports: Mental speed is high until age 60 as revealed by analysis of over a million participants. (Nature human behaviour 2022) · cited 54x in the literature
    "Here we apply a Bayesian diffusion model to extract interpretable cognitive components from raw response time data. We apply our model to cross-sectional data from 1.2 million participants to examine age differences in cognitive parameters... Our results indicate that response time slowing begins as early as age 20, but this slowing was attributable to increases in decision caution and to slower non-decisional processes, rather than to differences in mental speed. Slowing of mental speed was observed only after approximately age 60." (abstract, results, passage verified)
    pubmedfull study (doi)
0:28:55Tommy Woodsupportedmoderate

The function and stability of the frontoparietal brain network, which is critical for focus and attention, decreases with age.

"particularly the networks like the frontoparietal network that we know is really important for like focus and attention, and its function does tend to decrease with age." (said at 0:28:55)

Neuroimaging studies consistently demonstrate that large-scale brain network architecture undergoes age-related changes, with functional connectivity and system segregation within cognitive control and attentional networks—specifically the frontoparietal network—declining across the adult lifespan. These functional network alterations mediate age-related declines in executive function and attentional control.

0:07:00Tommy Woodsupportedhigh

Santiago Ramón y Cajal proposed that the adult brain is immutable and ceases development after reaching adulthood, while also suggesting that changes in neuronal connections could account for learning.

"And this goes all the way back to Cajal who said the adult brain is immutable, right? He told us that you got into adulthood, it finished developing and then it was kind of done. He then at other times also said that changes in the connections between neurons could explain learning." (said at 0:07:00)

Santiago Ramón y Cajal famously articulated both views during his career. In his 1928 work 'Degeneration and Regeneration of the Nervous System', he asserted that once neurodevelopment concludes, central nervous pathways are 'fixed, ended, and immutable' and that 'everything must die, nothing may be regenerated.' Concurrently, in his earlier and broader theoretical writings on the neuron doctrine and brain plasticity, Cajal hypothesized that mental exercise and learning could strengthen or modify the connections and terminal arborizations between neurons.

0:18:04Tommy Woodsupportedhigh

The FINGER trial in Finland and its US replication, the POINTER trial, evaluated multidomain lifestyle interventions comprising diet, exercise, cardiovascular risk factor monitoring and treatment, and cognitive brain training in older adults.

"There was something similar done in the POINTER trial, which was in older adults, now 60s and 70s, that was done here in the US, that was a replication of an older trial called the FINGER trial that was done in Finland. But what those guys did was something very similar. So it's diet, exercise, monitoring and treating cardiovascular risk factors, and then brain training." (said at 0:18:04)

The speaker's claim accurately describes both the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) and its US replication study (U.S. POINTER). The FINGER randomized controlled trial evaluated a 2-year multidomain intervention encompassing nutritional guidance, physical exercise, cognitive training, and vascular risk monitoring in older adults aged 60-77 years. The U.S. POINTER trial was directly modeled on FINGER to test multidomain lifestyle interventions (exercise, diet, cognitive stimulation, and cardiovascular health monitoring) among at-risk older adults in the United States.

0:42:05Andrew Huberman (host)supportedvery low

Neurosurgical stimulation of the anterior midcingulate cortex in experiments by Josef Parvizi causes patients to experience a sense of impending challenge and the urge to persevere.

"this area of the brain that seems associated with tenacity, which when stimulated, people feel like an impending challenge. There's actually neurosurgery experiments done by Josef Parvizi at Stanford. People feel like, 'Oh, there's an impending challenge. I'm going to lean into it.'" (said at 0:42:05)

In a 2013 study by Josef Parvizi and colleagues at Stanford published in Neuron, intracranial electrical stimulation of the anterior midcingulate cortex (aMCC) in two patients undergoing invasive epilepsy monitoring caused autonomic arousal alongside the subjective feeling of an impending challenge and the determined resolve ('will to persevere') to push through or overcome it. Because this evidence comes from an intracranial stimulation case study in two patients, the GRADE certainty is very low.

0:48:53Tommy Woodsupportedlow

In a study comparing young and older expert and amateur pianists on piano-specific motor tasks, the primary predictor of performance was amount of practice rather than age.

"so I'm thinking about one specific study that was done in pianists. So this was kind of related to the Ericsson studies in violinists, right? But this time they were looking at pianists. And so they had four groups: older and younger—so the younger was like 20s and 30s, older were 50s and 60s—expert and amateur pianists... And what they found was that the most important predictor of how well somebody performed at those piano-specific skills was not their age; it was how much they practice." (said at 0:48:53)

The speaker accurately describes the classic 1996 study by Ralf Krampe and K. Anders Ericsson (J Exp Psychol Gen, PMID 8945787). The researchers evaluated young and older expert and amateur pianists and found that while general processing speed showed expected age-related decline across groups, performance on domain-specific pianistic tasks was maintained in older experts, with the level of skill retention predicted by the amount of deliberate practice rather than age.

0:52:34Tommy Woodsupportedmoderate

The study by Anders Ericsson found that 10,000 hours was the average practice time accumulated by expert violinists by age 20, rather than an absolute threshold for achieving expertise.

"what the study showed was that 10,000 hours was the average amount of time that an expert violinist had spent practicing by the time they reached 20 years old. That's what the study showed. They weren't even experts by that point. That was how much they'd practiced, you know, essentially in their youth." (said at 0:52:34)

The speaker accurately describes the findings and context of the seminal study by K. Anders Ericsson, Ralf Krampe, and Clemens Tesch-Römer (1993). In the study, the top group of student violinists (the 'best' students destined for international soloist careers) had accumulated an estimated average of approximately 10,000 hours of solitary deliberate practice by age 20 (compared to ~7,500 hours for 'good' students and ~4,000 hours for music education students). Ericsson frequently clarified that 10,000 hours was an average estimate among developing 20-year-old conservatory students rather than a strict, universal threshold or magical rule for becoming an expert.

0:53:12Tommy Woodsupportedlow

In Anders Ericsson's research on expert violinists, the musicians typically practiced for about two sessions of 60 to 90 minutes per day.

"Other parts of that study kind of looked at the practice routines of these expert violinists, and what they found was that they tended to practice for about two sessions of 60 to 90 minutes a day." (said at 0:53:12)

The speaker accurately describes the findings of Anders Ericsson and colleagues' seminal 1993 study on deliberate practice in violinists (Ericsson, Krampe, & Tesch-Römer, 1993, Psychol. Rev.). In that study, diary analyses of elite student violinists at the Music Academy of West Berlin showed that deliberate practice was typically broken into focused sessions lasting approximately 60 to 90 minutes (often about two to three sessions daily, totaling around 3.5 to 4 hours per day), accompanied by afternoon rest or naps to sustain concentration.

0:51:28Andrew Huberman (host)supportedmoderate

Omega-3 fatty acids and coenzyme Q10 support cardiovascular health, cellular health, energy production, and brain health.

"Omega-3 and co-enzyme Q10 are known to support cardiovascular health, cellular health, and energy generally, brain health, and much more." (said at 0:51:28)

Omega-3 fatty acids (EPA and DHA) and coenzyme Q10 (ubiquinone) have well-established physiological roles in cardiovascular, cellular, energetic, and neurological function. CoQ10 is a key electron carrier in mitochondrial ATP synthesis necessary for high-energy organs such as the heart and brain, while omega-3 polyunsaturated fatty acids regulate membrane structure, lipid metabolism, mitochondrial function, cardiovascular endpoints, and neuroprotection.

0:30:25Tommy Woodsupportedhigh

Tommy Wood and Josh Turknett published a scientific paper proposing that age-related cognitive decline is partly driven by a decrease in novel and complex cognitive inputs needed to stimulate neuroplasticity.

"So a few years ago, I wrote a paper with my colleague Josh Turknett about this idea that potentially one of the reasons why we lose cognitive function as we get older is because we stop giving our brain novel inputs or complex inputs that help maintain function, drive neuroplasticity." (said at 0:30:25)

Tommy Wood and Josh Turknett (along with Michael A. Kelly) published a 2022 review article titled 'Demand Coupling Drives Neurodegeneration: A Model of Age-Related Cognitive Decline and Dementia' in Cells (PMID 36139364). The paper proposes the demand-coupling hypothesis, arguing that a reduction in cognitive demand and stimulus over the lifespan downregulates neuroplastic, growth, and repair processes, contributing to structural and functional brain deterioration.

0:39:01Tommy Woodsupportedmoderate

Sports psychology literature identifies clutch states alongside flow states as high-performance states, characterized by peak performance achieved through deliberate effort, intense focus, and high arousal under pressure rather than effortless execution.

"If you think about this in terms of sports performance, there might be broadly two states associated with top-level performance. One is flow states, the other is clutch states. And so in a clutch state, you are still at the optimal level of arousal, right? If we think about the arousal curve and performance, which we can come back to. But so, at the optimal level of arousal, which is required for you to perform the skill that you're trying to perform, but when you're in a clutch state, it still feels like hard work, right?" (said at 0:39:01)

Sports psychology research, led notably by Swann and colleagues, identifies clutch states alongside flow states as distinct psychological states underlying optimal sports performance. Whereas flow is characterized by effortless attention and automaticity, clutch states occur in high-pressure contexts and are defined by deliberate concentration, intense effort, heightened awareness, and optimal arousal where performance feels like hard work.

1:01:17Tommy Woodsupportedmoderate

The SMILES trial was the first randomized controlled trial in depression that demonstrated significant improvements in mood symptoms from a dietary intervention.

"And so this is very similar to the diet they used in the SMILES trial, which was the first randomized controlled trial in depression that showed significant improvements in mood symptoms." (said at 1:01:17)

The SMILES trial (Jacka et al., 2017) was a 12-week single-blind randomized controlled trial (n=67) investigating an adjunctive dietary intervention (modified Mediterranean diet) versus a social support control in adults with moderate to severe major depression. The dietary intervention led to statistically significant and clinically meaningful improvements in depression severity measured by the Montgomery-Åsberg Depression Rating Scale (MADRS) (Cohen's d = -1.16, p < 0.001) and higher remission rates (32.3% vs 8.0%), establishing it as the first RCT testing dietary modification for the treatment of clinical major depression.

1:01:38Tommy Woodsupportedhigh

A randomized controlled trial published in the New England Journal of Medicine comparing the MIND diet to standard caloric restriction found similar cognitive benefits in both groups.

"There was actually a big trial of the MIND diet. It was published in the New England Journal of Medicine a couple of years ago, and they compared the MIND diet to standard caloric restriction. And actually they saw similar benefits in both groups." (said at 1:01:38)

A 3-year randomized controlled trial published in the New England Journal of Medicine (2023) evaluated 604 older adults without cognitive impairment, comparing the MIND diet with mild caloric restriction against a control diet with mild caloric restriction. Both groups experienced small, similar improvements in global cognitive performance from baseline to year 3 (an increase of 0.205 standardized units in the MIND-diet group vs. 0.170 in the control group; mean difference 0.035, p = 0.23), with no statistically significant difference between the groups.

1:02:04Tommy Woodsupportedlow

A UK Biobank study found that removing individual foods or food groups from the Mediterranean diet did not alter the relationship between Mediterranean diet adherence and reduced dementia risk.

"so a big one that came out of the UK Biobank was that they took out individual foods or food components of the Mediterranean diet to see if that changed the relationship between the Mediterranean diet and dementia risk. And there was no food or olive oil or food group or eating more or less meat that changed the relationship between the Mediterranean diet and dementia risk." (said at 1:02:04)

A prospective cohort study of 60,298 UK Biobank participants followed for 9.1 years (Shannon et al., BMC Medicine 2023, PMID: 36915130) evaluated adherence to the Mediterranean diet (using MEDAS and Pyramid scores) and all-cause dementia risk. Higher Mediterranean diet adherence was associated with significantly reduced dementia risk (HR 0.77, 95% CI 0.65–0.91). In the study's sensitivity analyses, removing individual components and food groups from the diet scores one at a time did not alter the overall protective association. Certainty is low due to the observational cohort design.

1:03:14Tommy Woodsupportedmoderate

Studies comparing Bolivian Tsimane, Moseten, and industrialized Western populations showed a bell-shaped curve relationship between energy availability and brain volume.

"There was one group that looked at different tribes in Bolivia: the Bolivian Tsimané, who are a hunter-gatherer group; the Mosetén, who are kind of an intermediate group between sort of the Tsimané and like a standard kind of industrialized group; and then industrialized humans in the US and Europe. And what they found is there's kind of this bell-shaped curve between energy availability and brain volume." (said at 1:03:14)

A 2023 study published in PNAS by Irimia et al. evaluated brain volume across the Bolivian Tsimane (forager-horticulturalists), the Moseten (a more acculturated, transitional farming group), and industrialized populations in the US and Europe. The authors tested an evolutionary framework called the 'embarrassment of riches' (EOR) model and found a non-linear, inverted U-shaped (curvilinear/bell-shaped) relationship between energy availability markers (such as body mass index and non-HDL cholesterol) and brain volume across these populations: brain volume was positively associated with energy availability up to moderately high levels, but declined at the highest levels seen in industrialized, sedentary contexts.

1:06:28Tommy Woodsupportedlow

Studies show that individuals with lower dietary magnesium intakes tend on average to perform less well on cognitive function tests.

"So, there are some studies that show that those who have lower magnesium intakes tend on average to perform less well on some cognitive function tests." (said at 1:06:28)

The speaker's statement is framed carefully ('there are some studies that show...') and is accurate. Observational studies, including analyses of the National Health and Nutrition Examination Survey (NHANES), report that individuals with lower dietary magnesium intake or higher magnesium depletion scores perform significantly worse on specific cognitive function tests, including the Digit Symbol Substitution Test and Animal Fluency Test. Because this evidence comes primarily from cross-sectional and observational cohort designs, the GRADE certainty is low.

1:11:09Tommy Woodsupportedvery low

In single-dose rodent studies, more omega-3 fatty acids enter the brain in the phospholipid form compared to the triglyceride form.

"When you compare a single dose of phospholipid versus triglyceride form, then more of the phospholipid form gets into the brain. Most of this comes from rodent studies" (said at 1:11:09)

Acute single-dose pharmacokinetic and tracer studies in rodents demonstrate that omega-3 fatty acids (specifically DHA) administered in phospholipid forms (such as phosphatidylcholine or phosphatidylserine) achieve substantially higher brain uptake and cortical accumulation compared to the triglyceride form. Because this specific comparative claim relies on animal tracer studies, the GRADE certainty is very low.

1:12:19Tommy Woodsupportedhigh

A trial out of USC demonstrated that omega-3 supplementation increased omega-3 levels in cerebrospinal fluid but did not produce changes in cognitive function or brain MRI structure.

"There was actually a very recent one that just came out of USC where they gave omega-3s for a long period of time. They measured omega-3 levels in the CSF, right, in the spinal fluid of these people to show that the omega-3s were getting into the brain. They didn't see any changes in terms of cognitive function or brain structure on an MRI scan." (said at 1:12:19)

The statement is fully supported by the PreventE4 randomized, double-blind, placebo-controlled trial conducted at the University of Southern California (USC). In 365 non-demented older adults at risk for dementia who were randomized to 2 g/day DHA or placebo for 24 months, DHA supplementation achieved central nervous system target engagement by significantly increasing the DHA/AA ratio in cerebrospinal fluid (CSF) at 6 months, but produced no significant differences in cognitive performance or brain MRI volumetric measures over 24 months.

1:13:16Tommy Woodsupportedmoderate

Elevated blood homocysteine increases risk for cognitive decline and dementia at levels above 13 micromol/L, with elevated risk likely starting above 10 to 11 micromol/L.

"A normal range for homocysteine, which goes up if you need some of these methylation-dependent B vitamins, the normal range might go up to like 15 or 16. But we know that risk is definitely elevated above 13 and is probably elevated above sort of 10 to 11." (said at 1:13:16)

The speaker's claim is supported by international consensus and cohort evidence. An international consensus statement on homocysteine and dementia established that elevated total homocysteine (tHcy) is a modifiable risk factor for cognitive decline, Alzheimer's disease, and dementia, noting that risk increases at moderately raised concentrations (>11 μmol/L), which fall well within traditional laboratory 'normal' ranges (often up to 15 μmol/L). Multiple cohort studies and clinical trials have similarly established elevated risks and intervention benefits around thresholds of 11 to 13–14 μmol/L.

1:14:03Tommy Woodsupportedmoderate

The VITACOG trial and B-PROOF trial demonstrated that lowering elevated homocysteine with B vitamins does not improve cognition or slow cognitive decline unless baseline omega-3 levels are adequate.

"So, if you give B vitamins to somebody who has elevated homocysteine, you bring down their homocysteine, but they have poor omega-3 levels, you don't see any benefit. And that's been shown in two trials. It was originally shown in the VITACOG trial that was run out of the University of Oxford. It was then replicated in the B-PROOF trial." (said at 1:14:03)

The speaker accurately summarizes the findings from the VITACOG trial and the subsequent post-hoc analysis of the B-PROOF trial. In both trials, B-vitamin supplementation (which lowers elevated homocysteine) slowed cognitive decline and brain atrophy in individuals with high or adequate baseline omega-3 (particularly DHA) concentrations, whereas participants with low omega-3 status did not experience cognitive benefit. The certainty is rated moderate because these findings stem from post-hoc interaction analyses of randomized controlled trials rather than primary pre-specified endpoints.

1:14:23Tommy Woodsupportedmoderate

The OmegAD trial demonstrated that omega-3 supplementation did not result in cognitive benefit if participants had elevated homocysteine levels.

"Then the other side has also been shown: in the OmegAD trial, they showed that supplements with omega-3s didn't result in any benefit if people had elevated homocysteine." (said at 1:14:23)

A post hoc analysis of the OmegAD randomized clinical trial (PMID 30958356) evaluated whether baseline plasma total homocysteine (tHcy) levels modified the cognitive effects of omega-3 fatty acid supplementation in 171 patients with mild to moderate Alzheimer's disease. The authors found a significant interaction between omega-3 treatment and baseline tHcy on MMSE and CDR-sob scores: omega-3 supplementation significantly improved cognition and clinical status only in patients with low tHcy (<11.7 μmol/L), showing no benefit in those with higher/elevated homocysteine levels. The certainty is graded as moderate because this was a post hoc subgroup analysis of an RCT.

1:15:30Tommy Woodsupportedhigh

In the COSMOS trial, older adults given a standard daily multivitamin (Centrum Silver) showed improvements in cognitive function.

"Potentially the one recent example of kind of just giving a broad-based kind of set of nutrients with a multivitamin that seemed to work fairly well was the COSMOS study people may have heard of. It was thousands of people, of older adults, um, and they were given either a multivitamin or a a flavonoid supplement... Yeah, it was it was Centrum Silver, right? The most basic multivitamin... And in that study, those who got the mil- got the multivitamin saw, you know, changes in cognitive function that suggested some like some some improvements." (said at 1:15:30)

The speaker's statement accurately summarizes findings from the COcoa Supplement and Multivitamin Outcomes Study (COSMOS). In COSMOS-Mind (a 2x2 factorial randomized clinical trial in 2,262 older adults) and subsequent cognitive substudies, daily multivitamin-mineral supplementation (using Centrum Silver) resulted in statistically significant benefits in global cognition and episodic memory compared with placebo.

1:17:01Tommy Woodsupportedmoderate

In the COSMOS trial, cocoa flavanol supplementation improved cognitive outcomes only in individuals who had poor diet quality at baseline.

"But what they also showed was that um supplementing with this antioxidant cocoa flavanol was only beneficial in those who tended to have a poor quality diet to start with." (said at 1:17:01)

In the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) cognitive substudies (COSMOS-Web and COSMOS-Clinic), daily cocoa extract/flavanol supplementation did not show statistically significant overall cognitive benefits in the full cohort, but analyses showed memory and cognitive improvements specifically among participants with lower baseline diet quality or lower habitual flavanol consumption.

1:18:45Andrew Huberman (host)supportedhigh

Most growth hormone secretagogues carry a risk of insulin resistance and diabetes, particularly at higher doses.

"and with with the most of those growth hormone secretagogues come with a risk of insulin resistance, diabetes at high you particularly at higher doses." (said at 1:18:45)

Randomized controlled clinical trials evaluating growth hormone secretagogues (such as the oral ghrelin receptor agonist MK-677/ibutamoren) demonstrate that increasing growth hormone secretion leads to dose-related reductions in insulin sensitivity and elevations in fasting blood glucose levels, impairing glucose homeostasis.

1:00:17Tommy Woodsupportedmoderate

The MIND diet was developed from data in the Rush Memory and Aging Project, where higher MIND diet scores were associated with a lower risk of later dementia.

"There's the MIND diet, Mediterranean-DASH Intervention for Neurodegenerative Delay. It came out of the Rush Memory and Aging Project, and it's basically just a version of the Mediterranean diet kind of focused on dementia prevention. And the way they initially created it was they looked at foods that people ate more or less of and created a score, and those who had a higher score had a lower risk of later dementia." (said at 1:00:17)

The MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet was developed by Martha Clare Morris and colleagues at Rush University using dietary and cognitive data from the Rush Memory and Aging Project (MAP). In their original prospective cohort analyses, higher MIND diet scores were significantly associated with both slower rates of cognitive decline and a substantially lower risk of incident Alzheimer's dementia.

1:06:00Tommy Woodsupportedhigh

Astaxanthin is the carotenoid responsible for the pink color of shrimp and salmon.

"the carotenoids that make things orange, yellow, and red—lutein, zeaxanthin, astaxanthin, if it comes from seafood, that's what makes shrimp and salmon pink." (said at 1:06:00)

Astaxanthin is well-established as the primary keto-carotenoid pigment responsible for the characteristic pink-to-red pigmentation in salmonid flesh and crustacean exoskeletons (such as shrimp). Marine organisms accumulate astaxanthin through their diet or biosynthesize it from related carotenoid precursors, giving these seafoods their distinctive coloration.

1:29:20Tommy Woodsupportedhigh

There is a lack of good quality human clinical evidence demonstrating the efficacy of BPC-157 for injury repair.

"BPC-157, people are taking it without even knowing what the desired effect is, [1:29:25] HOST: recovery is really broad. I think it's [1:29:26] GUEST1: injury repair, that's the thesis. No human evidence as far as no good human evidence." (said at 1:29:20)

The speaker's statement is supported. Systematic and narrative reviews evaluating BPC-157 for musculoskeletal injury repair and sports medicine confirm that almost all published evidence is preclinical (animal and in vitro models). To date, rigorous, high-quality human clinical trials evaluating its efficacy for tissue or injury repair are absent; only uncontrolled pilot case series or retrospective reports of very low methodological quality exist.

1:31:21Andrew Huberman (host)supportedmoderate

High doses of creatine can be administered to frail, older individuals with essentially no side effects.

"At least we know that you can give high doses of creatine to frail old older individuals with essentially no side effects, right?" (said at 1:31:21)

Extensive literature and systematic reviews evaluating creatine monohydrate supplementation across older adults and various clinical populations confirm an excellent safety profile with essentially no serious adverse effects. High loading doses (e.g., 20 g/day or ~0.3 g/kg/day) and long-term maintenance doses do not impair renal or hepatic function in older adults. Minor gastrointestinal discomfort or transient water retention are occasionally reported with large single boluses, but these are generally mild. While clinical trials specifically isolating 'frail' older adults are fewer in number compared to general older cohorts, available evidence consistently indicates that creatine is safe and well-tolerated in aging populations.

1:33:54Tommy Woodsupportedmoderate

An athlete's subjective feeling is a better predictor of athletic performance than heart rate variability (HRV) or blood tests.

"And we know that how you feel, so how an athlete feels is a much better predictor of their performance than their HRV or any of their blood test." (said at 1:33:54)

A landmark systematic review of 56 studies by Saw et al. (2016, PMID: 26423706) evaluated subjective self-reported measures (e.g., mood, perceived stress, well-being) alongside objective physiological and biochemical measures (e.g., resting heart rate/HRV, blood biomarkers, oxygen consumption) to monitor athlete training load responses. The authors found that subjective measures responded to acute and chronic training loads with significantly greater sensitivity and consistency than objective measures such as resting blood tests or heart rate metrics. While both subjective and objective markers are commonly used to assess fatigue and readiness to perform, subjective well-being consistently demonstrates superior responsiveness to training stress compared to blood tests or resting cardiac metrics.

1:35:29Tommy Woodsupportedmoderate

Caffeine administration can make individuals feel they are performing better on complex cognitive tasks like the N-back task while they are actually performing worse.

"So there there are studies that show that um uh giving people caffeine makes them [snorts] feel like they're performing better, but they're actually performing worse on certain cognitive tasks. So there's been studies done with like the the N-back task." (said at 1:35:29)

Randomized, double-blind, placebo-controlled trials have demonstrated that caffeine administration can impair working memory performance and increase error rates on demanding cognitive tasks, specifically the N-back task (such as the 3-back task), despite caffeine's well-known subjective effects on alertness and perceived cognitive enhancement.

1:36:04Andrew Huberman (host)supportedmoderate

A study published in Science found that ADHD stimulant medications like methylphenidate given to healthy non-ADHD individuals caused a dissociation where participants felt they performed better despite not objectively improving.

"So there was a paper that came out in Science a couple of years ago with uh giving people um methylphenidate, some of the or some of the other like ADHD medications in people who don't have ADHD. These stimulant medications again show this dissociation between so they feel great." (said at 1:36:04)

A 2023 double-blind, randomized, placebo-controlled crossover study published in Science Advances (PMID: 37315143) investigated the effects of methylphenidate, dextroamphetamine, and modafinil on complex problem-solving (the knapsack task) in healthy non-ADHD participants. The authors found that stimulant medications increased motivation and effort (time spent and steps taken), but significantly decreased the quality/productivity of that effort and diminished task performance relative to placebo, creating a clear dissociation between increased motivation/effort and objective performance outcome.

1:36:30Tommy Woodsupportedmoderate

Studies objectively evaluating creativity show that individuals using cannabis perceive themselves as more creative, but objective ratings show no increase in creativity.

"And that's again been like formalized in studies where where you can do these tests where then other people objectively see how creative were you. People taking cannabis felt like they were more creative, but actually they weren't." (said at 1:36:30)

Experimental studies assessing the acute effects of cannabis on creativity demonstrate that cannabis use leads participants to evaluate their own ideas (and others' ideas) as more creative, but objective ratings and standardized creativity tests show no actual increase in creative output or divergent thinking (with higher doses even impairing divergent thinking).

1:37:25Tommy Woodsupportedhigh

In meta-analyses of acute exercise and immediate post-exercise cognitive function, a 20- to 30-minute jog has the strongest supporting evidence.

"I think that when you look at meta-analyses of exercise and then cognitive function immediately afterwards, the protocol that has like the best evidence for it is like a 20- to 30-minute jog, right?" (said at 1:37:25)

Meta-analyses evaluating the acute effects of a single bout of exercise on immediate post-exercise cognitive performance (such as Chang et al., 2012, Lambourne & Tomporowski, 2010, and subsequent meta-reviews) consistently show that moderate-intensity aerobic exercise (such as a 20- to 30-minute jog or cycle) produces the most reliable improvements in cognitive function immediately following the session. Moderator analyses in these meta-analyses demonstrate that exercise duration (optimally around 20 minutes or 20–30 minutes) and moderate intensity yield the largest and most consistent cognitive benefits.

1:39:10Tommy Woodsupportedmoderate

In older adults, brisk walking for 40 minutes three times per week for one year led to significant increases in hippocampal volume, VO2 max, circulating BDNF, and memory performance.

"So most people who listen to your show are probably familiar with a study where in older adults, they had them do brisk walking three times a week, 40 minutes... And they saw significant increases in the volume of the hippocampus, increases in VO2 max fitness, increases in circulating BDNF levels—though circulating BDNF doesn't actually get into the brain, but it's kind of telling you something about probably BDNF that's being produced in the brain—and improvements in memory." (said at 1:39:10)

The speaker accurately describes the findings of the landmark 2011 randomized controlled trial by Erickson et al. (PMID 21282661). In the study, 120 sedentary older adults were randomized to either moderate-intensity walking (progressing to 40 minutes per day, 3 days per week for 1 year) or a stretching control group. The aerobic exercise group showed a 2% increase in anterior hippocampal volume (reversing age-related decline), increased aerobic fitness, improvements in spatial memory, and an association between increased hippocampal volume and serum BDNF levels.

1:41:15Tommy Woodsupportedmoderate

Lactate produced during high-intensity exercise readily crosses into the brain and stimulates brain-derived neurotrophic factor (BDNF) production.

"We know that lactate very easily gets into the brain, stimulates BDNF production as kind of part of that support of neuroplasticity or augmenting recent neuroplastic processes." (said at 1:41:15)

The claim accurately reflects established mechanistic and experimental findings. Peripherally generated lactate (such as during exercise) crosses the blood-brain barrier via monocarboxylate transporters (MCTs). Landmark rodent studies (e.g., El Hayek et al., 2019) demonstrated that exercise-derived lactate crosses the blood-brain barrier to trigger hippocampal Bdnf expression and TrkB signaling via a SIRT1-dependent pathway, enhancing learning and synaptic plasticity. Complementary human experiments show that exogenous lactate infusion increases circulating BDNF levels even in the absence of exercise.

1:41:34Andrew Huberman (host)supportedmoderate

A 2020 study by the Environmental Working Group estimated that over 200 million Americans are exposed to PFAS forever chemicals via drinking tap water.

"In fact, a 2020 study by the Environmental Working Group estimated that more than 200 million Americans are exposed to PFAS chemicals, also known as forever chemicals, through drinking of tap water." (said at 1:41:34)

A 2020 study conducted by scientists at the Environmental Working Group (Andrews & Naidenko, published in Environmental Science & Technology Letters) analyzed publicly available drinking water data sets across the United States. They estimated that over 200 million Americans likely receive tap water contaminated with perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) at or above 1 ng/L.

1:42:00Andrew Huberman (host)supportedmoderate

The Environmental Working Group showed that over 122 million Americans drink tap water containing high levels of chemicals known to cause cancer.

"The Environmental Working Group has also shown that over 122 million Americans drink tap water with high levels of chemicals known to cause cancer." (said at 1:42:00)

A 2019 study published by researchers at the Environmental Working Group (Evans et al., Heliyon) evaluated 22 carcinogenic contaminants across 43,598 public water systems serving nearly 280 million Americans. The authors modeled cumulative lifetime cancer risk from drinking water contaminants (primarily arsenic, disinfection byproducts, and radioactive elements) and found that national attributable cancer risk (approximately 4 in 10,000) was two orders of magnitude higher than the standard EPA benchmark of one in a million, corresponding to over 100,000 lifetime cancer cases and tens to over a hundred million people drinking water containing chemical carcinogens exceeding health-based benchmark concentrations.

  • supports: Cumulative risk analysis of carcinogenic contaminants in United States drinking water (Heliyon 2019) · cited 73x in the literature
    "Cumulative risk analysis of contaminant occurrence in United States drinking water for the period of 2010–2017 indicates that over 100,000 lifetime cancer cases could be due to carcinogenic chemicals in tap water. The majority of this risk is due to the presence of arsenic, disinfection byproducts and radioactive contaminants. For different states within the U.S., cumulative cancer risk for drinking water contaminants ranges between 1 × 10 −4 and 1 × 10 −3 , similar to the range of cumulative cancer risks reported for air pollutants." (abstract, results, passage verified)
    openalexfull study (doi)
1:52:19Tommy Woodsupportedmoderate

Resistance training performed two to three times per week for 6 to 12 months produces significant changes in brain white matter structure and improves executive function in older adults.

"There are several studies of resistance training looking at cognitive function and brain structure over time. I say several—it's like three or four in older adults. And they typically do two or three times a week, five to six exercises, three sets of 8 to 12 reps... And what you tend to see is that if you do that for at least 6 months—so the studies go on for like 6 to 12 months—you see significant changes in the structure of the white matter of the brain, and with that, improvements in executive function." (said at 1:52:19)

The speaker accurately describes findings from randomized controlled trials examining 6- to 12-month resistance training regimens (typically twice to three times weekly) in older adults. These trials demonstrate significant reductions in cortical white matter atrophy and white matter lesion progression, along with improvements in diffusion-tensor-derived white matter integrity and enhancements in executive function and memory.

1:53:40Tommy Woodsupportedmoderate

Age-related degradation of white matter structure is one of the strongest predictors of age-related cognitive decline.

"And so you see improvements in white matter structure, which—and changes in white matter structure with age are one of the best predictors of cognitive decline with age, interestingly, like outside of other things you see in terms of neuropathology, amyloid, tau, etc." (said at 1:53:40)

Extensive neuroimaging literature demonstrates that age-related decline in cerebral white matter structural integrity (measured via diffusion tensor imaging and white matter hyperintensities) is a major mediator and independent predictor of cognitive decline in aging, particularly in domains such as processing speed, executive function, and task performance. Furthermore, white matter degradation often occurs independently of or precedes classical gray matter atrophy and neuropathological markers like amyloid-beta and tau.

1:54:20Tommy Woodsupportedmoderate

Resistance training increases IGF-1, which is critical for the development and maintenance of white matter structure in the brain across the lifespan.

"In resistance training, I think the primary mediator of that, or one of them, is IGF-1, which is particularly increased with resistance training. We know that IGF-1 is really critical to the development of white matter, you know, right in the womb and then as a baby, and it seems to be also really important for white matter structure throughout the lifespan." (said at 1:54:20)

The evidence supports the speaker's claim. Resistance training consistently stimulates the production of insulin-like growth factor 1 (IGF-1) and has been shown in clinical trials to improve cerebral white matter volume, connectivity, and oligodendrocyte function. Preclinical and developmental biology studies establish that IGF-1 is a key neurotrophic factor driving embryonic and neonatal oligodendrocyte differentiation and myelinogenesis, while continuing to regulate oligodendrogenesis, myelin plasticity, and white matter maintenance throughout adulthood and aging.

1:59:00Andrew Huberman (host)supportedhigh

Neuroscientists Jeff Lichtman and Joshua Sanes published a review paper concluding that across the published literature, nearly any molecule applied to neurons during a long-term potentiation (LTP) protocol appeared to enhance LTP.

"there was a review published by a guy named Jeff Lichtman and Josh Sanes, who were in a different field. So they did a kind of cocky thing, but back then they were like—like they're good guys. I know them both. But they published this review about long-term potentiation where they said they did a review of the literature, and they said basically you can throw any molecule on a couple of neurons and do the protocol for long-term potentiation, and you get an enhancement of long-term potentiation." (said at 1:59:00)

Joshua Sanes and Jeff Lichtman published a prominent 1999 review in Nature Neuroscience titled 'Can molecules explain long-term potentiation?' (PMID 10404178). In this review, outsider neuroscientists Sanes and Lichtman critically analyzed the vast literature on long-term potentiation (LTP), cataloging over one hundred candidate molecules that had been reported to block, facilitate, or induce LTP when manipulated, arguing that the literature had implicated nearly every tested molecule without establishing a cohesive or specific molecular pathway.

2:03:04Tommy Woodsupportedhigh

Alzheimer's disease accounts for approximately 60% to 80% of all dementia cases.

"Alzheimer's disease is the most common. It makes up about 60 to 80% of cases of dementia." (said at 2:03:04)

Epidemiological literature consistently identifies Alzheimer's disease as the most common form of dementia, accounting for an estimated 60% to 80% of all dementia cases worldwide.

2:04:15Tommy Woodsupportedhigh

Monogenic dominant mutations in PSEN1, PSEN2, or APP account for less than 5%, and possibly as little as 1%, of Alzheimer's disease cases.

"monogenic dominant mutations that you have in—most of them happen either in the presenilin genes, PSEN1 and 2, or the amyloid precursor protein gene. They make up, at this point, less than 5%, maybe as little as 1% of Alzheimer's disease." (said at 2:04:15)

The speaker accurately states the genetic landscape of Alzheimer's disease. Monogenic, autosomal dominant forms of Alzheimer's disease (ADAD) are caused by pathogenic variants in PSEN1, PSEN2, or APP. Epidemiological and genetic studies consistently establish that these fully penetrant monogenic mutations account for a very small minority of all Alzheimer's disease cases (typically cited as <1% to at most <5% of total AD cases, representing a fraction of early-onset Alzheimer's disease).

2:05:10Tommy Woodsupportedhigh

The Lancet Commission on dementia prevention identified 14 modifiable risk factors that together account for approximately 45% of dementia cases.

"the best accepted review of all of this is run by the Lancet Commission on Dementia Prevention, overseen by Professor Gill Livingston, and their most the most recent version of this suggested there were 14 risk factors who between them accounted for about 45% of dementia risk or dementia cases, and that are modifiable." (said at 2:05:10)

The 2024 report of the Lancet standing Commission on dementia prevention, intervention, and care (led by Prof. Gill Livingston, PMID: 39096926) updated its life-course model by adding two new risk factors (untreated vision loss and high LDL cholesterol) to the previously identified 12, totaling 14 modifiable risk factors. Together, these 14 factors account for a global population attributable fraction (PAF) of approximately 45% of dementia cases.

2:08:06Tommy Woodsupportedlow

Consistently sleeping fewer than 6 hours per night is associated with an increased risk of dementia.

"when you look at the data on sleep loss and dementia risk, the cutoff is really around 6 hours. So if you're consistently sleeping fewer than 6 hours, that's where risk starts to increase." (said at 2:08:06)

Large prospective cohort evidence supports the claim that persistent short sleep duration (defined as 6 hours or fewer per night) in midlife is associated with an increased risk of developing dementia. In the Whitehall II cohort study (n=7,959 followed for 25 years), individuals who persistently slept 6 hours or fewer per night at ages 50, 60, and 70 had a 30% increased risk of incident dementia compared to those with a normal 7-hour sleep duration, independent of cardiometabolic and mental health covariates. Broader umbrella reviews also identify a U-shaped association between sleep duration and cognitive decline, although GRADE certainty is low given the observational nature of the evidence and potential for residual confounding or reverse causation.

2:10:20Tommy Woodsupportedmoderate

Natural experiments in Wales, Australia, and Canada found that eligibility for or receipt of the live attenuated shingles vaccine was associated with a decreased risk of dementia.

"The studies that have happened so far, there was one in the UK, in Wales, one in Australia, and one in Canada. And in each of those countries, what happened was that on a single date, a huge tranche of people became eligible to get the shingles vaccine... And so what they essentially consistently showed across all those different populations was that those who got the shingles vaccine or were eligible to have the shingles vaccine, depending on whether they had access to the data on whether people got it or not, had a decreased risk of dementia." (said at 2:10:20)

Large quasi-experimental studies exploiting natural experiments (regression discontinuity designs based on sharp date-of-birth eligibility cutoffs for live-attenuated herpes zoster vaccination) in Wales, Australia, and Canada consistently found that eligibility for and receipt of the shingles vaccine was associated with a significant reduction in incident dementia diagnoses.

2:11:00Tommy Woodsupportedmoderate

A US study found that the recombinant shingles vaccine Shingrix was associated with a lower risk of dementia compared to Zostavax.

"There's now a newer version called Shingrix, which is a recombinant vaccine, and there was a study done in the US that compared people who switched from—you know, there was a similar switch from Zostavax to Shingrix—and saw that Shingrix was associated with with a lower risk of dementia compared to Zostavax" (said at 2:11:00)

A large study published in Nature Medicine in 2024 evaluated electronic health records from the United States following the rapid clinical transition from the live-attenuated zoster vaccine (Zostavax) to the recombinant zoster vaccine (Shingrix). The researchers found that receipt of the recombinant vaccine was associated with a significantly lower risk of dementia over the following 6 years compared to receipt of the live vaccine, including a 17% increase in dementia diagnosis-free time (or 164 additional days lived without a diagnosis).

  • supports: The recombinant shingles vaccine is associated with lower risk of dementia. (Nature medicine 2024) · cited 130x in the literature
    "Here we used a natural experiment opportunity created by the rapid transition from the use of live to the use of recombinant vaccines to compare the risk of dementia between vaccine types. We show that the recombinant vaccine is associated with a significantly lower risk of dementia in the 6 years post-vaccination. Specifically, receiving the recombinant vaccine is associated with a 17% increase in diagnosis-free time, translating into 164 additional days lived without a diagnosis of dementia in those subsequently affected." (abstract, results, passage verified)
    pubmedfull study (doi)
2:12:45Tommy Woodsupportedmoderate

The Adult Changes in Thought study and Rush Memory and Aging Project showed that longitudinal cognitive decline occurs in step-like decreases following significant acute illness or hospitalization.

"There have been several studies. One was the Adult Changes in Thought study done at the University of Washington in Seattle primarily. A similar thing was shown in the Rush Memory and Aging Project. But basically, when you look at the same individual over time and you measure their cognitive function every few years... cognitive function doesn't just decline sort of linearly or steadily with age. It goes down, you know, a little bit on average, but the biggest decreases sort of happen stepwise after periods of significant illness. And so like in the Adult Changes in Thought study, those who'd been, you know, sick in between... had a step change down, and those who were hospitalized, that step change down was even bigger." (said at 2:12:45)

Prospective longitudinal cohort studies, including the Rush Memory and Aging Project and the Adult Changes in Thought (ACT) study, demonstrate that cognitive decline in older adults does not merely follow a smooth, steady trajectory with age, but accelerates markedly following acute, nonelective hospitalizations and severe illnesses.

2:15:30Tommy Woodsupportedhigh

Clinical studies of therapeutic hypothermia after traumatic brain injury have generally not shown a significant beneficial effect.

"there have been lots of studies where they've done cooling hypothermia in people after traumatic brain injuries and concussions; hasn't really shown much of an effect." (said at 2:15:30)

Numerous randomized controlled trials and systematic reviews/meta-analyses have evaluated therapeutic hypothermia in patients with traumatic brain injury (TBI). High-quality evidence consistently demonstrates that therapeutic hypothermia does not significantly improve mortality or long-term functional neurological outcomes compared to normothermia, and it is associated with increased risks of adverse events such as pneumonia and cardiac arrhythmias.

2:17:56Tommy Woodsupportedhigh

A clinical trial in pediatric patients with traumatic brain injury administered creatine at a dose of 0.4 grams per kilogram per day.

"The best trial was actually done in a pediatric group, although very broad, it was like 1 year old to 18 years old. But they gave 0.4 grams per kilo per day." (said at 2:17:56)

The speaker accurately describes a published randomized clinical trial by Sakellaris et al. (published in 2006 and 2008). In this trial, 39 pediatric patients with traumatic brain injury aged 1 to 18 years old were administered creatine supplementation at an oral dose of 0.4 g/kg per day for 6 months.

2:18:28Tommy Woodsupportedmoderate

Recent meta-analyses show that gastrointestinal side effects from creatine supplementation are not significantly higher than placebo.

"the most recent meta-analyses show that you actually don't get—it's actually quite rare to get more GI side effects with creatine compared to placebo." (said at 2:18:28)

Meta-analytic evidence comparing oral creatine supplementation to placebo confirms that gastrointestinal adverse events do not occur at a significantly higher rate with creatine than with placebo. For instance, a systematic review and meta-analysis of randomized studies found no significant difference in gastrointestinal events between creatine monohydrate and placebo groups (risk ratio 1.09, 95% CI 0.53 to 2.24).

2:21:08Tommy Woodsupportedmoderate

Studies in collegiate American football players show that daily supplementation with a few grams of omega-3 fatty acids reduces blood neurofilament light chain accumulation across a season.

"there are now several studies in collegiate American football players where they take a couple of grams of omega-3s every day and across a season you see less accumulation of biomarkers of injury like neurofilament light that are circulating in the blood." (said at 2:21:08)

Several clinical trials and a 2024 meta-analysis in collegiate American football athletes have examined daily omega-3 fatty acid supplementation (typically 2 to 6 grams/day of DHA or DHA/EPA) over the course of a competitive season. A meta-analysis of individual participant data from 3 trials (n = 179) found that omega-3 supplementation significantly attenuated the post-season elevation of serum neurofilament light (NfL), a biomarker of axonal injury from repetitive subconcussive head impacts.

2:21:55Tommy Woodsupportedmoderate

Two clinical studies indicate that high doses of branched-chain amino acids improve sleep in patients with traumatic brain injury.

"in TBI, there are two studies that suggest improvements in sleep with high doses of branched-chain amino acids." (said at 2:21:55)

The claim accurately reflects the published literature. A randomized, double-blind, placebo-controlled pilot clinical trial in veterans with traumatic brain injury (TBI) tested high-dose branched-chain amino acid (BCAA) supplementation (30 g twice daily, for a total of 60 g/day over 21 days) and found significant improvements in subjective insomnia symptoms, sleep latency, and wake after sleep onset. Additional pilot trial and translational data in concussed/TBI patients and animal models also demonstrate dose-dependent improvements in sleep and post-concussive symptom recovery with high-dose BCAA supplementation.

2:24:15Tommy Woodsupportedmoderate

Boswellia extract has been evaluated in three clinical trials after traumatic brain injury and demonstrated benefit.

"The one that probably has the most evidence for it is Boswellia... which is Indian frankincense. But there's an extract of Boswellia that's been tested in I think three different clinical trials after TBI, showed some benefit." (said at 2:24:15)

The speaker accurately describes the clinical trial literature on Boswellia (Indian frankincense) for traumatic brain injury (TBI). Three randomized, double-blind clinical trials have evaluated Boswellia preparations in TBI patients: (1) a 2013 crossover trial (n=38) evaluating Boswellia serrata in diffuse axonal injury finding improvements in cognitive sub-scores; (2) a 2022 trial (n=80) of a standardized Boswellia serrata extract (K-Vie) showing significant improvements across multiple cognitive measures (RAVLT, DSST, TMT-B); and (3) a 2022 trial (n=100) evaluating a Boswellia and ginger mixture (Memoral) showing significant improvements in memory parameters on the auditory-visual learning test.

2:03:04Tommy Woodsupportedhigh

The vast majority of people with Alzheimer's disease also have vascular pathology or changes in brain blood vessels.

"Like the vast majority of people who have Alzheimer's disease also have some element of pathology or changes in the blood vessels in the brain, which is what you get with vascular dementia." (said at 2:03:04)

Extensive neuropathological and autopsy studies (including the National Alzheimer's Coordinating Center, Nun Study, and Honolulu-Asia Aging Study cohorts) demonstrate that the vast majority of individuals with pathologically confirmed Alzheimer's disease exhibit concurrent cerebrovascular pathology or small vessel disease. These changes commonly include cerebral amyloid angiopathy (present in 85–90% of AD cases), arteriolosclerosis, atherosclerosis, and microinfarcts.

1:51:20Tommy Woodsupportedmoderate

Most natural experiment studies examining the shingles vaccine and dementia risk found a larger risk reduction in women than in men.

"And one of the arguments for the immunomodulatory effect is because, not in all the studies, but in most of the studies, there's a slightly bigger signal in women than there is in men." (said at 1:51:20)

Natural experiment and quasi-experimental studies investigating shingles (herpes zoster) vaccination and dementia risk have consistently reported a greater risk reduction in women than in men. For example, the landmark regression discontinuity natural experiment in Wales (PMID 40175543) reported that the protective effect of live-attenuated zoster vaccination was stronger in women than in men. Similarly, a natural experiment studying the roll-out of the recombinant shingles vaccine (PMID 39053634) found that the protective association was present in both sexes but greater in women.

1:56:40Tommy Woodsupportedmoderate

Elevations in blood sugar following a significant brain injury are associated with worse clinical outcomes.

"So, we know that after a significant brain injury, you have increases in in blood sugar that's associated with worse outcomes." (said at 1:56:40)

The claim is supported by extensive observational literature and meta-analyses. A 2025 meta-analysis of 12 cohort studies (16,387 traumatic brain injury patients without preexisting diabetes) found that stress-induced hyperglycemia was significantly associated with a twofold increase in all-cause mortality (RR 2.00, 95% CI 1.72–2.33). Elevated blood glucose levels post-injury are consistently linked to higher mortality and worse neurological outcomes.

2:02:00Tommy Woodsupportedmoderate

Outside of traumatic brain injury, high doses of branched-chain amino acids may impair sleep by competing with tryptophan for uptake into the brain, potentially reducing serotonin and melatonin synthesis.

"And that's interesting because outside of TBI, high doses of branched-chain amino acids may actually impair sleep because they compete for tryptophan uptake into the brain, potentially decreasing serotonin, melatonin production." (said at 2:02:00)

The speaker accurately describes the biochemical mechanism and physiological effects of high branched-chain amino acid (BCAA) levels on sleep. BCAAs (leucine, isoleucine, valine) and large neutral amino acids like tryptophan share the same L-type amino acid transporter (LAT1) across the blood-brain barrier. High circulating BCAA concentrations competitively inhibit tryptophan entry into the central nervous system, thereby reducing the substrate required for brain serotonin and downstream melatonin synthesis. Clinical and observational studies confirm that high BCAA exposure delays sleep onset and is associated with shorter sleep duration and sleep difficulties.

2:34:10Tommy Woodsupportedmoderate

Oral health is significantly linked to cognitive function.

"we didn't talk about oral health and cognitive function, but that's really important, too." (said at 2:34:10)

A large body of epidemiological evidence, including multiple systematic reviews, meta-analyses, and umbrella reviews, demonstrates a significant association between oral health (particularly periodontal disease and tooth loss) and cognitive decline, cognitive impairment, and dementia. Longitudinal cohort meta-analyses consistently show that poor periodontal health and extensive tooth loss are associated with an increased risk of cognitive decline and dementia, although residual confounding and reverse causality remain considerations in observational designs.

1 No source found (not proven false)
1:50:08Andrew Huberman (host)unverifiedvery low

Cortisol levels decrease 20- to 30-fold from morning to night in a healthy individual.

"Like cortisol goes up, cortisol goes down. It drops 20-, 30-fold from the morning until night in a healthy individual." (said at 1:50:08)

No published studies retrieved in this search established a 20- to 30-fold decrease in cortisol levels from morning peak to nocturnal nadir in healthy individuals. While human cortisol follows a robust diurnal circadian rhythm peaking shortly after awakening and reaching a nadir around midnight, literature typically reports a substantially smaller diurnal fold decrease (typically on the order of 3- to 10-fold in serum/plasma or saliva), making the 20- to 30-fold figure unverified in the retrieved records.

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.